RU2445645C2 - Method and apparatus for position determination with extended satellite positioning system orbit information - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: server processor computes a correction between first satellite orbit data and second satellite orbit data, the second orbit data being more accurate than the first orbit data. Spatial components of the correction are then transformed from a first coordinate system to a second coordinate system, where second coordinate system is chosen such that variation of the correction over time in the second coordinate system is smooth. The correction is then sent from the server to a mobile station to enable the mobile station to evaluate more accurate orbit data for the satellite by applying the correction to the first satellite orbit data stored on the mobile station, where the correction, which is encoded in the second coordinate system, is represented by one or more polynomials.

EFFECT: high accuracy of determining position and time of satellites on a mobile station.

74 cl, 7 dwg

Description

This application claims priority on the filing date of application No. 60/857972 for a US patent filed November 10, 2006, entitled “Bit efficient support of extended orbit for GNSS,” application No. 60/886230 for a US patent filed January 23, 2007 g., under the name “Efficient range correction messages for accurate position determination with assisted GPS”, application No. 60/888738 for a US patent, filed February 7, 2007, under the name “Bit efficient support of extended orbit for GNSS”, application no. No. 60/896493 for a US patent filed March 22, 2007, entitled “Method and apparatus for position determination with extended SPS orbit information,” application No. 60/917622 for a US patent filed May 11, 2007, under the name Method and apparatus for position determination with extended SPS orbit information ”and US Patent Application No. 60/939964, filed May 24, 2007, entitled“ Method and apparatus for position determination with extended SPS orbit information ”, all of which are fully incorporated in this application by reference and assigned to its assignee.

FIELD OF THE INVENTION

In general, the present invention relates to a satellite positioning system (SPS), and more particularly, to assist a mobile station in determining a satellite location using an effective message transmission format containing extended satellite orbit correction information in a satellite positioning system.

State of the art

The receiver of a satellite positioning system usually determines its position by calculating the arrival times of signals transmitted simultaneously from several satellites. As part of the messages, these satellites transmit satellite position data and clock timestamp data. The positions of the satellites and timestamps of the clock are usually represented by an almanac or ephemeris data. Ephemeris data provide a very accurate estimate (with an error of ~ 1 m) of satellite positions and clock errors. However, the process of finding and registering satellite signals, reading the ephemeris data transmitted by the satellites, and calculating the location of the receiver based on these data is a lengthy, often requiring several minutes. In many cases, this long processing time is not acceptable, and in addition, severely limits the battery life in miniature portable devices.

For example, in the global positioning system (GPS), the position is determined based on the measurement of the arrival times to the receiver antenna of the global positioning system of the signals of the global positioning system transmitted in broadcast mode from satellites moving in orbits. It is established that one drawback of such a system is the relatively long time required for the registration of signals in certain conditions. Satellite signals cannot be tracked until they are first detected by searching in a two-dimensional search space, the measurements of which are the code delay in phase and the observed Doppler frequency shift. The process of searching for a satellite positioning system by a receiver for recording and demodulating satellite signals is sometimes called an autonomous operating mode, which can be contrasted with an auxiliary operating mode.

To reduce the delay associated with offline operation, information can be provided when registering a particular signal to assist a receiver of a satellite positioning system or global positioning system. Such ancillary information allows the receiver to narrow the search space, which should be examined to detect the signal, by imposing restrictions on the characteristics of the code and frequency. A system that uses a receiver of a global positioning system, supplemented by auxiliary data from an external source of the global positioning system, is usually called a global positioning system with support (AGPS).

One example of a supported global positioning system includes a wireless mobile station (e.g., a cellular telephone) in communication with or in communication with a receiver of the global positioning system, wherein the mobile station is in communication with one or more base stations, also referred to as base transmitters stations or nodes B of a wireless communication network, which, in turn, are in communication with one or more servers, depending on the interface protocol of the overhead communication line location assistance, sometimes referred to as positioning systems (PDEs), mobile location services centers (SMLCs), or the like. Another example of a global positioning system with support includes a mobile station or laptop connected to or in communication with a receiver of the global positioning system, a mobile station or laptop capable of communicating with a data network, such as, but not limited to, the Internet, via which device ultimately communicates with the location assistance server.

The location assistance server receives auxiliary information of the global positioning system from one or more reference receivers of the global positioning system. The location assistance server also has access to a means for determining the approximate position of the mobile station. The location assistance server stores a database of the global positioning system, which contains the reference time, information about the almanac and ephemeris of the satellite’s orbit, information about the ionosphere and information about the satellite’s operational status (“health”). The location assistance server also calculates ancillary information specifically designed to determine the approximate position of the mobile station.

The location of the mobile station in a global positioning support system can be determined on the mobile station (sometimes referred to as the mobile station based positioning mode) using a location assistance server. Continuing the mobile station-based positioning mode when the global positioning system server requires updated process-related data, such as ephemeris data, almanac data related to satellite or base station locations, temporary information for base stations and / or satellites, or source position (for example, but not limited to them, determined using improved trilateration based on a communication line with cellular relays (AFLT)), etc., the subsequent definition s location will result to the data network of the mobile station contact, the excessively loaded network and the mobile station uses energy resources. Alternatively, the location of the mobile station in a supported global positioning system can be determined on a location assistance server using information registered by the mobile station and transmitted back to the mobile station (sometimes referred to as the mobile station supported positioning mode). The satellite orbits in the global positioning system can be modeled as modified elliptical orbits with correction terms to account for various perturbations. Relatively short-term ephemeris data provide a very accurate representation of the satellite’s orbit. For example, bit 17 in word 10 of subframe 2 of the global positioning system is a sign of the “time interval of validity”, which indicates the time interval of validity of the curve used by the control and monitoring segment of the global positioning system when determining the parameters of the ephemeris, while “0” indicates a 4-hour expiration date and “1” means expiration date “more than 4 hours”. In addition, the enhanced navigation mode of the II / IIA block of satellites of the global positioning system guarantees the transmission of accurate ephemeris parameters within 14 days to maintain short-term extended operation. During normal operation, the control and monitoring segment provides daily downloads of navigation (orbital) data for each satellite in order to maintain positioning accuracy with a statistical spherical error of 16 m.

As described, the location assistance server has accurate orbital information available. The action of the ephemeris model and the clock corrections downloaded by the location assistance server typically extends with great accuracy over a 4-hour time interval. To cover a longer period of time, such as a 24-hour period, the location assistance server can send several 4-hour ephemeris models and clock corrections for each of the N satellites in the constellation to the device. However, for a full constellation of satellites (for example, 27 satellites), a large number of eight-bit bytes will be required to describe the positions of the satellites and clock errors. These long messages will increase the length of the processing time, and therefore, are unacceptable for most applications of mobile devices. They will also overburden the communication network.

In addition to the ephemeris data, satellites in the global positioning system also transmit almanac data that can be used to determine satellite positions and clock errors. The almanac data provides a set of ephemeris parameters truncated with reduced (rough) accuracy, as well as inaccurate clock correction parameters. As a result of this, there is a trend of much less accuracy (~ 1 km) of the initial positions of satellites obtained on the basis of almanac data than the positions of satellites obtained on the basis of detailed ephemeris data (~ 1 m). It should be noted that usually the satellite orbits can be represented by an inaccurate set (for example, an almanac) or an exact set (for example, ephemeris) of the parameters of the orbits and clocks of the satellites.

There is a need for a system and method for obtaining extended orbital data for a receiver of a global positioning system to reduce the required download frequency of the almanac and / or ephemeris directly from satellites or from a location assistance server.

