JPH075239A - Gps receiver - Google Patents

Abstract

PURPOSE:To correct the degrading of position accuracy at a low cost without special equipment depending on selective utilizing property by extracting the diurnal component of changes in position from a data observed at a known fixed point to be stored together with time for use as correction value. CONSTITUTION:Signals received by an antenna 1 and a receiver 2 are demodulated to perform a position calculation with a arithmetic section 3. A satellite radiowave is received at a fixed known point for more than 24 hour and a difference between the fixed point positional information and a measured position obtained by receiving radiowaves to compute is determined to be supplied to a signal processing section 5. A position error data (diurnal component of positional changes) extracted with a processing section 5 is stored into a memory section 6 together with date and time data. When a receiver is used in a moving object such as ship later for position measurement, in computation with the arithmetic section 3, a memory data of the memory section 6 is used to determined a position by correction. As a satellite appears at the same position as that on the preceding day at a cycle of about 23 hour and 56 minute, it is advanced by 4 minute per day thereby enabling the correction of the data by the memory data four minute later back from the preceding day.

Description

Detailed Description of the Invention

[0001]

[Industrial application] In a GPS positioning system, selective usability (S
A) is being implemented. The present invention relates to a device that slightly corrects this deterioration in position accuracy.

[0002]

2. Description of the Related Art In a GPS positioning system, selective availability (SA) is implemented as a means for intentionally deteriorating its position accuracy, and this SA is corrected by differential GPS (DGPS). According to DGPS, not only the deterioration of the measurement position due to SA but also the ionospheric disturbance error can be corrected, which is epoch-making in terms of correction, but since SA with a short fluctuation cycle is also included, it is almost real-time. Correction data must be transmitted, and a dedicated receiver for correction data is required. Moreover, it cannot be used anywhere other than where the system was built.

[0003]

DGPS requires a communication means for transmitting correction data in real time.
Therefore, in order to make DGPS usable on land and coast all over the world, it takes a huge amount of cost to construct a positioning station and communication equipment, and therefore it can be used only in an area where some DGPS systems are constructed. Even in areas without the DGPS system, deterioration of location due to selective availability (SA)
There is a problem of wanting to make corrections at low cost without any special equipment.

[0004]

As means for degrading the position accuracy due to selective availability (SA), there are two means for operating orbit information of individual GPS satellites and means for operating clocks of individual GPS satellites. There are different types, and usually S due to their combination
A is being implemented. When observing SA, the position measured by the SA element that operates the clock of the GPS satellite fluctuates in a cycle of about 10 minutes, but it seems that there is no regularity. However, in the SA element that operates the satellite orbit information, the positioning position fluctuates in a long cycle of time unit, and has a periodicity of about 23 hours and 56 minutes.

Therefore, in SA, the position fluctuation value due to the orbital information element of the GPS satellite is observed and extracted at a known fixed point and stored as a correction value together with the time, and at the time of positioning after the next day, 4 times per day. By correcting the position with the stored correction value shifted at a later time by a minute, the position calculation is performed by correcting S due to the orbital element of the GPS satellite in the position accuracy deterioration due to SA.
A deterioration amount can be improved.

[0006]

[Example] FIG. 2 is a diagram in which the position variation during normal SA implementation is observed at a fixed point, and 6 hours of one day are recorded along with the time in the latitude and longitude directions. Similarly, FIG. 4 shows the data when only the satellite orbital elements of the SA are implemented and the SA is stopped by the operation of the satellite clock. 3 and 4 are about 23 hours 5
The position change is very similar in the period of 6 minutes, which indicates that position correction is possible only for the SA component of the satellite orbital element.

FIG. 1 shows the configuration of a GPS receiver according to the present invention. The GPS signal received by the antenna 1 and the GPS receiver 2 is demodulated, and the calculation unit 3 calculates the position. The GPS radio wave is received at a known fixed point for at least 24 hours or more, and the fixed point position information previously input from the fixed point position input unit and the G obtained by the calculation by receiving the GPS electric wave are calculated.
The difference from the PS measurement position, that is, the position error is calculated and supplied to the next signal processing unit 5.

