Presentation About GPS Technology

8/10/2019 Presentation About GPS Technology

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Presentation about GPS technolo

Fu zhou



Paper introduction

• Three significant papers describe the importance of signaltransmit ,integrity monitoring and radio frequency interfereGPS technology.

• Currently, the GPS technology not only focus on positioning object, also concentrated on the improvement of accuracy.

be clutters like FM radio and forest environment, GPS shoulof detecting the correct position to give the user the feedbaFurthermore, the map matching algorithm is the key procedimprove the performance of the map matching process.



GPS/GNSS survey in the fenvironment

Test surveys for the developed technology were carried out on a point forest, with a high degree of difficulty for satellite access. The coordina

point were determined by three GPS/GNSS receivers positioned in a lspecial base, which were separated by a fixed distance of 0.5 m. The te

were conducted using Topcon HiPer Pro receivers with 10-Hz RTK positgathering data at a sampling rate of 10 Hz.



paper uses a technology with three rover GPS/GLONASS receiveGNSS receivers are placed on an aluminum beam at set distanceeach other. The beam itself is mounted with a tribrach on the tripothe middle receiver is directly set over the measured point.



The program allows the recording and analyzing of positions frommeasurements from three receivers simultaneously.



The use of two navigation systems in positioning resulted in a substantiin the number of satellites evenly distributed in the sky. Despite the diffiobservational conditions, the number of satellites ranged between 17 anthe RTK survey and the raw GPS and GLONASS observation recordingrecording frequency of 0.1 s (10 Hz),were carried out during the wholemeasurement session.



Broad observational material was obtained this way for 54 000 poeach receiver. During the experiment, FIXED solutions (where theambiguities of phase measurements are calculated as integers) w8% –19% of all results, depending on the receiver. The vast majorwas as much as 81 –92%, were FLOAT solutions (i.e., the ambigunot integer numbers).



Conclusion

• The use of two navigation systems for the RTK positioning resultincreased reliability of the obtained solutions. Increasing the posfrequency caused an enhancement in the FIXED determinations.measurement under dense tree canopies caused four (out of 18)solutions to be obtained in the RTK positioning during the experpresented measurement technology allowed all gross errors to b

eliminated, and it considerably reduced systematic errors. The coof two measuring techniques resulted in obtaining reliable coordwith centimeter accuracy. Coordinates with centimeter accuracyobtained in 15 out of the 18 conducted 5-min sessions on a poina dense forest with completely obstructed access to satellites.



GPS Integrity Monitoring

• In this paper, a new technique for providing high integrity Ginformation for land vehicle monitoring systems is proposedproposed method provides a three level integrity check.



A receiver autonomous integrity monitoring (RAIM) algorithm is usemeasure the quality of GPS positioning output. GPS Doppler informused to check the integrity of vehicle velocity, which adds a new layintegrity and could improve the performance of the map matching pThe final level in the integrity check requires confirming the integritymap matching algorithm.



In the algorithm, a horizontal protection level HPL parameter is uscheck RAIM availability. After computing HPL based on data gaththe GPS, it is compared to the maximum horizontal alert limit (HA







Effect of Radio frequency interferenGPS

• study was conducted on single- and dual-frequency GPS recdifferential GPS (DGPS) mode via static observations. All thewere focused on in-band interference at the GPS L1 and L2 fbands with the interference signal power levels being increa-140 dB until the accuracy of GPS was affected. The use of dprecision (DOP) alone to quantify the quality of GPS was fou

insufficient, and hence, residual positions have been used tothis effect.



Kuala Klawang (KLAW) and Universiti Putra Malaysia (UPMS),Both data stations aGeodesy Section, Department of Surveying & Mapping Malaysia (DSMM), and bothrepresent two different types of GPS receivers (i.e., single and dual-frequency). Theat least 30 minutes of observation, minimum of five satellites must be in view, eleva

than 15 degrees, and at least 60% of sky coverage.



Data processing

The Leica Ski-Pro software was used to process the collected Information about epochs, ambiguity status, power levels, gedilution of precision (GDOPs) and 3D position was extracted uMatlab for graph distributions.



•The findings of this study have demonstrated the effects of single and dual-frequency GPS receivers. For absolute positiwith GPS, single frequency receivers will experience interferearlier than dual frequency receivers with the noise level at For relative positioning, dual frequency receivers outperformsingle frequency receivers where it can resist the effect of R

Since the RFI effect is frequency dependent, it can be virtuaminimized by differencing L1 and L2 phase measurements, ashort baseline (10km) produces better results than long bas(30km) whenever an observation is corrupted with RFI.

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Presentation About GPS Technology