SUMMARY OF THE INVENTION

A method and system for assisting mobile stations in determining satellite locations using an effective message transmission format are described. The server calculates the correction between the rough satellite orbital data and the satellite exact orbital data. The coordinate system is chosen so that the change in the correction is essentially smooth over time. The server also approximates the correction with mathematical functions to reduce the number of bits required for transmission to the mobile station. After receiving the coefficients, the mobile station evaluates the mathematical functions using the coefficients and the applicability time (for example, the current time), converts the estimated result into a standard coordinate system and applies the conversion result to rough orbital data to obtain accurate orbital data.

The method and system described in this application provides a unique way to solve problems associated with long-term orbital satellite data. The advantages of the method and system include a smaller file size and small messages sent to the mobile station, as well as higher accuracy in determining the positions and time of satellites. In addition, a hybrid mode of operation is presented to improve forecasts of satellite positions and times.

Other features of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.

Brief Description of the Drawings

The present invention is shown by way of example, and not limitation, in the figures of the accompanying drawings, in which like elements are denoted by like numerals. It should be noted that in this disclosure, references to “one” implementation do not necessarily refer to the same implementation, and such references mean “at least one”.

In the drawings:

figure 1 is a diagram showing an example of a communication system including a server for assisting a mobile station in determining a satellite location;

figure 2 is a diagram showing a coordinate system according to an aspect of the invention;

figure 3 is a sequence diagram showing an example of a method performed by a mobile station;

figure 4 is a sequence diagram showing an example of a method executed by a server;

figure 5 is a sequence diagram showing additional details of the method of figure 4;

6A is a block diagram showing an example of components in a location assistance server;

6B is a block diagram showing an example of components in a mobile station.

Detailed description

A method and system for assisting mobile stations in determining satellite positions and satellite clock errors is described. The positions of the satellites and the errors of the clocks of the satellites are determined using an effective format for transmitting messages containing extended information about the correction of the orbits of the satellites of the satellite positioning system. The method and system described in this application provides a unique way to solve problems associated with long-term satellite orbital data. According to one aspect of the invention, the method allows to reduce file size and to reduce messages sent to the mobile station. The method also improves the accuracy of determining the positions and time of satellites in a mobile station. According to another aspect of the invention, a hybrid mode of operation is introduced to improve forecasts of satellite positions and times.

The number of bits required to maintain corrections for extended orbits and hours is significantly reduced when using correction data computed on the location assistance server and coarse orbital data received at the mobile station. Correction data is the difference between satellite positions calculated on the basis of a rough representation of the satellite’s orbit (for example, but not limited to it, an almanac) and satellite positions calculated on the basis of predicted accurate orbital data (for example, orbital data from a long period of time, greater than that which can be obtained from an artificial satellite (for example, 6 hours or more). Correction data also includes differences between the clock corrections calculated on the basis of coarse orbital data, and clock corrections calculated on the basis of the predicted satellite clock data. Usually these corrections change over time and are unique for each satellite. However, with the appropriate choice of the coordinate system, the change can be relatively smooth. In this case, the corrections are described in time a mathematical function (for example, but not limited to it, a polynomial), while only coefficients are transmitted to the mobile station by the location assistance server.

As used in this application, the term “mobile station” (MS) refers to a device, such as a cellular or other wireless communication device, personal communication system device, laptop or other suitable mobile device capable of receiving and processing satellite positioning system signals. The term “mobile station” is also intended to encompass devices that are associated with a personal navigation device, such as a wireless, infrared, short-range cable connection or other connection, regardless of whether satellite signals are received on the device or on a personal navigation device, auxiliary data and / or position-related processing. In addition, the "mobile station" is supposed to include all devices, including wireless devices, computers, laptops, etc., which are capable of communicating with the server, for example via the Internet, wireless access (WiFi) or another network, and independently on the other hand, in the device, server or other device connected to the network, satellite signals are received, auxiliary data is received and / or position-related processing. Any workable combination of the above is also considered a "mobile station".

The term "rough orbital data" in this application refers to a rough estimate of the position of the satellite and the clock data transmitted from the satellite, for example to the almanac. The term “real-time orbital data” refers to an accurate representation of the satellite’s position and time transmitted from the satellite, such as ephemeris. The term “predicted orbital data” or “accurate orbital data” refers to an accurate estimate of the satellite’s position and time, which have a relatively long validity period compared to accurate real-time orbital data. Predicted orbital data is available on the location assistance server. However, significant bandwidth is typically used to transmit predicted orbital data to a mobile station. Therefore, when transmitting correction data or their approximation, the transmission efficiency often often increases significantly.

1 is a block diagram of a communication system 100 according to an aspect of the present invention. System 100 includes a location assistance server 130 coupled via communication link to one or more mobile stations 120. The location assistance server 130 receives coarse orbital data as well as accurate orbital data and / or predicted orbital parameter files containing predicted orbital data . In one embodiment, the location assistance server 130 receives predicted orbital data over a network 162 from a predicted orbital data provider 110. Network 162 may be a network that supports Internet Protocol (IP) connections, such as the Internet. The location assistance server 130 may include an interface, such as a secure file transfer program (SFTP), for securely transmitting predicted orbital data from a predicted orbital data provider 110.

In one aspect, the predicted orbital data provider 110 generates predicted orbital data every few hours (e.g., 4 hours) to represent orbital data that is reliable over a long period of time (e.g., 6 hours or longer). The location assistance server 130 checks the new data at short intervals (for example, every hour). Predicted orbital data may also include three-dimensional uncertainty values for the predicted satellite coordinates, the uncertainty of the predicted satellite clock corrections, and an indication of predicted outages. Based on the uncertainty and outage information, a user range error (URE) may be computed by the location assistance server 130 and transmitted to the mobile station 120.

The location assistance server 130 receives coarse orbital data from the real-time orbital data provider 150 over the network 164. The real-time orbital data provider 150 may be a global reference network (GRN) gateway or a geographically distributed reference network (WARN) gateway that receives satellite real-time information, including, but not limited to, reference data of the satellite positioning system integrated into the package, navigation messages, page information about “healthy vie ”, almanac and ephemeris. In one embodiment, the network 164 is a network that supports Internet Protocol (IP) connections, and the location assistance server 130 can receive real-time satellite information from the real-time orbital data provider 150 as multicast messages over the Internet Protocol (IP) .

The location assistance server 130 generates correction data 140 based on the predicted orbital data and the rough orbital data. Correction data 140 may be transmitted directly to the mobile station 120 or to the location of a storage device accessible to the mobile station. For example, the correction data 140 may be stored in a storage device locally or remotely connected to the location assistance server 130. Mobile station 120 may receive correction data 140 from data host 160 over network 166 using a file transfer protocol such as FTP (file transfer protocol), HTTP (hypertext transfer protocol), or other suitable network protocols.

In this application, for simplification of consideration, the term “correction data” 140 refers to satellite orbital corrections that can be transmitted from one point to another, transferred in files, transmitted over a broadcast network, or transferred from one place to another using any means of data transmission. The messages generated by the location assistance server 130 have an effective message transmission format that allows the mobile station 120 to determine the positions and readings of the satellite clock with a small number of bits over an extended period of time. Messages from the mobile station 120 provide information for correcting coarse orbital data so that the corrected position of the satellite is accurate within a few meters.

