Abstract
Abstract Nowadays (November 2015) there are two global fully operational satellite navigation systems, American GPS and Russian GLONASS. Two next are under construction, Galileo in Europe and BeiDou in China. As the error of observer’s position obtained from these systems depends on geometry factor DOP (Dilution Of Precision) among other things the knowledge of the number of satellites visible by this observer above given masking elevation angle Hmin and the distributions of DOP coefficient values, GDOP in particular, is very important. The lowest and the greatest number of satellites visible in open area by the observer at different latitudes for different Hmin, the percentage of satellites visible above angle H (9 intervals, each 10O wide), distributions (in per cent) of satellites azimuths (8 intervals, each 45O wide) and GDOP coefficient values (8 intervals) for Hmin = 5O for all these four systems at different observer’s latitudes (9 intervals, each wide 10O wide) are presented in the paper. Additionally the lowest elevation for which the number of satellites visible at different latitudes by the observer in open area above this angle is equal 4 or 3 and the distributions (in per cent) of GDOP coefficient values for different Hmin at observer’s latitudes 50-60O for the same four systems are showed. All calculations were made for constellation of GPS 27 satellites, GLONASS 24, Galileo 30 and BeiDou 27 MEO satellites.
Highlights
The error M of the observer’s position obtained from satellite navigation system depends on geometry factor DOP (Dilution of Precision) among other things
Two satellite navigation systems (SNS) are under construction, Galileo in Europe and BeiDou in China (Chatre E, 2015), (China Satellite Navigation Summit, 2015)
The final BeiDou space constellation will consist of 35 satellites (27 MEO, 5 GEO, 3 IGSO) but as the signals transmitted by all GEO and IGSO satellites can be used in some regions of the Earth (China and adjacent areas) merely, the 27 MEO satellites were taken into account only (Munich 2015)
Summary
The error M of the observer’s position obtained from satellite navigation system depends on geometry factor DOP (Dilution of Precision) among other things. In order to compare BeiDou MEO and GPS (MEO ) constellations it was assumed that the number American system satellites is equal 27 too even though since several years this number is incessantly at least 29 or 30 (www.gps.gov), (www.gpsworld.com). The parameters of the spatial segment and coverage surface area ensured by one satellite only of all four mentioned above SNSs are presented in Table 1 (Januszewski J, 2010), (www.gps.gov), (www.insidegnss.com). In calculations it was assumed the radius of the Earth 6,370 km and the Earth’s surface 510,066,000 km. Because Galileo orbit altitude is the highest the coverage surface area is in the case of this system the greatest, near 40 % of the Earth
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