DGPS (Differential GPS) positioning technique is widely used, especially in maritime applications. The DGPS reference station provides PRC (Pseudo-Range Corrections) to the user, and s/he corrects the received pseudo-range measurements with PRC. Positioning accuracies of DGPS are at the level of 1-3 meters.
When the user is far away from the base station, however, the quality of PRC information deteriorates due to the spatial decorrelation of GPS errors between the reference and user locations. To solve this problem, concept of network-based DGPS came along. By combining and interpolating PRC messages from multiple sites, the user can overcome the problem of spatial decorrelation.
DGNSS Server at PP-Solution
PP-Solution is operating 15 reference stations nationwide, and four of them are providing DGPS correction messages.
The map below shows 15 reference stations, of which 4 DGPS reference stations are starred. By utilizing “patented” DGPS algorithms, our DGPS server provides PRCs optimized for each user, or the user can implement our interpolation algorithm in their positioning device. Through this innovation, the user can achieve ~1 meter accuracy.
Another advantage of the DGNSS server at PP-Solution is that it provides GLONASS and Beidou PRC messages together with GPS ones. Thus, it is truly a DGNSS (Differential Global Navigation Satellite System) server. It means that you can improve your positioning accuracy in the mountainous area or on city streets where you cannot see many satellites due to signal blockage. As shown in the skyplot, one gets less than 10 GPS satellites at a given epoch in Asia while more than 20 satellites are visible when GLONASS and Beidou combined.
DGNSS vs DGPS
Not only the user sees more satellites with multiple satellite navigation systems (GNSS), but also get better accuracy. The green, purple, and mustard color dots in the figure below shows positioning accuracies of GPS, GLONASS, and Beidou, respectively. The black dots are for the combined, eg. GNSS positioning. The test results prove the fact of “The more satellites you see, you get better accuracy”. When differential GNSS corrections available through PP-Solutions’ DGNSS service are used, one can easily achieve sub-meter accuracy.