According to another aspect, the location assistance server 130 may also transmit to the mobile station 120 an accuracy estimate (user range error), a correcting ionosphere model, UTC, and satellite health / availability information. This ensures the integrity of satellite data and allows mobile work without the need for receiving and decoding data transmitted by satellites through the air. This also ensures that coarse orbital data that is identical to the coarse orbital data used in the location assistance server 130 is used in the mobile station 120.

It should be noted that the system described above is shown for illustration only and other configurations may exist. For example, as an option, networks 162, 164, and 166 may be direct connections, local area networks, geographically distributed networks, broadcast networks, any suitable wired or wireless networks, computers or computer networks, or combinations thereof, that support data transfer or file transfer.

One skilled in the art will appreciate that coarse orbital data that provides a rough estimate of satellite positions covers a wide range of shapes. In the following description, the latest copy of the broadcast almanac of the global positioning system is proposed for use as a rough estimate of the positions and readings of a satellite clock to facilitate understanding of the concept of the invention. However, all of the following is an illustration of alternative rough orbital data: a previous copy of the broadcast ephemeris of the global positioning system; the last copies of the broadcast almanac or ephemeris "Galileo" or "GLONASS"; a non-broadcasting rough model of satellite positions that follows the same form as the almanac or ephemeris of the global positioning system, Galileo or GLONASS; any subset or extension of Kepler’s parameters used in the almanac and ephemeris formats of the global positioning system, “Galileo” and “GLONASS”; any non-Keplerian representations of the orbits of the satellites; and other predicted orbital data that worsen over time. In addition, it should be clear that the relevant information related to other satellite navigation systems can also be applied within the framework of the disclosed methodology. The present invention includes any and all methods for describing an inaccurate orbit. One skilled in the art should understand that the technique is applicable regardless of the form that the rough estimate takes.

In some embodiments, coarse orbital data may be provided by the location assistance server 130 to the mobile station 120. In addition to transmitting a rough estimate of the satellite positions to the mobile station 120, the location assistance server 130 is able to include reference time in an auxiliary message to the mobile station. According to this aspect of the invention, the location assistance server 130 obtains a reference time from a network time server or from global positioning system data received from individual reference receivers (e.g., a geographically distributed reference network or a global reference network). This reference time information may be attached to a message transmitted to the mobile station 120, which contains a rough estimate of the satellite’s position. The location assistance server 130 may also provide algorithms that can improve the accuracy of the reference time provided by the network time server, and transmit this more accurate time to the mobile station 120.

It should be noted that the mobile station 120 can directly receive the reference time, regardless of the location assistance server 130, from a packet-switched network, which may or may not be synchronized with the time of the global positioning system (for example, from a network time server or from communication network based on multiple access code division multiple access (CDMA)). In this way, the mobile station 120 obtains an estimate of the global reference time, for example, the global positioning system time, universal coordinate time (UTC), WWO time, etc.

Figure 2 shows an example of a coordinate system based on which correction data 140 is calculated. Track 21 is an actual satellite orbit track, which can be substantially estimated using accurate orbit predictions. Track 22 is an orbit track estimated using rough orbital data, such as, but not limited to, a broadcast almanac. At any point in time, there is a spatial difference between the location of the satellite, which is indicated by the broadcast almanac, and the location, which is indicated by accurate forecasts of the orbit. This difference can be encoded in a coordinate system 23, which is a coordinate system having a origin and axes that move with the satellite’s body. The “error signal” expressed in the orthogonal coordinate system 23, which is the difference between the accurately predicted position of the satellite and the position of the satellite based on the almanac, becomes an essentially smooth curve. The change in the error signal is essentially smooth in time, so that there are no kinks or sharp turns in the error signal when it is presented as a function of time. In the embodiment of FIG. 1, the error signal generates correction data 140. The fundamental method of expressing the error signal in the selected coordinate system effectively minimizes the degree of polynomials needed to express these “error signals” with any given accuracy.

In one aspect, the correction data 140 consists of four measurements of information: three spatial measurements (represented by three axes of the coordinate system) for describing a satellite position error and a time measurement (fourth measurement) that describes the correction of satellite clock readings.

The three axes of the coordinate system 23 are: Ra , which is a unit vector directed from the inaccurate position of the satellite (for example, the position of the satellite determined on the basis of the broadcast almanac) to the starting point. Since the center of the earth is the starting point in typical situations, this axis is interpreted as “radial”. One skilled in the art should understand that the starting point can be any point (for example, inside, above, on or near the surface of the Earth) that can be determined with reasonable accuracy.

The other axis is Xt : the “transverse track", which is defined as Xt = Ra × Vel / | Ra × Vel |. Vel is an almanac-based satellite velocity vector and “×” stands for vector product. Therefore, the vector Xt is perpendicular to the radial vector Ra and to the direction of motion of the satellite.

The third axis is At : a “track in the direction of travel,” which is defined as At = Xt × Ra . The vector At is almost parallel to the satellite velocity vector ( Vel ), but not quite. This is because the satellite’s velocity vector is not exactly orthogonal to Ra due to the eccentricity of the orbit (for example, the satellite’s orbit is elliptical in nature, not circular). Since over time the radius of the satellite’s orbit increases and decreases, the satellite velocity vector Vel usually has a component in the radial direction Ra .

The three axes of the coordinate system 23 defined above are a function of time, since they depend on the instantaneous position of the satellite in the direction of its orbit. Among other motions, such as the orbits of the Earth’s satellites, the radial vector Ra and the track vector At in the direction of motion rotate 360 ° when expressed in a geocentric system of 24 XYZ coordinates associated with the Earth. Note that these axes are calculated using an almanac-based satellite position estimate. This allows the axes of the coordinate system 23 to be calculated using the location assistance server 130 before calculating the almanac corrections. In the example of the coordinate system 23, the order in which the axes are calculated is essential for the proper orientation of the coordinate system. Therefore, the radial vector Ra is calculated first, the vector Xt of the transverse track is calculated second, and the vector At of the track in the direction of travel is calculated last.

The orientation of the axes defined above is different for each satellite. We can write unit vectors in the form of Ra (PRN, t), At (PRN, t), Xt (PRN, t) and make them dependent on the pseudo-random number (PRN) of the satellite and t, which are respectively the number of the satellite and the current time in explicit form. However, for the sake of simplicity of notation, in the following considerations, these dependencies remain implied.

Other coordinate systems can also be used to correct rough orbital data, such as, but not limited to, a radius / transverse track / speed coordinate system (other than ( Ra , At , Xt ) described above); XYZ 3D geocentric, Earth-related coordinate system for calculating differences, or (polar) elevation / azimuth coordinate system.

One skilled in the art will appreciate that the coordinate system ( Ra , At , Xt ) (obeying the well-known left-hand rule) is an illustrative and one preferred approximation, but that a wide range of other axis systems are encompassed by the present invention. A characteristic feature of these axis systems is that for them there is a tendency to have two spatial dimensions with significantly less stringent accuracy requirements compared to the third. In the example of the coordinate system 23 ( Ra , At , Xt ), usually for At and Xt there are weaker accuracy requirements (for example, 1/7) compared to Ra . The coordinate system can be orthogonal or non-orthogonal. To correct rough orbital data, the non-orthogonal coordinate system can be any axis system in which one of the axes always forms a relatively small angle relative to the axis Ra , even if it has a different origin than the coordinate system 23 ( Ra , At , Xt ). It will include, for example, a coordinate system in which one axis is Ra , but the other two axes are the azimuth and elevation angle of the satellites, as well as any other options for the other two axes.

In addition, any axis system in which some axis is parallel to a line extending from a point near the estimated satellite location to a point near the location of the receiver on Earth falls within the scope of the present invention. Although figure 2 shows the axis Ra , pointing to the center of the earth, an axis that points to any point near the receiver on the ground or any other identifiable starting point falls within the scope of the present invention.

