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NLOS Correction/Exclusion for GNSS Measurement Using RAIM and City Building Models.

Hsu LT, Gu Y, Kamijo S - Sensors (Basel) (2015)

Bottom Line: The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange.Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal.According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan. qmohsu@kmj.iis.u-tokyo.ac.jp.

ABSTRACT
Currently, global navigation satellite system (GNSS) receivers can provide accurate and reliable positioning service in open-field areas. However, their performance in the downtown areas of cities is still affected by the multipath and none-line-of-sight (NLOS) receptions. This paper proposes a new positioning method using 3D building models and the receiver autonomous integrity monitoring (RAIM) satellite selection method to achieve satisfactory positioning performance in urban area. The 3D building model uses a ray-tracing technique to simulate the line-of-sight (LOS) and NLOS signal travel distance, which is well-known as pseudorange, between the satellite and receiver. The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange. The measurement of the satellite will be excluded if the simulated and raw pseudoranges are inconsistent. Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal. According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

No MeSH data available.


Illustration of the devastated effect caused by double reflected non-line-of-sight (NLOS).
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sensors-15-17329-f003: Illustration of the devastated effect caused by double reflected non-line-of-sight (NLOS).

Mentions: In the LOS case, simulated pseudoranges can be estimated as the distance of the direct path between the satellite and the assumed position. In the multipath and NLOS cases, the simulated pseudoranges can be estimated as the distance of the reflected path between the satellite and the candidate position via the building surface. Ideally, if the position of a candidate is located at the true position, the difference between the simulated and measured pseudoranges should be zero. In other words, the simulated and measured pseudoranges should be identical. Therefore, the likelihood of each valid candidate is evaluated based on the pseudorange difference between the pseudorange measurement and the simulated pseudorange simulated by 3D building models and ray tracing. Finally, the expectation of all the candidates is the estimated positioning of the proposed map method. The proposed method is able to find the optimum position through a dedicated optimization algorithm of the above assumptions and evaluations. The detail algorithm of the particle filter using 3D city building models can be found in [23,24,25]. However, this particle filter still suffers from the effect of multiple reflected NLOS in the process of generating simulated pseudorange. In the developed method, a double reflected NLOS signal is devastating because of the assumption of single reflection. In a deep urban canyon environment, namely high buildings located on both sides of a street, the single reflection assumption is not always correct. If a double reflected NLOS is received, the developed method will estimate the user location at wrong side of street due to single reflection limit as shown in Figure 3. The candidates become invalid in the correct side of the street due to the incorrect assumption. As a result, the developed method will estimate a fault positioning solution.


NLOS Correction/Exclusion for GNSS Measurement Using RAIM and City Building Models.

Hsu LT, Gu Y, Kamijo S - Sensors (Basel) (2015)

Illustration of the devastated effect caused by double reflected non-line-of-sight (NLOS).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541937&req=5

sensors-15-17329-f003: Illustration of the devastated effect caused by double reflected non-line-of-sight (NLOS).
Mentions: In the LOS case, simulated pseudoranges can be estimated as the distance of the direct path between the satellite and the assumed position. In the multipath and NLOS cases, the simulated pseudoranges can be estimated as the distance of the reflected path between the satellite and the candidate position via the building surface. Ideally, if the position of a candidate is located at the true position, the difference between the simulated and measured pseudoranges should be zero. In other words, the simulated and measured pseudoranges should be identical. Therefore, the likelihood of each valid candidate is evaluated based on the pseudorange difference between the pseudorange measurement and the simulated pseudorange simulated by 3D building models and ray tracing. Finally, the expectation of all the candidates is the estimated positioning of the proposed map method. The proposed method is able to find the optimum position through a dedicated optimization algorithm of the above assumptions and evaluations. The detail algorithm of the particle filter using 3D city building models can be found in [23,24,25]. However, this particle filter still suffers from the effect of multiple reflected NLOS in the process of generating simulated pseudorange. In the developed method, a double reflected NLOS signal is devastating because of the assumption of single reflection. In a deep urban canyon environment, namely high buildings located on both sides of a street, the single reflection assumption is not always correct. If a double reflected NLOS is received, the developed method will estimate the user location at wrong side of street due to single reflection limit as shown in Figure 3. The candidates become invalid in the correct side of the street due to the incorrect assumption. As a result, the developed method will estimate a fault positioning solution.

Bottom Line: The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange.Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal.According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan. qmohsu@kmj.iis.u-tokyo.ac.jp.

ABSTRACT
Currently, global navigation satellite system (GNSS) receivers can provide accurate and reliable positioning service in open-field areas. However, their performance in the downtown areas of cities is still affected by the multipath and none-line-of-sight (NLOS) receptions. This paper proposes a new positioning method using 3D building models and the receiver autonomous integrity monitoring (RAIM) satellite selection method to achieve satisfactory positioning performance in urban area. The 3D building model uses a ray-tracing technique to simulate the line-of-sight (LOS) and NLOS signal travel distance, which is well-known as pseudorange, between the satellite and receiver. The proposed RAIM fault detection and exclusion (FDE) is able to compare the similarity between the raw pseudorange measurement and the simulated pseudorange. The measurement of the satellite will be excluded if the simulated and raw pseudoranges are inconsistent. Because of the assumption of the single reflection in the ray-tracing technique, an inconsistent case indicates it is a double or multiple reflected NLOS signal. According to the experimental results, the RAIM satellite selection technique can reduce by about 8.4% and 36.2% the positioning solutions with large errors (solutions estimated on the wrong side of the road) for the 3D building model method in the middle and deep urban canyon environment, respectively.

No MeSH data available.