KR20080033287A - Method and apparatus for determining a location associated with an image - Google Patents

Abstract

The adverse effects of various sources of error present in satellite imaging when determining ground location information are reduced to provide more accurate ground location information for imagery, thereby rendering the information more useful for various entities utilizing the images. The determination of ground location coordinates associated with one or more pixels/sub-pixels of an image acquired by an imaging system includes obtaining a reference image, obtaining a target image associated with an earth view and the target image does not overlap the reference image. Known location information associated with the reference image is used to determine location information associated with the target image.

Description

METHOD AND APPARATUS FOR DETERMINING A LOCATION ASSOCIATED WITH AN IMAGE}

The present invention relates to the determination of ground coordinates associated with an image, and more particularly to the interpretation of compensated coordinate information from one or more images generated by an imaging system to other images.

Today, remote sensing systems of satellite and airborne applications generally provide images that can be processed to include the rows of pixels that make up the image frame. For many applications, it is desirable to recognize the ground position of one or more pixels in an image. For example, it may be necessary to have the ground position of an image pixel, expressed in geographic terms such as longitude, latitude, altitude. Many existing methods are used to represent the exact ground position of a point. In general, reference projections, such as the Universal Transverse Mercator (UTM), are known as US Geodetic Reference Network 27 (NAD27: North American Datum of 1927), US Geodetic Reference Network 83 (NAD83: North American Datum of 1983) and the World Geodetic System of 1984 (WGS84) along various horizontal and vertical datums. In addition, for images in the United States, pixels within the image may be obtained through a public land survey system (PLSS), such as a township / range / section of a particular state or county. Or it may be necessary to express the position of the object.

In order to obtain accurate ground position information of the image collected by the remote sensing system and to express it by the above-mentioned standard or other standards, the state of the imaging system at the time of image acquisition must be known to a certain degree. There are a number of variables that make up the state of the imaging system, which determines the precise area imaged by the imaging system. For example, in satellite imaging applications, various other factors include the orbital position of the satellite, the attitude of the imaging system, the atmospheric effects and thermal distortion of the satellite or its imaging system. Etc. all contribute to the accuracy with which the area to be imaged by the imaging system can be determined. Errors in recognizing each of these factors cause inaccuracies in determining the ground position of the areas imaged by the imaging system.

Although the present invention is not all of the factors, many factors used to generate ground position information for raw image data collected by a remote sensing platform may result in inaccurate ground position information for the associated image. It was recognized that it was affected by the errors that led to the derivation.

The present invention reduces the adverse effect of at least one error cause and derives more accurate ground position information for the image, making the information more useful for the various entities using the image. As a result, if a related entity has received a single ground image, the location of the various terrains within that ground image will be identified with improved accuracy, thereby improving the ability to use such images for a wider variety of applications. Improve.

One embodiment of the present invention provides a method of determining ground position coordinates for pixels in a satellite image. The method comprises the steps of (a) obtaining at least one reference image; (b) locating at least one first pixel in the at least one reference image, wherein the first pixel corresponds to a point having known global position coordinates; (c) determining a pixel position of the predicted point in the first image using at least one attitude, position and distortion information available for the satellite; (d) calculating at least one compensation factor based on a result of comparing the predicted pixel position of the point with a known position of the first pixel; (e) obtaining at least one target image by earth view, wherein the at least one target image does not overlap with the at least one reference image; and (f) Determining earth position coordinates for at least one pixel in the at least one target image using the compensation factor along with the flight attitude, position and distortion information available for the satellite.

The compensation factor is calculated by solving one set of equations related to platform position, attitude, distortion and ground position information for one image, so that adjustments for one or more positions, attitudes and distortions are obtained. Position, posture, distortion, and ground position information is known to change levels of accuracy in preference to adjustments. In addition, to obtain their adjustments related to the accuracy levels of each of the positions, attitudes, and distortions prior to adjustment, one set of equations, together with the preceding accuracy uncertainties in the form of covariance matrices, is solved. Can be augmented. Then, the adjusted posture, adjusted position, adjusted distortion information or any combination thereof is used as a compensation factor when determining the position coordinates for the target image. The target image may be collected before or after the collection of the reference image by the imaging system.

Another embodiment of the present invention provides a method for determining location information of a terrestrial image obtained from a remote detection platform. The method includes (a) acquiring at least one reference image; (b) obtaining at least one target image associated with one earth observation, wherein the at least one target image does not overlap with the at least one reference image; and (c) the at least one target image Using known location information associated with the at least one reference image to determine location information associated with the at least one reference image.

Yet another embodiment of the present invention provides an image of a terrestrial area that includes both a plurality of pixels and at least one ground position coordinate of the pixels. The pixels and coordinates are (a) acquiring at least one reference image, wherein the reference image comprises a plurality of pixels; (b) locating at least one first pixel within the at least one reference image associated with a point, wherein the point has a known global position coordinate; (c) calculating a compensation factor based on a result of comparison with the predicted pixel position of the point in the at least one reference image and the known position of the first pixel in the at least one first reference image; (d) obtaining at least one target image by earth observation, wherein the at least one target image comprises a plurality of pixels, wherein the at least one target image does not overlap with the at least one reference image And (e) determining global position coordinates for at least one pixel of the at least one target image based on the compensation factor.