The signal processing unit 5 removes a component having a short cycle of about 10 minutes from the fluctuation of the position error. As a method of removing a component having a short cycle, a method of obtaining an intermediate value between a maximum value and a minimum value of fluctuation values of a cycle of about 10 minutes and continuing the method,
It can be extracted by a method of removing with a long cycle filter.

The data from which the position error component having a short cycle of about 10 minutes is removed is given to the storage unit 6 and stored together with the date and time data output from the calculation unit 3. The storage amount is 24 hours, but the data storage interval may be about 1 minute.

When the GPS receiver shown in FIG. 1 is used and measured at a later date on a moving body such as a ship, the position is corrected by using the data stored in the storage unit 6 during the calculation by the calculation unit 3. At this time, the time of the stored data is corrected with respect to the measured time by the data shifted by about 4 minutes per day.
In other words, GPS satellites appear at the same position as the previous day in a cycle of approximately 23 hours and 56 minutes, so each day will advance by approximately 4 minutes,
On the contrary, the correction data is corrected by the stored data about 4 minutes after the previous day.

The data in the storage unit 6 can be obtained by measuring one's own GPS receiving device at a known fixed point, but the correction data obtained by another GPS receiving device is used for each GP.
It is also possible to receive and store from the external information input / output terminal 8 of the S receiver through transmission or via a floppy disk or the like.

Since the correction data is valid for several days or more or one month or more, the correction data can be collected for long-term averaging. In addition, it is not the position error variation of the measurement calculation result, but G
If the orbit information element of the GPS satellite is extracted from the error variation of each PS satellite, the amount of data increases, but there is an advantage that it can be used even if the combination of GPS satellites used for position calculation is different.

A specific correction data format and means stores the amount of deviation from a known fixed point, that is, the correction value data by dividing it into latitude and longitude as shown in FIGS. It is also possible to make corrections for each longitude, but it is also possible to make corrections by storing as data of distance and direction of deviation from a fixed point. Further, like the correction data of the DGPS, it is possible to select the correction data format and the correction means according to the necessity such as storing the deviation amount of the distance to each satellite and performing the position calculation after the correction.

[0014]

As described above, according to the present invention,
In SA, the position variation value due to the orbit information element of the GPS satellite is observed and extracted at a known fixed point and stored as a correction value together with the time, and at the time of positioning after the next day, 4 per day
GPS is included in the position accuracy deterioration due to SA by correcting the position with the memory correction value shifted at a later time
It is possible to improve the SA deterioration caused by the orbital elements of the satellite. Further, it can be realized if there is a GPS receiver of its own or one GPS receiver separately, and it is possible to realize it in any area without the need to build a special system. Furthermore, the signal processing unit 5 and the storage unit 6 can be built in the GPS receiver and realized at low cost.

[Brief description of drawings]

FIG. 1 is an embodiment of the present invention and shows a configuration related to the present invention of a GPS receiver.

FIG. 2 is an example of observation showing a variation state of deterioration of position accuracy due to GPS availability (SA).

[Fig. 3] Observation example when only the satellite clock operation is canceled and only the satellite orbit information is operated, out of the GPS availability (SA)

[Fig. 4] Similar to Fig. 3, an example of observation on the next day (after 23 hours and 56 minutes)

[Explanation of symbols]

 1 antenna 2 GPS receiver 3 arithmetic unit 4 fixed point position input 5 signal processing unit 6 storage unit 7 time input terminal 8 external information input output terminal

Claims (3)

[Claims] 1. A storage unit for extracting a daily cycle component of position variation from GPS data observed at a known fixed point and storing it together with time, and a position calculation of the daily cycle component and time of position variation stored in the storage unit. A GPS receiving device comprising: a correction unit that sets a time correction value. 2. Storage means for extracting a daily cycle component of position variation from GPS data observed at a known fixed point and storing it together with time, and reading for reading out the daily cycle component of position variation and time stored in the storage means. A GPS receiving apparatus comprising: a means for correcting the position variation, and a correction means for using the time period component of the position variation stored in the storage means read by the reading means as a correction value for position calculation. 3. Storage means for extracting the diurnal cycle component of the position variation, which is observed and stored at the known fixed point, from the variation data of the distance for each GPS satellite and storing it together with the time, and for each individual satellite. The GPS receiving apparatus according to claim 1 or 2, further comprising: a correcting unit that calculates a position and corrects the distance after correcting the distance.