GPS World, March 2016
ALTERNATIVE PNT MARCH 2016 WWW GPSWORLD COM GPS WORLD 27 TABLE 2 DOP values for M N SOPs HDOP and GDOP Unmanned Aerial Vehicle The initial position of a receiver mounted on a UAV was set to r 106 r 2504728 465991 3551203 T The receivers true trajectory evolved according to velocity random walk dynamics Pseudorange observations on all available GPS SVs above an elevation mask set to el 20 and sv min three terrestrial SOPs were generated using a MATLAB based simulator The simulator used SV trajectories which were computed using GPS SV ephemeris files from Sept 1 2015 10 00 to 10 03 a m The positions of the SOPs were set to 106 2504953 4659550 r sop 1 3551292 T r sop 2 106 2503655 4659645 3552050 T and r sop 3 106 2504124 4660430 3550646 T which are the locations of surveyed cellular towers in the UAVs vicinity The UAVs true trajectory navigation solution from using only GPS SV pseudoranges and navigation solution from using GPS and SOP pseudoranges are illustrated in FIGURE 3 top The corresponding 95thpercentile uncertainty ellipsoids for a sample set of navigation solutions are illustrated in Figure 3 bottom The following can be noted from these plots First the accuracy of the vertical component of the GPS only navigation solution is worse than that of the GPS SOP navigation solution Second the uncertainty in the vertical component of the GPSonly navigation solution is larger than that of the GPS SOP navigation solution which is captured by the yellow and blue uncertainty ellipsoids respectively Third the accuracy of the horizontal component of the navigation solution is also improved by incorporating cel lular SOP pseudorange observations alongside M SVs N SOPs M N 4 0 4 1 4 2 4 3 5 0 5 1 5 2 5 3 VDOP 3773 1561 1261 1080 3330 1495 1241 1013 HDOP 2246 1823 1120 1073 1702 1381 1135 1007 GDOP 5393 2696 1933 1654 4564 2294 1880 1566
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