Yet another embodiment provides a method of transmitting one image to one related entity via a communication network. The method includes transmitting a digital image comprising a plurality of pixels over a portion of the communication network, wherein at least one of the pixels is based on at least one ground point obtained from at least one reference image. And the ground position information derived based on the determined compensation factor, in which the at least one reference image differs from the digital image and does not overlap with each other.

1 is a diagram showing a satellite on Earth orbit to acquire the image of the ground,

2 is a block diagram showing a satellite shown in an embodiment of the present invention,

3 is a flowchart illustrating a performing step of determining position coordinates associated with an image of a satellite in an embodiment of the present invention;

4 is a diagram showing a reference image including points at which an exact position is known,

5 is a diagram illustrating a path including several imaged regions in one embodiment of the invention.

In general, the present invention relates to the determination of ground position information associated with at least one image pixel, obtained by an imaging system mounted on a satellite or other remote detection platform. The process of generating ground position information includes (a) acquiring one or more images (reference images) of areas containing points whose location is known precisely, (b) over time, available to the imaging system. Predicting the location of the points using varying position, flight attitude and distortion information; (c) using a data fitting algorithm to derive one or more compensation factors; Comparing the predicted positions, (d) interpolating or extrapolating the compensation factor (s) at different moments of time, and then (e) determining the exact known positions of the reference images. The compensation factor for one or more other images (target images) of areas that do not contain points having Applying (s). This process can be applied to a target image that does not overlap with the reference image.

The process of generating the image and ground position information is outlined, but one embodiment thereof is described in more detail. Referring to FIG. 1, a satellite 100 orbiting the earth 104 is shown. Initially, when referring to the earth herein, the reference may be made to any object that is desirable to obtain an image or other remote detection information that has an associated location associated with the planetary body. In addition, when referring to satellites herein, reference may be made to any spacecraft, satellite, aircraft or other remote detection platform with the ability to acquire images. It is also noted that none of the figures drawn here are drawn to scale, and such drawings are drawn for illustrative purposes only.

As shown in FIG. 1, the satellite 100 orbits the earth 104 along an orbit path 108. The position of the satellite 100 along the orbit path 108 may include several variables, including an in-track location, a cross-track location and a radial distance location. It can be defined as. The internal path location is relative to the position of the satellite along the orbit path 108 as the satellite orbits the Earth 104 orbit. The transverse path position is associated with the side position of the satellite 100 in relation to the direction of motion within the orbit 108. The radiation distance location is related to the radiation distance from the earth 104 to the satellite 100 (in relation to FIG. 1, this will be inside and outside of the page). These factors related to the physical position of the satellite are collectively referred to as the ephemeris of the satellite. When referring to the "position" of the satellite, reference is made to these factors. Also, with respect to the orbital path, the satellite 100 may have orientation values of pitch, yaw and roll, collectively referred to as its attitude. The imaging system mounted on the satellite 100 is capable of acquiring an image 112 that includes a portion of the earth 104 surface. Image 112 consists of a plurality of pixels.

When satellite 100 acquires an image of the earth 104 surface, based on information related to its state, including position, pose and distortion information of the imaging system, the associated ground position of any particular image pixel (s) is determined. It can be calculated, which will be described in more detail below. The ground position may be calculated in terms of latitude, longitude and altitude, or other applicable coordinate system. It is often desirable to recognize the location of one or more terrain associated with an image obtained from such satellites, and it is often desirable to also recognize the relatively accurate positional information of each image pixel. Images collected via the satellite can be used in commercial and non-commercial applications. The number of applications in which the image 112 can be usefully increased in imaging systems with higher resolution, and increased further when the ground position of one or more pixels included in the image 112 is known more accurately.

2, a block diagram depicting an imaging satellite 100 shown in one embodiment of the present invention is depicted. The imaging satellite 100 includes a position surveying system 116, a posture surveying system 120, a thermal surveying system 124, a transmit / receive circuit 128, a satellite motion system 132, a power supply system 136, and the like. Many instruments are included, including imaging system 140. Position surveying system 116 of the present embodiment includes a GPS receiver that receives position information from multiple Global Positioning System (GPS) satellites, which are well known in the art. Position surveying system 116 obtains information from the GPS satellites at periodic intervals. If it is desired that the position of the satellite 100 be determined in time between the periodic intervals, the GPS information from the position surveying system is generated by the satellite in order to generate the position of the satellite for a particular point within that time. It is combined with other information related to its orbit. As is typical of such a system, the position of the satellite 100 obtained by the position surveying system 116 includes a certain amount of error due to the limitations of the position surveying system 116 and the associated GPS satellites. In one embodiment, using data derived and purified from position survey system 116 data, the position of satellite 100 is known to be within a few meters. This error, although small, often contributes significantly to the uncertainty of ground position associated with the pixels of the ground image.