In addition, within the scope of the invention, the location of the origin of the coordinate system 23 ( Ra , At , Xt ) can be changed. The beginning at the location of the satellite is a matter of mathematical convenience. In particular, the beginning specified in the actual or accurately predicted location of the satellite (as opposed to evaluating the location of the satellite, as in the coordinate system 23 ( Ra , At , Xt )) is within the scope of the invention.

Over a period of time (for example, a 6-hour time period), each of the three spatial dimensions of the correction data can be expressed as a function of time in a selected coordinate system, such as a coordinate system 23 ( Ra , At , Xt ). Theoretically, correction data can be accurately represented by polynomials of infinite degree. However, in practice, correction data can be approximated by polynomials of a relatively low degree, for example, a sixth, seventh, or other low degree. Therefore, a large number of polynomial terms and related coefficients are truncated; only a small relative part of the polynomial terms and their associated coefficients is used as an approximation to the correction data. In addition to spatial corrections, a low degree polynomial (for example, first degree or any suitable low degree) can be used to describe the clock correction parameters, which are an approximation of the difference between the time stamp of the clock in rough orbital data and the predicted clock error. Other predictions of accurate clock readings that are available in the location assistance server 130 can also be used as a predicted clock error, such as real-time orbital clock information, if any.

One skilled in the art will appreciate that the present invention comprises decomposing correction data into a series of functions with the possibility of improving accuracy in decomposition, since more functions are used. There is no need for a number of functions to be of increasing powers of x , as a result of which the correction data will be presented in the form of a polynomial. One of ordinary skill in the art should understand that correction data can also be decomposed into another series of functions, including harmonic function, Hermite polynomials, Legendre polynomials, cosine and sinusoidal functions (Fourier expansion), and Kepler orbital function coefficients. This list is illustrative but not exhaustive. The decomposition of correction data into any number of functions is within the scope of the invention.

Four spatial and temporal sets of polynomial coefficients are sent to the mobile station 120 along with the information needed to associate these coefficients with a particular satellite, a specific time interval, and a specific copy of the rough orbital data. Mobile station 120 receives a new copy of the coarse orbital data at predetermined intervals (for example, approximately once a week or at other suitable time intervals). The location assistance server 130 calculates correction data using the same rough orbital data version as the version used by the mobile station 120. Therefore, rough orbital data can be used on the mobile station 120 that is registered with it or which are transmitted by the location assistance server 130, provided that the correction data is applied to the corresponding rough orbital data that is used in the location assistance server 130 for and definition of amendments.

Figure 3 shows an example of operations performed by a mobile station (MS) 120. Note that the processes shown in figure 3 can be performed by information processing logic, which may include software, hardware, or a combination of both. If only the mobile station 120 has polynomial coefficients and the time of applicability, the mobile station can reconstruct accurate predictions of satellite position and clock error. For any particular point in time during the period of applicability of the coefficients, the mobile station 120 can find the satellite position and clock error within a given accuracy range.

At block 31, the mobile station 120 receives coarse orbital data (eg, almanac data) from satellites within sight or from a location assistance server 130. It is often preferable and more efficient that the mobile station 120 receives coarse orbital data from the location assistance server 130, since downloading such data from satellites can take many minutes. The location assistance server 130 may provide the coarse orbital data in the message / file with the correction data to the mobile station 120. It will be appreciated that the “correction data” related to the mobile station 120 may be an approximation to the correction calculated on the location assistance server 130. At block 32, the mobile station 120 generates satellite positions in geocentric Earth-related (DSS) coordinates using its copy of the rough orbital data. The satellite positions calculated on the basis of rough orbital data and presented in a standard coordinate system, for example, in geocentric, Earth-related coordinates, are denoted by Pos _Alm (in this case, the subscript “Alm”, which symbolizes the “almanac”, is used as an example of rough orbital data). At block 33, the mobile station 120 receives the coefficients of one or more series of mathematical functions from the location assistance server 130. At block 34, the mobile station 120 reconstructs the spatial correction data from the rough orbital data for the applicability time (eg, current time) by evaluating the mathematical functions for the current time using the received coefficients. In block 35, the mobile station 120 converts the spatial corrections found in block 34 from a coordinate system (for example, coordinate system 23 ( Ra , At , Xt ) from Figure 2) to geocentric, Earth-related coordinates. Converted amendments are indicated by Pos _Cor . After that, in block 36, the mobile station 120 calculates the locations (Pos _Sat ) of the satellites in geocentric Earth-related coordinates by calculating Pos _Sat = Pos _Alm + Pos _Cor . In block 37, the mobile station 120 performs the same operations as in blocks 34 and 36 to determine the exact error of the clock. It is understood that the operations of the mobile station may be carried out in a manner different from that described above, and additional operations may also be performed. For example, in block 36, instead of calculating Pos _Sat = Pos _Alm + Pos _Cor , the application of Pos _Cor in the distance space, R _Sat = R _Alm + R _Cor , where R is the calculated distance from the mobile station 120 to the satellite, can be selected.

4 shows an example of operations performed by the location assistance server 130. Note that the processes shown in FIG. 4 may be performed by information processing logic, which may include software, hardware, or a combination of both. The location assistance server 130 calculates polynomial coefficients that describe the correction data during subsequent operations.

At block 410, the location assistance server 130 obtains accurate orbital data for satellite orbits and clock errors, for example, from satellite broadcast signals or from an external data provider. Accurate orbital data are valid over a period of validity. In block 420, the location assistance server 130 receives coarse orbital data in a format supported by a particular satellite navigation system. At block 430, the location assistance server 130 determines whether to divide the validity period into several N-hour validity intervals or to use the entire validity period as one valid validity period. In this case, the expiration time interval is the time period for which polynomial coefficients are calculated to describe the correction data for this time period. An example of a shelf life is 4-6 hours, although other time periods can also be used. If the location assistance server 130 has accurate orbital data with a long validity period, then the location assistance server can divide the accurate orbital data into a plurality of validity time intervals to improve match accuracy. At block 440, for each N-hour validity interval, the location assistance server 130 performs the operations described below in FIG. 5 to calculate correction data and approximate it. At block 450, the location assistance server 130 transmits the correction data approximation to the mobile station 120.

Referring to FIG. 5, in block 510, the location assistance server 130 uses accurate orbital data to form a time sequence of satellite positions in geocentric Earth-related (DSS) coordinates. These satellite positions are denoted by Pos _Sat. In block 512, the location assistance server 130 uses coarse orbital data to calculate satellite positions in geocentric, Earth-related coordinates. These satellite positions are denoted by Pos _Alm . At block 514, the location assistance server computes correction vector (Pos _Cor ) vectors in geocentric, Earth-related coordinates by calculating Pos _Cor = Pos _Sat -Pos _Alm . At block 516, the location assistance server 130 uses the satellite position Pos _Sat to compute the unit vectors Ra , Xt, and At in the orthogonal coordinate system 23 or other coordinate systems described above. At block 518, the time sequence of the correction component along the radial axis Ra is found by calculating the scalar product Ra _Cor = Pos _Cor · Ra . At block 520, the time sequences Xt _Cor and At _{Cor of the} transverse track and the track in the direction of travel are likewise calculated. At block 522, the correction data for the clock error is calculated as CB _Cor = CB _Sat —CB _Alm , where CB _Sat and CB _Alm are clock corrections using an accurate clock model and a rough estimate from the clock model, respectively.

