当前位置:网站首页>GPS from getting started to giving up (XI), differential GPS
GPS from getting started to giving up (XI), differential GPS
2022-07-06 22:03:00 【Chasing wind】
One 、 principle
Difference GPS By eliminating or reducing GPS The measurement error is thus improved GPS Method of positioning accuracy .
Difference GPS The basic principle of eliminating or reducing measurement errors is to use the correlation of errors . Take satellite clock error for example . If we know the actual exact position of a receiver , Subtract from its measured position , The error term can be obtained , This error term includes the satellite clock error . If another receiver also receives the same satellite signal nearby to locate , It can reduce the error term in the calculation , This eliminates the satellite clock error , Because for these two receivers , Their satellite clock error is the same , This is the correlation of errors .
Of course , For both receivers , Not all errors are the same , But within a certain range , There are still some errors that are similar . such as Ionospheric delay , If two receivers are close , It can be approximately regarded as the same ; Empathy , Tropospheric delay 、 This correlation also exists in satellite ephemeris . Other errors are multipath 、 The receiver noise is irrelevant , So such an error cannot pass the difference GPS To eliminate , contrary , They also cause the superposition of errors .
In this difference method , We call the receiver with known location as reference station or base station , Those whose location is unknown are called mobile stations , The error correction value is broadcast by the reference station , The mobile station uses the error correction value to correct the position .
From difference GPS The working principle of is easy to see , The closer the mobile station is to the base station , The correction effect will be better . We call the distance between the mobile station and the reference station Baseline distance , The length of Baseline length .
Two 、 classification
Classification by baseline distance : Local area 、 Area 、 wide area
- Local area is general 10km~100km.
- The wide area can cover the whole continent or the whole world .
- The area is between local area and wide area .
- The target parameters corrected by difference are different , Can be divided into : Position difference 、 Pseudo range difference 、 Carrier phase difference
- Position difference : The base station broadcasts the difference between the position calculated according to its own pseudo range observation value and the known self position , The mobile station calculates the position according to its pseudo range observation value, and then adds the received difference broadcast by the base station to get its final position . This method requires that the position coordinates calculated by the mobile station and the reference station respectively contain the same error term , It also requires that the mobile station and the reference station adopt the same positioning algorithm and the same set of satellite measurements , It's hard to achieve , Poor performance , So I don't use much .
- Pseudo range difference : What the base station broadcasts is the difference between its own pseudo range observation value and the known distance from itself to the satellite , The mobile station uses its own pseudo range observation value plus the received pseudo range difference broadcast by the base station to obtain its own final pseudo range , And then used for position calculation . This method does not require the mobile station and the reference station to adopt the same positioning algorithm , Its accuracy can reach decimeter level .
- Carrier phase difference : Similar to pseudo range difference , Only the base station broadcasts the carrier phase difference correction , There is no need to solve the integer ambiguity in the difference correction term , Just keep its value unchanged ; The mobile station still needs to solve the problem of weekly ambiguity . The accuracy of this method can reach the millimeter level at most .
According to the positioning results, it can be divided into : Absolute positioning 、 Relative positioning
- Absolute positioning requires knowing the precise position of the reference station .
- Relative positioning seeks the position of the mobile station relative to the base station , At this time, the absolute position of the base station may not be known , The base station can directly broadcast the observed values to the mobile station , Instead of broadcasting differential corrections .
Divide by difference : Single difference 、 Double difference 、 Three bad
Single difference : It is the difference between the measured values of two different receivers on the same satellite . It can eliminate the satellite clock error . In the case of a short baseline , It can also basically eliminate the atmospheric delay error . The error of satellite ephemeris is basically eliminated . But the mean square deviation of the measurement noise is expanded to the original root sign 2 times .
Double difference : The difference between the measured values of two satellites by two receivers at the same time , Equivalent to the difference between two single differences , It can eliminate the clock error of the receiver . This is because the receiver clock difference is the same for different satellites . The mean square deviation of double difference noise is single difference Radical sign 2 times .
Three bad : The difference between the measured values of two satellites by two receivers at two times , Equivalent to the difference between two double differences , Double difference cycle ambiguity can be eliminated . This is because when the receiver locks a satellite signal , It keeps the integer ambiguity in the carrier phase measurement of the satellite signal unchanged . Three difference noise mean square deviation is the root of double difference 2 times .
According to the movement state : Static positioning 、 Dynamic positioning
- Static positioning : The measured value can be collected continuously for a long time , And do post-test processing , To improve accuracy .
- Dynamic positioning : It usually meets the requirements of real-time .
According to the real-time requirements : real-time processing 、 Post test processing
3、 ... and 、 Further improvement measures
- The site selection of the reference station is generally open 、 The ground reflection is weak 、 Higher ground , And choose choke antenna and high-quality receiver , To suppress the multipath effect and its own error as much as possible .
- The reference station broadcasts the pseudo range correction value after deducting the influence of its own clock error , To avoid adding error to the user receiver .
- In addition to broadcasting pseudo range correction values, the reference station , The rate of change of the pseudo range correction value is also broadcast , To facilitate the use of the user receiver .
- Large baseline , The local ionosphere is used for the reference station and the mobile station respectively 、 Tropospheric model , It can improve the positioning accuracy .
- If a region is covered by multiple reference stations , The weighted average can be corrected separately , It can reduce the error , Improve accuracy .
- Wide area differential GPS The system is usually responsible for the error of satellite ephemeris 、 Satellite clock error 、 Ionospheric delay, etc. respectively provide differential correction .
边栏推荐
猜你喜欢
Xiaoman network model & http1-http2 & browser cache
uni-app App端半屏连续扫码
guava:Collections. The collection created by unmodifiablexxx is not immutable
Uni app app half screen continuous code scanning
GPS从入门到放弃(十五)、DCB差分码偏差
PostgreSQL 修改数据库用户的密码
PostgreSQL 安装gis插件 CREATE EXTENSION postgis_topology
基于LM317的可调直流电源
搜素专题(DFS )
GPS from getting started to giving up (XV), DCB differential code deviation
随机推荐
设置状态栏样式Demo
基于InsightFace的高精度人脸识别,可直接对标虹软
Numpy download and installation
GPS from getting started to giving up (16), satellite clock error and satellite ephemeris error
The underlying implementation of string
Sparkshuffle process and Mr shuffle process
Sequoia China, just raised $9billion
GPS從入門到放弃(十三)、接收機自主完好性監測(RAIM)
Earned value management EVM detailed explanation and application, example explanation
The relationship between root and coefficient of quadratic equation with one variable
hdu 4912 Paths on the tree(lca+馋)
Leveldb source code analysis series - main process
GPS from getting started to giving up (XV), DCB differential code deviation
Method return value considerations
数字化转型挂帅复产复工,线上线下全融合重建商业逻辑
GPS从入门到放弃(十一)、差分GPS
Powerful domestic API management tool
PostgreSQL modifies the password of the database user
MySQL removes duplicates according to two fields
华为在多个行业同时出击,吓人的技术让欧美企业瑟瑟发抖