Posture measurement system 120 is used to determine posture information for imaging system 140. In one embodiment, posture measurement system 120 includes one or more gyroscopes for measuring angles and one or more star trackers for obtaining images of various objects. The positions of the various objects in the image obtained by the star tracker are used to determine the pose of the imaging system 140. In one embodiment, the star tracker is arranged to provide direction information of the roll, pitch, and yaw angle for a reference coordinate system fixed to the imaging system 140. Similar to that described above for the position survey system 116, the star tracker of the attitude survey system operates at periodic intervals to acquire an image. The attitude of the imaging system 140 can and often varies between these periodic intervals. For example, in one embodiment, the star tracker collects images at a rate of about 10 Hz, although the frequency may be increased or decreased. In this embodiment, the imaging system 140 operates to acquire an image at a line rate between 7 kHz and 24 kHz, although the frequencies may also be increased or decreased. In either case, the imaging system 140 generally operates at a higher speed than the star tracker, so that a plurality of terrestrial image pixels are obtained between the star tracker and the continuous attitude instrument. The attitude of the imaging system 140 with respect to the time interval between successive images of the star tracker is determined by using the star tracker's information along with additional information such as angular rate information from the gyroscope. Is determined for the purpose of predicting the posture. The gyroscope is used to detect the angular velocity of the imaging system 140 and, together with this information, is used to adjust posture information for the imaging system 140. Posture surveying system 120 also introduces errors in the predicted posture of imaging system 140 due to limitations on the accuracy of the information provided. These errors are generally small, but often contribute relatively significantly to the uncertainty of ground position associated with pixels in the ground image.

Thermal survey system 124 is used to determine the thermal characteristics of imaging system 140. In this embodiment, the thermal characteristics are used to compensate for thermal distortions in the imaging system 140. As is well known, the source of error in determining ground position relative to the image collected by such satellite based imaging system 140 is distortion in the imaging system. Thermal changes monitored by thermal survey system 124 are used in this embodiment to compensate for distortion in imaging system 140. For example, such thermal changes occur when satellites 100 or portions of satellites move in and out of sunlight due to shadows cast by the earth or other portions of the satellites 100. The difference in energy received at the components of the imaging system 140 results in the components being heated, thus distorting the imaging system 140 and / or the imaging system 140 and the position 116. And a change in alignment between the posture measurement system 120. For example, such energy changes can occur when the solar plate of satellite 100 changes orientation with respect to the satellite body, such that the components of the imaging system are subject to additional radiation from the sun. Reflections from the component parts of satellite 100 and satellite 100 moving in and out of the shadow of the earth, as well as energy reflected from the earth itself, can cause thermal changes in imaging system 140. For example, if a portion of the earth that reflects light to imaging system 140 is particularly cloudy, more energy is received in satellite 100 compared to the energy received in non-cloudy areas, resulting in additional Thermal distortion appears. Thermal survey system 124 monitors changing thermal characteristics, and this information is used to compensate for such thermal distortion. Thermal survey system 124 introduces errors in thermal compensation of imaging system 140 of satellite 100 due to limitations on the accuracy of the information provided. Although these errors are generally small, they also contribute to the uncertainty of ground position search when used to determine the ground position of pixels in an image that includes a portion of the earth's surface.

In addition to thermal distortion from imaging system 140, atmospheric distortion is also present which increases the error of imaging system 140. Such atmospheric distortion can be caused by various causes in the atmosphere associated with the area being imaged, including, for example, heating, water vapor, contaminants and concentrations of relatively high or low aerosols. Image distortion caused by such atmospheric distortion becomes a further component of error when determining ground position information related to the area imaged by imaging system 140. In addition to errors in position, posture and distortion information, the speed of the satellite 100 results in relativistic distortion in the received information. In one embodiment, satellite 100 moves at a speed of about 7.5 kilometers per second. At this speed, although relatively small, there are nonetheless relativistic considerations, and in one embodiment the images collected by the satellite 100 are compensated to reflect such considerations. Although this compensation is performed with a relatively high level of accuracy, some errors exist due to relativistic changes. These errors are generally small, but often have a relatively serious impact on the uncertainty of ground position search associated with the pixels of the ground image.

Added errors in position surveying system 116, posture surveying system 120, thermal surveying system 124, atmospheric distortion and relativistic changes lead to ground position calculations with an uncertainty of about 20 meters in one embodiment. . Although this uncertainty is relatively small in a typical satellite imaging system, further reducing this uncertainty may increase the usefulness of the ground image for a larger number of users, and also allow the image to be used in a larger number of applications. It will be possible.

The transmit / receive circuit 128 of this embodiment includes well-known components for communication via satellite 100 and ground stations and / or other satellites. The satellite 100 generally receives indication information relating to the position control of the satellite 100, the imaging system 140, the pointing control of various transmit / receive antennas and / or solar panels. The satellite 100 displays image data along with the satellite information obtained from the position measuring system 116, the posture measuring system 120, the thermal measuring system 24, and other information used for monitoring and controlling the satellite system 100. In general, transmit.