At block 524, the location assistance server 130 may scale and / or normalize the time axis of the polynomial interpolation to improve interpolation characteristics. It is assumed that the location assistance server 130 and the mobile station 120 use the same scaling and / or normalization factors to correctly restore the correction data in the mobile station software.

At block 526, the location assistance server 130 finds polynomial coefficients for interpolating the corrections Ra _Cor , At _Cor and Xt _Cor , radial, for the track in the direction of travel and the transverse track. The polynomial coefficients (Ra ₀ , Ra ₁ , ... Ra _j ) for Ra _Cor are chosen so that Ra ₀ f ₀ (d) + Ra ₁ f ₁ (d) + ... + Ra _j f _j (d) is a good approximation to Ra _Cor , where d is the correction data point and f ₀ , f ₁ , ... f _j are interpolating functions. The coefficients can be selected from the condition of the minimum mean square error of the polynomial approximations Ra _Cor . The location assistance server 130 similarly finds polynomial coefficients for Xt _Cor and At _Cor so that these coefficients Xt ₀ , Xt ₁ , Xt ₂ , ..., Xt _k , At ₀ , At ₁ , ..., At _m provide good approximations to Xt _Cor and At _Cor . Finally, at block 530, the location assistance server 130 finds the coefficients of the interpolation functions to correct the CB _Cor of the clock error. It is understood that the number of coefficient terms for representing corrections in each of the spatial and temporal dimensions may not be the same. More coefficients for a measurement usually correspond to higher accuracy when presenting correction data in that measurement.

Operations from blocks 510-530 are repeated if there are several N-hour shelf life intervals during the validity period. The order of operations may differ from that described above and additional operations may be included.

The correction data generated by the location assistance server 130 of FIG. 1 may be global or local. When the location of the mobile station 120 is completely unknown or the location cannot be estimated with an accuracy of several hundred kilometers, the location assistance server 130 creates a global message for the mobile station. To obtain accurate satellite positions, global messages can be sent to mobile stations located on Earth anywhere. Local communications are more concise, but they are accurate only within a radius of several hundred kilometers from some intended reference point on the surface of the Earth. Therefore, shorter local messages can be sent when it is known in advance that the mobile station is within a few hundred kilometers. When the location of the mobile station is unknown, global messages may be sent to the mobile station. The difference between a global message and a local message is described below.

In global communication, the center of the earth is used as the starting point of the coordinate system ( Ra , At , Xt ). Almanac errors have four independent dimensions (three spatial dimensions and a clock error), the global message includes four polynomials, three to correspond to the orthogonal spatial components of the satellite position error, and a fourth polynomial to more accurately describe the clock error.

In local communication, a point on the surface of the Earth is used as the starting point of the coordinate system ( Ra , At , Xt ). Typically, in the location assistance server 130, an estimate of the current location of the mobile station is used as a starting point (for example, the location of the mast of the cellular antenna with which the mobile station is in communication). The local message contains a single polynomial selected for correction. One-dimensional correction includes correction for the spatial distance to the satellite (also called pseudorange), as well as correction of clock errors. Since only one polynomial is sent, the local message is much shorter than the global message.

The pseudorange correction is calculated for the starting point, which ideally is as close as possible to the place where the mobile station is actually located. Provided that the mobile station is located at a distance of about 100 km from the estimated starting point, the positioning result is quite accurate. Accuracy is slowly deteriorating as the true position of the mobile station differs by more than 100 km from the estimated starting point. The mobile station can determine the deterioration in positioning accuracy by first calculating its location and then comparing the location with the starting point from the correction data.

According to another aspect, a combination of orbital data may be used in the mobile station 120 of FIG. 1 to determine satellite positions and clock readings. In some embodiments, the mobile station 120 receives real-time orbital data (eg, ephemeris) in addition to the correction data. In the case of a single satellite, mobile station 120 may use real-time orbital data for one time period, adjusted orbital data (which contains correction data applied to rough orbital data) for another time period, and a combination (e.g., weighted average) of both data for one time period. Real-time orbital data for one satellite, adjusted orbital data for another satellite, and a combination of both data for another satellite can be used to determine their location across multiple satellites at mobile station 120. One skilled in the art will appreciate that the various combinations described above are only illustrative. Any combination of time or various satellites, real-time orbital data and adjusted orbital data may be used by mobile station 120.

In one aspect, the mobile station 120 may use real-time decoded orbital data from satellites whenever real-time orbital data is available. Real-time orbital data is usually more accurate than earlier predicted orbital data, which may gradually degrade over time. Therefore, the corrected orbital data, which approximate the predicted orbital data, also gradually deteriorate over time. In addition, real-time orbital data may contain new satellite information unknown during the execution of forecasts (for example, information about the "health" and integrity of the satellite). However, sometimes real-time orbital data is not available to the mobile station 120 due to the lack of line of sight, shadowing, or other reception problems that prevent the mobile station 120 from receiving satellite broadcasts. When real-time orbital data is not available, mobile station 120 may switch to the correction data described above in FIGS. 2-5 above to determine the location of satellites. Therefore, depending on the availability of real-time orbital data, mobile station 120 may use adjusted orbital data for one time period and real-time orbital data for another time period. To determine its own position at any time, the mobile station 120 may use the corrected orbital data from one or more satellites and real-time orbital data from one or more other satellites.

The preceding paragraph describes the case where the adjusted orbital data could be replaced by available orbital data in real time to extend the reliability of orbital data in real time. For example, after the ephemeris is no longer reliable (+/- 2 hours from the ephemeris era), the mobile station 120 may switch back to the corrected orbital data. Alternatively, real-time orbital data from an early time period can be used to improve the accuracy of the corrected orbital data. For example, the mobile station 120 may use real-time orbital data to determine the degree to which a parameter changes for a future time period of the corrected orbital data that can be used when the real-time orbital data is unavailable (or insolvent). This is especially useful for satellite watches, since the time stamp of the clock is not as predictable as the satellite trajectory. In the simple case, the corrected clock readings of the artificial satellite can be estimated by comparing with the broadcast parameters of the satellite clock in real time (for example, from the navigation subframe 1 based on the global positioning system) to determine the degree of change in the readings of the adjusted clocks. Changing the parameters (for example, including differential shift and slope) can be applied to the corrected information about the clock for use when the clock is not available in real time. In a more complex case, a change in parameters can be made for all corrected orbital data, including the positions of the satellites in three spatial dimensions and the clock of the satellites.

In addition, real-time orbital data and predicted orbital data can be weighted according to their accurate estimates. The mobile station 120 may appropriately weight the available satellite measurement results in a solution for its position and take into account the deteriorating accuracy of the predicted data. Accuracy estimates for real-time orbital data and predicted orbital data are known as “estimating the error of accurate or short-term predicted data” and “estimating the error of long-term predicted data”, respectively. For example, the almanac contains an estimate of the uncertainty in the form of a user range error (calculated or provided by the location assistance server 130), and the real-time ephemeris contains an estimate of the uncertainty in the form of a user range accuracy (provided, for example, by the control and monitoring segment of the global positioning system). User range accuracy (URA) is usually a couple of meters, and user range error (URE) can be tens of meters after a couple of days. For example, both error estimates can be used as weights in a weighted least squares model. Weights can be calculated as: W _{(short-term predicted orbit)} = 1 / URA ² and W _{long-term predicted orbit)} = 1 / URE ² .