The exercise system 132 includes a number of momentum devices and thrust devices. The momentum device is used to control the satellite 100 by providing inertial attitude control as is well known in the art. As is well known in the art, the satellite position is controlled by thrust devices mounted on the satellite and operated to position the satellite 100 at various orbital positions. The motion system can be used to change the position of the satellites, and to position the sun or move the antenna, atmospheric drag, solar radiation pressure, gravity gradient effects or other external or internal effects. It is used to compensate for various perturbations resulting from numerous environmental factors such as forces.

Satellite system 100 also includes a power system 136. The power system can be any power system used to generate satellite power. In one embodiment, the power system includes a solar panel (not shown) having a plurality of solar cells that operate to generate electricity from light received at the solar panel. The solar panel is connected to the rest of the power system, which includes a battery, a power regulator, a power supply and a solar panel redirection circuit. This solar panel redirection circuit operates to increase the power output from the solar panel by redirecting the solar panel relative to the satellite system 100 so as to align it properly with the sun.

As mentioned above, imaging system 140 is used to collect images that include all or a portion of the earth's surface or surface. Such images may contain natural or artificial features, including but not limited to buildings, roads, vehicles, geological landmarks, agricultural elements, ships or platforms. have. In one embodiment, imaging system 140 employs a pushbroom type imager that operates to collect lines of pixels at adjustable frequencies between 7 kHz and 24 kHz. Imaging system 140 may include a number of imagers that operate to collect images within different wavelength bands. In one embodiment, imaging system 140 includes imagers for red, green, blue and near infrared bands. Images collected in these bands can be combined with each other to produce a color image of visible light reflected from the imaged surface. Similarly, images from either region or combination of regions can be used to obtain various types of information related to the imaged surface, such as agricultural information, air quality information, and the like. Although only four bands of the image have been described above, other embodiments may collect data through the sensor in more or less bands. Also in other embodiments, location information may be derived from or may be derived from other sensor types, sensors using active or passive collection technology, combinations of sensor types, sensors with different acquisition modes, or data thereof. Data can be collected from any remote detection device for which location information can be applied. Examples of sensor types include, but are not limited to, infrared sensors, ultraviolet sensors, radar sensors, raydar sensors, and thermal band sensors. In addition, other embodiments may use this sensor type with active or passive acquisition techniques. For example, in one embodiment, radar images may be acquired using active, bi-static radar technology, and in another embodiment, passive, CCD imaging technology may be used. Infrared images can be collected. In one embodiment, imaging system 140 consists of a combination of sensor types, in which the associated directions of the sensor types are known or surveyed to a pre-calculated accuracy. In other embodiments, but not limited to spot scanners, whiskbroom imagers, body-mounted frame cameras, and one- or two-axis steering mirrors. Sensors with different acquisition modes are used, including frame cameras using axis or two axis steering mirrors. The sensor type, acquisition technique, combination of sensor types, and acquisition mode used in a given embodiment will depend on the application using that data. In one embodiment, imaging system 140 includes an imager comprised of an array of CCD pixels, where each pixel can achieve up to 2048 levels of brightness and then for each pixel in the image. Can be represented as 11 bits of data. In another embodiment, one zone of the imaging system 140 is used for image topography, such as reefs or other natural or man-made structures that exist above or below the ocean surface.

The controls recorded in the acquired image may have geopositional accuracy of one pixel or less, and the matching of those controls to the acquired image may also have sub-pixel accuracy. For example, when the image's pixel size is 0.6 meters wide and 0.6 meters high, with the pixel size projected on the ground, the control at ground level is 0.3 meters CE90 (90th-percentile circular error) horizontal accuracy and 0.3 meters LE90 (90th- It is known to have a vertical accuracy of percentile linear error. Such accuracy information can be derived from the accuracy of GPS (Global Positioning System) positioning at ground level. The ground position of the control can then be defined by an individual "control chip" image of the adjoining area that surrounds the control, and the control chip itself is 0.6 meters wide by 0.6 meters high. It is a small image composed of possible pixels. The defined position of the control on the control chip image can be defined at the subpixel level, so that the accuracy of the placement of the control feature on the control chip will be at the subpixel level. The control chip is then written (matched) to the acquired image using common characteristic information in the chip's overlap to the acquired image. Over the entire common area, the matcher's ability to contrast the control chip and the acquired image with each other makes the matching accuracy smaller than the pixel size of the acquired image. With matching of the acquired image for that chip at the subpixel accuracy level, the placement accuracy of the control characteristics at the subpixel accuracy level, the accuracy of the ground control at the subpixel accuracy level, the resulting control records for the image Accuracy can be at the subpixel level. The compensation factor derived from this recording can thus be the subpixel level, and the error level of the successively acquired target image will be the subpixel level for a predetermined time determined before and after the capture of the reference image.

Referring to FIG. 3, operational steps used in determining terrestrial position information of an area imaged by a satellite system are described as an embodiment of the present invention. In one embodiment, the satellite collects multiple images along its orbital path. At the same time, information is continuously collected at predetermined intervals from the position surveying system, the posture surveying system and the thermal surveying system. These images are transmitted along the position, attitude and thermal information through one or more ground stations to an image generation system where the image and its associated position, pose and distortion information are processed along with any other known information related to the satellite system. . The processing can occur at any time and is processed in near real time. In this embodiment, the image includes both the reference image and the target image. As mentioned previously, the reference image is an image that overlaps one or more ground positions with known position coordinates up to a high level of accuracy, and the target image is one or more ground positions with known position coordinates up to a high level of accuracy. The image does not overlap with. In the embodiment of FIG. 3, the position of the satellite is determined with respect to the first reference image as shown in block 200. As mentioned above, the position includes information relating to the orbital position of the satellite at the time the first reference image was collected, and also includes in-track location, cross-track location. And a radial distance location. The position can be determined using information from the position surveying system and other terrestrial information used to improve the position information as a whole. At block 204, attitude information about the imaging system is determined. As discussed above, the pose of the imaging system includes the direction of the pitch, roll, and yaw of the imaging system relative to the orbital path of the reference coordinate system of the imaging system. When determining attitude information, information is collected from various components of the attitude survey system. This information is analyzed to determine the pose of the imaging system. At block 208, distortion information for the imaging system is determined. As monitored by the thermal survey system, the distortion information includes known changes in the optical components of the imaging system along with changes in the thermal distortion of the optical components. Distortion from the Earth's atmosphere is also included in the distortion information.

After the determination of the position, attitude and distortion information, the predicted pixel position of the at least one predetermined ground point is calculated according to block 212. In one embodiment, this predicted pixel position is determined using the position, attitude, and distortion information of the imaging system to calculate the ground position of at least one pixel in the image. More specifically, the position gives the position of the imaging system on the earth's surface, the posture gives the direction in which the imaging system is collecting the image, and the distortion is the state of the ray if there were no thermal, atmospheric or relativistic effects. How much distortion is given in. Along with the direction in which the imaging system is pointed, the position of the imaging system and the effects of distortion on the imaging system are represented by the theoretical positions on the Earth representation that produce light received by the imaging system. This theoretical position is then further adjusted based on the surface topography of the location on the earth's surface, such as in mountainous areas. This additional calculation is made and a predicted pixel position is produced.

As indicated by block 216, in accordance with the determination of the predicted pixel position of each predetermined ground point in the reference image, the predicted pixel position of each predetermined ground point in the reference image and the actual pixel of each predetermined ground point. Based on the comparison with the position, a compensation factor is calculated for one or more position, pose and distortion information. The calculation of the compensation factor (s) will be described in more detail below.

In accordance with the calculation of the compensation factor (s), using the compensated pose, position and / or distortion information, the ground position of at least one pixel in another image collected by the imaging system is calculated. In the embodiment of Figure 3, the compensation factor (s) is used if the positional accuracy of the pixels in the target image is higher than the accuracy achievable using other existing methods. As discussed above, satellites have various perturbations and temperature fluctuations over all orbits. Thus, at some point when the compensation factor (s) is calculated based on the difference between the predicted pixel position of the predetermined ground point in the reference image and the actual pixel position of the predetermined ground point in the reference image, the point is derived from the standard sensor. Until the ground position of the pixel predicted using sensor-derived surveying is more accurate than the ground position determined using the compensation factor (s), more changes in position, posture or distortion of the imaging system will result in the compensation factor ( S) will reduce the accuracy. In such a case, the compensation factor (s) may not be used, and the ground position of the pixel predicted using the survey derived from the standard sensor will be used for the ground position information. As mentioned at block 220, the ground position of one or more pixels in the second image is determined using the compensation factor (s). In this way, the ground position of the acquired image before and / or after acquiring the reference image can be determined with a relatively high level of accuracy. Also, if various reference images were acquired during the trajectory during image acquisition, it may be possible to determine the ground position of all the images acquired for that trajectory using the adjustment factors generated through each reference image.

Note that the order of operational steps described with respect to FIG. 3 can be modified. For example, the second image may be acquired first before the reference image is obtained. Although the second image may be obtained before the acquisition of the reference image, the compensation factor may be applied to the second image. In another embodiment, various reference images are obtained and a fitting algorithm for the predicted position for each predetermined ground point in each image to derive a set of compensation factors for the various images obtained between acquisition of the reference image. (fitting algorithm) is applied. Such a fitting algorithm may be a least squares fit.