In particular, satellite measurements with smaller satellite position errors (represented by the URA in the above example) are weighted with a higher weight than satellite results with larger satellite position errors (represented by the URE in the above example). Satellite measurement results for a position, speed, time solution, or any combination of a position / speed / time solution can be weighted. A weighted position / speed / time solution can be calculated based on satellite measurements using a weighted least squares model or Kalman filter, or any other linear, linearized or non-linear estimation method.

To calculate the total error of the measurement results, during position / speed / time calculations at the mobile station 120, estimates of satellite positioning errors (real-time ephemeris (user range accuracy) or predicted orbital errors (user range error) are combined with measured pseudorange errors (due to signal level , atmosphere, quantization, conversion of the radio frequency signal into digital form, etc.) In other words, the total pseudorange error and the mobile station 120, the variance of the total measurement error = error variance satellite positioning + variance measurement errors.

In addition, when at the mobile station 120, a set of real-time orbit information and predicted orbits from several satellites is used to determine its own location, an additional satellite measurement result can be used to find a solution for the predicted satellite clock error. This additional satellite measurement result can be real-time orbital data for a satellite and can be used to estimate the predicted clock error of the same satellite. Alternatively, the additional satellite measurement result can be real-time orbital data for the first satellite and can be used to estimate the predicted clock error of the second satellite. The predicted clock error can be removed from the readings of the corrected hours to increase the accuracy of the readings of the corrected hours calculated at the mobile station. Thus, real-time orbital data and satellite clock correction data can be used to make real-time changes to information about the predicted satellite clock readings.

Because the predicted satellite clock reading deteriorates faster than the predicted satellite position, an additional satellite measurement result can be used in conjunction with the predicted satellite position to calculate the predicted satellite clock errors and make changes to the predicted clock readings for future use. Similarly, if the current real-time orbital data is available for at least one additional satellite within sight, then this real-time data can be used together with the results of measurements of the pseudorange of this satellite and the rate of change of range to calculate the predicted error of the satellite clock of another satellite in limits of visibility. For a two-dimensional position estimate (there is some information about the angular height), at least four satellites are needed within sight to estimate the predicted satellite clock error for one satellite. For a three-dimensional position estimate, at least five satellites are needed within sight to estimate the predicted satellite clock error for one satellite. Each additional satellite can be used to estimate another predicted error of the satellite clock. For example, in the three-dimensional case (with four unknowns), if measurement results from 7 satellites are available, the predicted errors of satellite clocks can be estimated for three satellites.

Figure 6A shows an example structural diagram of the location assistance server 130 of Figure 1. Location assistance server 130 includes a storage device 604 and processor 605. Location assistance server 130 also includes a secure interface 61 for securely receiving predicted orbital data from an external data provider, a receiver interface 62 for receiving broadcast data (e.g., an almanac), as well as information transmitted over the network (e.g., a forecast orbital data), and a transmitter interface 65 for transmitting coefficients to mobile station 120 for determining predicted satellite orbital data. The transmitter interface 65 may transmit coefficients over wired and wireless networks, via broadcast means, or any suitable means of transmitting data.

In one embodiment, the location assistance server 130 may also include a correction unit 63 for calculating the differences (“corrections”) between the rough orbital data and the predicted orbital data. The location assistance server 130 may also include an approximation unit 64 for calculating the approximation of the correction using a coordinate system that is selected so that the change in the correction is substantially smooth over time (for example, a coordinate system 23 ( Ra , At , Xt ) from figures 2). In one embodiment, the approximation is calculated by interpolating the correction data points using one or more lower order mathematical functions. The coding unit 610 encodes the approximation for transmission to the mobile station 120.

6B shows an example block diagram of components of a mobile station 120. The mobile station 120 includes a storage device 608 and a processor 609. The mobile station 120 also includes a receiver interface 66 for receiving coefficient sequences from the location assistance server 130. The receiver interface 66 also receives coarse orbital data and / or orbital data in real time, such as almanacs, ephemeris and / or other satellite position and timestamp information, from satellite broadcast stations, from a location assistance server 130, or from other data sources. The receiver interface 66 may receive coefficients over wired and wireless networks, via broadcast means, or any suitable means of transmitting data. The mobile station 120 includes a decoding unit 620 for decoding sequences of coefficients sent from the location assistance server 130. In one embodiment, the mobile station 120 may include an evaluation unit 602, a conversion unit 68, and a recovery unit 67. The evaluation unit 602 evaluates the mathematical functions using coefficients and applicability time (eg, current time). Transform unit 68 converts the estimated result from the coordinate system used by the location assistance server 130 (for example, from the coordinate system 23 ( Ra , At , Xt ) of FIG. 2) into a geocentric, Earth-related coordinate system. Then, the recovery unit 67 restores the predicted orbital data by applying the conversion result to the rough orbital data.

Depending on the application, the techniques described in this application can be implemented by various means. For example, the above components of the location assistance server 130 and the mobile station 120 may be implemented in hardware, firmware, software, or a combination thereof. If implemented in hardware, the processing units can be implemented within one or more specialized integrated circuits (ASICs), processors for digital signal processing (DSP), devices for digital signal processing (DSPD), programmable logic devices (PLD), logic circuits (FPGA), programmable in the field, processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described in this application, or combinations of them.

If implemented by firmware or software, the techniques may be implemented by modules (e.g., procedures, functions, etc.) that perform the functions described above. Any machine-readable medium that actually contains commands can be used to implement the techniques described in this application. For example, referring again to FIGS. 6A and 6B, where software codes can be stored in a storage device (e.g., storage device 604 of location assistance assistance server 130 and storage device 608 of mobile station 120) and executed by a processor (e.g., processor 605 of assistance server 130 location and processor 608 of mobile station 120). The storage device may be implemented in the processor or as external to the processor. As used herein, the term “storage device” refers to long-term, short-term, volatile, non-volatile, or other type of storage device of any type and is not limited to any particular type of storage device or the number of storage devices or the type of medium on which the storage device is based.

The method and device described in this application can be used in conjunction with various satellite positioning systems (SPS) or global navigation satellite system (GNSS), such as, but not limited to, the global positioning system of the United States, the Russian GLONASS system, European Galileo system, any system that uses satellites from a combination of satellite systems, or any satellite system that will be developed in the future. In addition, the disclosed method and apparatus can be used in conjunction with positioning systems that use pseudoliths or a combination of satellites and pseudoliths. Pseudo-latches are terrestrial transmitters that transmit a pseudo-random code or another range code (the same as in the global positioning system, or a cellular signal of a code division multiple access system (CDMA)), modulated on an L-band carrier signal (or on a different frequency ), which can be synchronized with the time of the global positioning system. Each such transmitter can be assigned a unique pseudo-random code in order to provide identification by the remote receiver. Pseudoliths are useful in situations where the signals of the global positioning system from orbiting satellites may be unavailable, for example, in tunnels, mines, buildings, urban gorges and other closed areas. Another implementation of pseudoliths is known as beacons. The term "satellite" used in this application is intended to include pseudoliths, equivalents of pseudoliths, and possibly others. The term "global positioning system signals" used in this application is intended to include signals from pseudoliths or pseudolith equivalents similar to signals of a global positioning system.