Referring now to FIG. 4, the determination of the compensation factor (s) for one embodiment of the present invention is described. As discussed previously, an imaging system mounted on an imaging satellite acquires a reference image 300 that overlaps with one or more predetermined ground points. The location on Earth of each predetermined ground point can be expressed as latitude, longitude, and altitude for any suitable reference, such as WGS84. Such predetermined ground point can be any identifiable natural or artificial terrain included in the Earth image with a known location. Examples of predetermined ground points include, but are not limited to, sidewalk corners, building corners, parking lot corners, coastal terrain, and verifiable terrain on islands. One consideration in the selection of predetermined ground points is that it is relatively easy to identify the image of the area that contains the predetermined ground points. Although the predetermined ground point can be any point visible to the computer system or human, it is often desirable to have a high level of contrast and a known position relative to the surrounding area within the image. In one embodiment, image registration is used to determine the amount of error that appears at the calculated location of the predetermined ground point. Such image recordings may be based on general terrain, line features, and / or area correlation. Region contrast based on image recording evaluates the area of pixels around a point and records the area in a similarly sized area within the control image. The control image was acquired by a remote imaging platform and has a real local location known to a high degree of accuracy. The amount of error between the predicted location for the area and the actual location of the area is used to determine the compensation factor. Terrain and line records identify and match more specific items in the image, such as the edge of a building or sidewalk. A group of pixels identifies its outline or outlines the terrain, and its grouping is compared to the same grouping in the control image. Although the above discussion deals with the recording performed in pixel space, the same recording can be made with a predetermined accuracy in any other domain in which the transformation from pixel domain to that domain or from domain to pixel domain can be performed. Can be. For example, line terrain recording can be made in vector space by representing the terrain in the reference image as a vector and recording it to a vector known for the terrain in the control image. Similarly, local contrast recording can be made by representing a region in the reference image as a polygon and recording the polygon to a known polygon in the control image. In one embodiment, in order to increase the likelihood that the predetermined ground point is visible when the reference image 300 is collected, the predetermined ground point is selected within the position where the likelihood of cloud cover is reduced.

Referring again to FIG. 4, the predicted pixel position of four predetermined ground points, shown as A, B, C, and D, is determined relative to the reference image 300. The positions of A, B, C, and D are predicted of A, B, C, D based on surface position information such as attitude, position, distortion information, and altitude relative to the Earth's position on the imaging satellite, as shown in FIG. Pixel position. The actual pixel position of the predetermined ground point, identified as A ', B', C ', and D', is known for a high level of "a priori" accuracy. The difference between the predicted pixel position and the actual pixel position is then used to determine the compensation factor. In one embodiment, the compensating factor is a modified imaging system pose. In another embodiment, the compensating factors are a modified imaging system posture and a modified imaging system position. In another embodiment, the compensating factors are a modified imaging system attitude and a modified imaging system position, and corrected distortion information. In other embodiments where one or more of the attitude, position and distortion of the imaging system are compensated for, one factor will receive more compensation than the other.

In one embodiment, the compensation factor is determined by solving a series of equations with variables related to the position of the imaging system, the attitude of the imaging system, the distortion of the imaging system, and the ground position of the image obtained by the imaging system. In one embodiment where the imaging system posture is compensated, the position of the imaging system determined at block 200 in FIG. 3 is assumed to be correct, and the distortion of the imaging system determined at block 208 of FIG. 3 is assumed to be correct, and from the reference image The ground position of the pixel corresponding to the predetermined ground point is set to the known position of the predetermined ground point identified in the reference image. The equation is then solved to determine the compensated pose of the imaging system. This compensated pose is then used to determine the ground position of the pixel in that other image within the other image.

In one embodiment, triangulation is used to calculate the compensated imaging system pose. In this embodiment, triangulation is performed using a state-space estimation approach. State-space methods for triangulation can use least square methods, which are "a priori" information, or Bayesian estimation, such as statistical or Kalman filters. Use In an embodiment using the basic least square method, the position and distortion are estimated to be accurate, and the ground position relative to the pixel in the reference image corresponding to the predetermined ground point is estimated to be correct. Posture is then solved for compensation factors and used as compensation factors.

While the position parameters described above are assumed to have accurate or small covariance values, other alternative values may also be used when determining compensated imaging system attitude information. The imaging system pose is selected in the embodiment described above because the imaging system pose is the first source of uncertainty in this embodiment. By reducing the first cause of uncertainty, the accuracy of ground positions relative to other images that do not overlap with ground control points is increased. In other embodiments where the imaging system posture is not the first cause of uncertainty, other parameters may be compensated for as appropriate.

In another embodiment, the compensation factor is determined using a least squares method using "a priori" information. In this embodiment, the imaging system position, attitude, distortion, and pixel location of the predetermined ground point are used to calculate the compensation factor along with "a priori" covariance information associated with each of these elements. In this embodiment, all factors can be compensated with the total amount of compensation for each parameter controlled by their respective covariance value. Covariance values are a measure of uncertainty and can be expressed as a covariance matrix. For example, a 3x3 covariance matrix may be used for the position of the imaging system along with the elements of that matrix corresponding to the internal path, transversal path, and radiation distance positions of the imaging system. The 3x3 matrix contains diagonal elements, which are the variances of the position errors for each axis of position information, and the off-diagonal elements between the position errors for each element. Correlation factors. Imaging system attitude information, distortion information, and other covariance matrices for predetermined ground point locations may be generated.

Using a least square method or Kalman filter with "a priori" covariance values, compensation for each parameter is made. In addition, covariance values associated with each parameter are also generated. Thus, for example, "a posteriori" covariance of improved posture is known using covariance associated with attitude corrections.

As discussed previously, in one embodiment various reference images are collected from a particular trajectory of the imaging system. In this embodiment, as shown in FIG. 5, various images are collected at the satellite ground approach swath 400. Included in the collected images are the first reference image 404 and the second reference image 408. Reference images 404 and 408 are collected from an area within the satellite ground access swath 400 that overlaps a predetermined ground point. The areas containing the actual predetermined ground point are represented by control images 406 and 410 indicated by the diagonal lines in Fig. 5. In the example shown in Fig. 5, the third image 412 and the fourth image 416 are also obtained. They do not overlap with any predetermined ground points. Images 412 and 416 are target images. In this embodiment, the actual position of the predetermined ground point included in the first reference image 404 is compared with the predicted position of the predetermined ground point included in the first reference image 404. The first compensation factor is determined based on the difference between the predicted predetermined ground point position and the actual predetermined ground point position.

Similarly, the actual position of the predetermined ground point included in the second reference image 408 is compared with the predicted position of the predetermined ground point included in the second reference image 408. The second compensation factor is determined based on the difference between the predicted predetermined ground point position and the actual predetermined ground point position. Next, a combination of the first compensation factor and the second compensation factor can be used to determine the ground position for one or more pixels of each of the target images 412, 416 as described above.

The satellite's imaging system can be controlled to acquire various images in any order. For example, the satellite may acquire a third image 412 and a fourth image 416, and then obtain a first image 404 and a second image 408. In one embodiment, the images are obtained in the following order. A first reference image 404 is obtained, then a third image 412 is obtained, then a fourth image 416 is obtained, and finally a second reference image 408 is obtained. In this example, the compensation factors for the third image 412 and the fourth image 416 are calculated according to a least squares fit of the first compensation factor and the second compensation factor. If the images were acquired in a different order, it would be easy to calculate the compensation factors for the third image 412 and the fourth image 416 using similar techniques within ordinary skill in the art. .

As mentioned above, in one embodiment two or more reference images are collected and the images are used to calculate the compensation factor. In this embodiment, triangulation (through the method described above) is performed independently for each image to determine the compensation factor for each. These compensation factors are then combined to use to determine ground positions associated with images collected at the determined ground positions without using a predetermined ground point. The compensation factors may be combined using methods such as, but not limited to, interpolation, polynomial fit, simple averaging, and covariance weighted averaging. Alternatively, one triangulation (using the same method described above) can be performed on all images at once, thereby allowing global adaptation of the entire span of the trajectory within the appropriate timeframe. A global compensation factor is obtained. This global compensation factor can be applied to any image without the use of predetermined ground points.

As mentioned previously, satellites transmit the collected images to at least one ground station on Earth. The ground station is located where a satellite can communicate with the ground station for a portion of the orbit. The image received at the ground station can be analyzed at the ground station to determine positional information for the pixels in the image, and is sent to the user or data center (hereinafter called the receiver) with this information. Alternatively, raw data received from the satellite at the ground station can be sent directly from the ground station to the recipient without any processing to determine ground position information associated with the image. The raw data, including information related to the position, attitude, and distortion of the imaging system, is continuously collected at predetermined intervals and surrounds the ground access swath 400. The raw data can then be analyzed to determine an image that includes predetermined ground points. Using a predetermined ground point in those images, the ground position for the pixels in other images can be calculated along with the other information described above. In one embodiment, the image (s) may be sent to the recipient via the Internet. In general, images are delivered in a compressed format. Once the image is received, the receiver can create an image of the earth's location along with the ground location information associated with that image. It is also possible to deliver the image to the receiver in other ways. For example, the image (s) may be recorded on a magnetic disk, CD, tape or other recording medium and mailed to the recipient. If necessary, the recording medium may also include the position, attitude and distortion information of the satellite. It is also possible to print a hard copy of the image and mail the hard copy to the recipient. The hard copy can also be faxed to the recipient or sent electronically.

While the present invention has been presented and described through particularly preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (20)