The positioning methods described in this application can be used for various wireless communication networks, such as a wireless regional area network (WWAN), a wireless local area network (WLAN), a wireless personal area network (WPAN), etc. The terms “network” and “system” are often used on an equal footing. A wireless regional area network (WWAN) can be a code division multiple access (CDMA) network, a time division multiple access network (TDMA), a frequency division multiple access network (FDMA), orthogonal frequency division multiple access (OFDMA) network ), a single-carrier frequency division multiple access network (SC-FDMA), etc. A code division multiple access (CDMA) network may implement one or more radio access technologies (RAT), such as third generation code division multiple access (CDMA-2000), code division multiple access (W-CDMA), etc. . Third Generation Code Division Multiple Access (CDMA-2000) covers the IS-95, IS-2000, and IS-856 time standards. A time division multiple access (TDMA) network may implement a global mobile communications system (GSM), a digital modification of an advanced mobile telephone system (D-AMPS), or some other radio access technology. The Global System for Mobile Communications (GSM) and Code Division Broadband Multiple Access (W-CDMA) are described in consortium documents called “3rd generation partnership project” (3GPP). The third generation code division multiple access system (CDMA-2000) is described in the consortium’s documents as “3rd generation partnership project 2” (3GPP2). 3GPP and 3GPP2 documents are publicly available. A wireless local area network (WLAN) can be an IEEE 802.11x network, and a wireless personal area network (WPAN) can be a Bluetooth network (using technology for wireless data exchange between various devices), IEEE 802.15x, or some other type. The methods can also be applied to any combination of a wireless regional area network (WWAN), a wireless local area network (WLAN) and / or a wireless personal area network (WPAN).

Although the present invention has been described with reference to specific examples of features, it is obvious that various modifications and changes can be made to these features without departing from the broad essence and scope of the invention set forth in the claims. Therefore, the description and drawings should be considered as illustrative and not restrictive.

Claims (74)

1. A method of assisting a mobile station in acquiring satellite orbital information comprising the steps of:
calculating a correction by the server processor between the first satellite orbital data and the second satellite orbital data, the second satellite orbital data being more accurate than the first satellite orbital data; and
converting the spatial components of the correction from the first coordinate system to the second coordinate system using the server processor, the second coordinate system being chosen so that the correction in the second coordinate system is essentially smooth over time, and transmitting the correction encoded in the second coordinate system from the server to a mobile station to enable the mobile station to estimate more accurate orbital data for the satellite by applying an amendment to the first orbital satellite data stored on the mobile station, and the correction encoded in the second coordinate system is represented by one or more polynomials. 2. The method according to claim 1, additionally containing phase, in which:
approximate the correction in the second coordinate system to reduce the number of bits used for transmission to the mobile station. 3. The method according to claim 2, in which said approximation of the amendment comprises the step of:
using the coefficients of one or more polynomials as an approximate correction. 4. The method according to claim 1, in which the polynomials are one or more Hermite polynomials or Legendre polynomials. 5. The method according to claim 1, in which the second coordinate system has axes that move with the satellite. 6. The method according to claim 5, in which the second coordinate system contains a radial axis, while the radial axis is parallel or coinciding with the line that connects the starting point with the estimated position of the satellite. 7. The method according to claim 6, in which the second coordinate system further includes an axis of the transverse track perpendicular to the radial axis and the direction of motion of the satellite. 8. The method according to claim 2, in which said approximation of the amendment comprises the steps of:
using the location of the mobile station as a starting point for a second coordinate system; and
transmitting the approximated correction from the server computing platform to the mobile station as one-dimensional data, the correction including the spatial measurement combined with the clock correction. 9. The method according to claim 2, in which said approximation of the amendment comprises the steps of:
use the center of the earth as a starting point for a second coordinate system; and
the approximated correction is transmitted as four-dimensional data, wherein the correction includes three spatial measurements of the second coordinate system and a time measurement for correcting the clock. 10. The method according to claim 1, in which the correction in one spatial dimension is essentially more accurate than in other spatial dimensions. 11. The method according to claim 1, further comprising stages in which:
receive the reference time from the time server; and
transmit the reference time along with the evaluation of the satellite positions from the server to the mobile station. 12. The method according to claim 11, further comprising stages in which:
increase the accuracy of the reference time received from the time server; and
the reference time is attached to the evaluation of satellite positions in order to form a message for transmission to a mobile station. 13. The method according to claim 1, additionally containing stages in which:
approximate the correction for the time stamp of the satellite; and
transmit the approximate correction for the timestamp of the satellite from the server to the mobile station to determine the error of the satellite clock. 14. The method according to claim 1, additionally containing phase, in which:
transmitting the correction to the file data host for access by the mobile station. 15. A method for determining satellite orbital information, comprising the steps of:
converting the correction for satellite orbital data from a first coordinate system to a second coordinate system using a processor; and applying the converted correction to the first satellite orbital data using a processor to estimate more accurate satellite orbital information, the converted correction being one or more polynomials. 16. The method according to clause 15, in which the correction in the first coordinate system has a substantially smooth change in time. 17. The method according to clause 15, in which the correction in the first coordinate system has a higher accuracy in one spatial dimension than in other spatial dimensions. 18. The method according to clause 15, in which the axis of the first coordinate system rotates with the movement of the satellite. 19. The method according to clause 15, in which one or more axes of the first coordinate system are determined by the position or movement of the satellite. 20. The method according to clause 15, in which the conversion and application are performed by the mobile station. 21. The method according to clause 15, further comprising stages in which:
on the server calculate the correction for the satellite orbital data, and the server contains a processor; and
on the server using the processor, the correction is converted from the second coordinate system to the first coordinate system. 22. A method for determining satellite orbital information by a mobile station, comprising the steps of:
accepting the correction for the first satellite orbital data at the mobile station, wherein the first orbital data is received by the mobile station, wherein the correction is represented by one or more polynomials;
using the processor, convert the correction represented by one or more polynomials from the first coordinate system to the second coordinate system, while the correction presented in the first coordinate system has higher accuracy in one spatial dimension than in other spatial dimensions; and
apply the correction to the first orbital data to evaluate more accurate satellite orbital information. 23. The method of claim 22, wherein the first coordinate system includes three orthogonal axes. 24. The method of claim 22, wherein the first coordinate system includes non-orthogonal axes. 25. The method according to item 22, in which the first coordinate system includes a radial axis, the radial axis being parallel or coinciding with the line that connects the starting point with the estimated position of the satellite. 26. The method according A.25, in which the starting point is the center of the Earth. 27. The method according A.25, in which the starting point is the estimated location of the mobile station. 28. The method according to item 22, in which the amendment is represented by the coefficients of one or more polynomials for each of the spatial dimensions. 29. The method of claim 28, wherein the polynomials are one or more Hermite polynomials or Legendre polynomials. 30. A method for determining satellite orbital information by a mobile station, comprising the steps of:
receive the first orbital satellite data at the mobile station from the ephemeris information obtained from the satellite;
receiving correction data for the first satellite orbital data at the mobile station, the correction data being one or more polynomials;
using the processor, convert correction data represented by one or more polynomials from the first coordinate system to the second coordinate system, while the first coordinate system is selected to smoothly change the correction over time; and
apply correction data to the first orbital data using a mobile station processor to estimate more accurate satellite orbital information. 31. The method according to item 30, further containing a stage on which:
determine the position and time stamp of the satellite based on the correction data. 32. The method according to claim 30, wherein said receiving correction data comprises the steps of:
receiving a sequence of coefficients of one or more polynomials for at least one axis of the first coordinate system; and
evaluate one or more polynomials using a mobile station processor using a sequence of coefficients and an applicability time to obtain correction data. 33. The method according to p, in which the polynomials are one or more Hermite polynomials or Legendre polynomials. 34. The method according to item 30, in which the first coordinate system contains one or more axes that move with the satellite. 35. The method according to clause 34, in which the first coordinate system includes a radial axis, while the radial axis is parallel or coincident with the line that connects the starting point with the estimated position of the satellite. 36. The method according to clause 30, in which the first coordinate system further includes an axis of the transverse track perpendicular to the radial axis and the direction of motion of the satellite. 37. The method according to clause 30, further comprising stages in which:
using the location of the mobile station as a starting point for the first coordinate system; and
receiving the coefficients of one or more polynomials at the mobile station, the coefficients representing one-dimensional data that include a spatial measurement combined with a clock correction. 38. The method according to clause 30, further comprising stages in which:
use the center of the earth as a starting point for the first coordinate system; and
the coefficients of one or more polynomials are received at the mobile station, the coefficients representing four-dimensional data, which include three spatial measurements of the first coordinate system and a time measurement for adjusting the clock. 39. The method according to claim 30, wherein the correction data is presented in the first coordinate system with higher accuracy in one spatial dimension than in other spatial dimensions. 40. The method according to clause 30, further containing a stage in which:
receive a reference time from one of the following: a network time server, a location assistance server, a packet data network, or from global positioning system data received from a reference receiver. 41. A server system for generating correction data for obtaining satellite orbital information by a mobile station, comprising:
a correction unit for calculating a correction between the first orbital data of the satellite and the second orbital data of the satellite, the second orbital data being more accurate than the first orbital data, the correction unit additionally representing the spatial components of the correction using a coordinate system having axes that move with the satellite moreover, the amendment is represented by one or more polynomials, and
a transmitter interface for transmitting corrections to the mobile station to enable the mobile station to estimate more accurate orbital data for the satellite by applying the correction to the first satellite orbital data stored in the mobile station. 42. The server system according to paragraph 41, further comprising:
an approximating unit for approximating a correction in a coordinate system in order to reduce the number of bits required for transmission to a mobile station. 43. The server system according to paragraph 41, in which the polynomials are one or more Hermite polynomials or Legendre polynomials. 44. The server system of claim 42, wherein the approximating unit uses coefficients of one or more polynomials to approximate the correction. 45. The server system according to § 42, where the server system is associated with a storage device for data to save an approximate correction for use by a mobile station. 46. The server system according to paragraph 42, further comprising:
a transmitting unit for transmitting the approximated correction to the mobile station over the network. 47. The server system of claim 42, further comprising:
a transmitter interface for broadcasting the approximated correction to one or more receiving devices, including a mobile station. 48. The server system according to paragraph 41, in which the coordinate system contains a radial axis parallel to the line or coinciding with the line that connects the starting point with the estimated position of the satellite. 49. The server system according to paragraph 41, in which the correction unit contains a logical node for calculating the clock correction for the satellite. 50. The server system of claim 49, wherein the clock correction is approximated by one or more coefficients of a series of one or more mathematical functions. 51. The server system according to paragraph 41, further comprising:
a receiver interface for receiving a reference time from a time server; and
a transmitter interface for transmitting a reference time together with an estimate of satellite positions to a mobile station. 52. A machine-readable medium having instructions stored on it executed by a processor on a server for:
calculating corrections between the first orbital data of the satellite and the second orbital data of the satellite, the second orbital data being more accurate than the first orbital data; and
transforming the spatial components of the correction from the first coordinate system to the second coordinate system so that the correction in the second coordinate system has a substantially smooth change over time, and
controlling the server transmitter interface to transmit the correction encoded in the second coordinate system from the server to the mobile station to enable the mobile station to estimate more accurate orbital data for the satellite by applying the correction to the first satellite orbital data stored in the mobile station, the correction in the second coordinate system represented by one or more polynomials. 53. The computer-readable medium of claim 52, further comprising instructions executed by the processor to interpolate the correction in the second coordinate system using one or more truncated polynomials to reduce the number of bits required for transmission to the mobile station. 54. The computer-readable medium of claim 52, wherein the second coordinate system comprises a radial axis parallel to a line or coinciding with a line that connects the starting point with the estimated position of the satellite, and the axis of the transverse track perpendicular to the radial axis and direction of movement of the satellite. 55. The computer-readable medium of claim 52, further comprising instructions executed by the processor to approximate the correction with a larger number of coefficients in at least one spatial dimension than other spatial dimensions. 56. The computer-readable medium of claim 55, further comprising instructions executed by the processor for:
approximating corrections with more coefficients in at least one spatial dimension than another spatial change, at least in part by presenting the correction using the coefficients of one or more polynomials as an approximated correction. 57. The computer-readable medium of claim 56, wherein the polynomials are one or more Hermite polynomials or Legendre polynomials. 58. The computer-readable medium of claim 52, further comprising instructions executed by the processor to calculate a clock correction for the satellite. 59. The computer-readable medium of claim 52, further comprising instructions executed by a processor to control a receiver interface to obtain a reference time from a time server; and controlling a transmitter interface for transmitting a reference time together with a rough estimate of satellite positions to a mobile station. 60. A mobile station for determining satellite orbital information, comprising:
a receiver interface for receiving input from a location server;
an evaluation unit for calculating correction data for the first satellite orbital data based on input from a location server, the correction data being one or more polynomials;
a conversion unit for converting the correction data represented by one or more polynomials from the first coordinate system to the second coordinate system, wherein the first coordinate system is selected to smoothly change the correction data over time; and
a recovery unit for applying correction data to the first orbital data to evaluate more accurate satellite orbital information. 61. The mobile station of claim 60, wherein the axes of the first coordinate system include a radial axis, wherein the radial axis is parallel or coincident with a line that connects the starting point with the estimated satellite position. 62. The mobile station of claim 60, wherein the reconstructing unit generates substantially corrected orbital data to estimate a satellite’s position and timestamp. 63. The mobile station of claim 60, wherein the input from the location server contains one or more coefficients of one or more polynomials for at least one axis of the coordinate system. 64. The mobile station of claim 60, wherein the polynomials are one or more Hermite polynomials or Legendre polynomials. 65. The mobile station of claim 63, wherein the estimating unit comprises a logic node for evaluating one or more polynomials using one or more coefficients and applicability time to obtain correction data. 66. The mobile station of claim 60, wherein the receiver interface receives input from a location server by transmitting a file from the data storage device. 67. The mobile station of claim 60, wherein the receiver interface receives input by receiving a message transmitted from the server. 68. The mobile station of claim 60, wherein the correction data is presented in the first coordinate system with higher accuracy in one spatial dimension than in other spatial dimensions. 69. A machine-readable medium having instructions stored on it executed by a processor on a mobile station for:
transforming the satellite orbital correction data represented by one or more polynomials from the first coordinate system to the second coordinate system, with the first coordinate system selected to smoothly change the correction data over time; and
applying correction data to the first satellite orbital data to estimate more accurate satellite orbital information. 70. The computer-readable medium of claim 69, further comprising instructions executed by the processor to determine a satellite’s position and timestamp based on the correction data. 71. The computer-readable medium of claim 69, wherein the first coordinate system includes a radial axis parallel to or coinciding with a line that connects the starting point with the estimated position of the satellite, and the axis of the transverse track perpendicular to the radial axis and direction of movement of the satellite. 72. The computer-readable medium of claim 69, wherein the correction data is presented in the first coordinate system with higher accuracy in one spatial dimension than in other spatial dimensions. 73. The computer-readable medium of claim 69, further comprising instructions executed by a processor to receive one or more polynomial coefficients for at least one axis of the coordinate system; and evaluating one or more polynomials using one or more coefficients and time of applicability. 74. The computer-readable medium of claim 73, wherein the polynomials are one or more Hermite polynomials or Legendre polynomials.

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