In the method of determining the position information of the earth image, Obtaining at least one reference image; Obtaining at least one target image associated with an earth view, wherein the at least one target image does not overlap with the at least one reference image; And Using known location information associated with the at least one reference image to determine location information associated with the at least one target image. Position information determination method of the earth image comprising a. The method of claim 1, And the at least one reference image is associated with at least one terrestrial feature or at least one celestial object on the earth. The method of claim 1, Wherein said at least one target image is associated with at least one natural terrain on the earth, artificial terrain on the at least one earth, or both. The method of claim 1, Determining location information associated with the at least one target image Determining known location information of at least one celestial object or at least one topographical feature imaged by the at least one reference image; To determine at least one compensation factor and at least one error measurement, wherein the at least one error measurement is associated with the at least one compensation factor for the at least one target image. Using known location information and imaging system motion information; And Using the at least one compensation factor to determine location information associated with the at least one target image when the magnitude of the at least one error survey is less than a predetermined error limit. Position information determination method of the earth image comprising a. The method of claim 4, wherein Wherein the predetermined error limit is associated with at least one attitude, position and distortion measurement information associated with an imaging system. A method of determining position information of an earth image obtained from an imaging system, Obtaining at least one reference image; Obtaining at least one target image associated with earth observation, wherein the at least one target image does not overlap with the at least one reference image; Locating a first ground point in the at least one reference image with known geolocation information; Determining an expected position of the first ground point in the at least one reference image using at least one of position, pose and distortion information associated with the imaging system; And Calculating at least one compensation factor based on a comparison between the expected location information and known location information of the first ground point; And Determining position information of the at least one target image based on the at least one compensation factor. Position information determination method of the earth image comprising a. The method of claim 6, And the at least one reference image is associated with at least one topographical feature or at least one celestial object. The method of claim 6, Wherein said at least one target image is associated with at least one natural terrain on the earth, artificial terrain on the at least one earth, or both. The method of claim 6, Computing the at least one compensation factor When the at least one reference image has been acquired by an imaging system, determining first position information of the imaging system; When the at least one reference image has been acquired by an imaging system, determining first attitude information of the imaging system; When the at least one reference image has been acquired by an imaging system, determining first distortion information of the imaging system; And At least one of the first position information, the first posture information, and the first distortion information based on a difference between the position of the first ground point in the at least one reference image and the expected position of the ground point. Solving for the at least one compensation factor for Position information determination method of the earth image comprising a. The method of claim 9, Determining the position information of the at least one target image When the at least one target image has been acquired by the imaging system, determining second position information of the imaging system, wherein the second position information is modified by the at least one compensation factor; When the at least one target image has been acquired by the imaging system, determining second attitude information of the imaging system, wherein the second position information is modified by the at least one compensation factor; When the at least one target image has been acquired by the imaging system, determining second distortion information of the imaging system, wherein the second position information is modified by the at least one compensation factor; And Determining location information for at least one location in the at least one target image Position information determination method of the earth image comprising a. The method of claim 6, Computing the at least one compensation factor When the at least one reference image has been acquired, determining first position information and associated covariance of the imaging system; When the at least one reference image has been acquired, determining first attitude information and associated covariance of the imaging system; When the at least one reference image has been acquired, determining first distortion information and associated covariance of the imaging system; The first position information, the first attitude information, and the first distortion information of the imaging system based on a difference between the position of the first ground point in the at least one reference image and the expected position of the ground point. Solving for the at least one compensation factor for each, And said compensation factors are weighted by their respective covariances. The method of claim 11, Determining the position information of the at least one target image When the at least one target image has been acquired by the imaging system, determining second position information of the imaging system, wherein the second position information is modified by the at least one compensation factor; When the at least one target image has been acquired by the imaging system, determining second attitude information of the imaging system, wherein the second attitude information is modified by the at least one compensation factor; When the at least one target image has been acquired by the imaging system, determining second distortion information of the imaging system, where the second distortion information is modified by the at least one compensation factor; And Determining location information for the at least one location in the at least one target image Position information determination method of the earth image comprising a. An image of the earth observation comprising a plurality of pixels and at least one earth position coordinate of the pixels, The plurality of pixels and earth position coordinates Obtaining at least one reference image, wherein the at least one reference image comprises a plurality of pixels; Determining a first pixel location of at least one first pixel in the at least one reference image associated with a first ground point having a known earth location; Calculating at least one compensation factor based on a comparison of the expected pixel position of the first ground point and the first pixel position; Obtaining a target image of at least one earth observation, wherein the at least one target image comprises a plurality of pixels and the at least one target image does not overlap with the at least one reference image; And Determining an earth position for at least one pixel of the at least one target image based on the at least one compensation factor Image of Earth observations, characterized in that obtained by. The method of claim 13, And wherein the earth position can find its position up to sub-pixel precision. The method of claim 13, And said ground point comprises natural or artificial terrain. The method of claim 13, Computing the at least one compensation factor When the at least one reference image has been acquired, determining first position information and associated covariance of an imaging system; When the at least one reference image has been acquired, determining first attitude information and associated covariance of an imaging system; When the at least one reference image has been acquired, determining first distortion information and associated covariance of an imaging system; Calculating an expected pixel position of the first ground point based on the first position information, the first attitude information and the first distortion information; Determining a difference between the expected pixel position and the first pixel position; And Solving at least one compensation factor for each of the position, attitude, and distortion of the imaging system based on the difference; And said compensation factor is weighted by their respective covariances. The method of claim 16, Determining the location of the earth When the at least one target image is obtained, determining second position information of the imaging system; Determining second attitude information of the imaging system when the at least one target image is obtained; When the at least one target image is obtained, determining second distortion information of the imaging system; Applying the compensation factor to at least one of the second position information, the second attitude information, and the second distortion information; And Determining an earth position for at least one pixel in the at least one target image Image of earth observation, characterized in that it comprises a. In a method for transmitting an image over a communication network to an interested entity, Delivering a digital image of an earth observation including a plurality of pixels through a portion of the communication network, wherein at least one of the pixels is at least one determined based on at least one ground point from at least one reference image Related to ground location information derived based on the compensation factor of And the at least one reference image is different from the digital image and the at least one reference image does not overlap with the digital image. The method of claim 18, And the digital image is associated with at least one of the natural terrain on the earth, one or both of the at least one artificial terrain on the earth. The method of claim 18, And the at least one reference image is associated with at least one of the topographical features of the earth or at least one celestial object.

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