GPS World, June 2017
SENSOR FUSION or not The real differentiator in the land profile is the attitude performance due to the use of phase windup as a constraint Moreover the attitude improvements are certainly tied to IMU quality UUT1 exhibited a noticeable improvement in the att itude performance while the higher performance IMUs did not This is not entirely unexpected as the precision of the phase windup is lower than that of the higher grade IMUs Looking at the data graphically FIGURE 7 shows the effect of land profile on positioning performance in this scenario The two solutions are indistinguishable on the plot and are all within standard RTK level error bounds as was indicated in the RMS table Figure 7 shows the attitude accuracy with and without the land profile enabled Again the largest gains are seen on the entry level UUT1 so this is the graphic shown below This shows how the error peaks of the azimuth Low Dynamics RMS Errors Profile IMU 2D Pos m Height m TABLE 3 RTK RMS errors for low dynamics 2D Vel m s Up Vel m s Roll deg Parkade Full GNSS Outage 500s RMS Errors Profile IMU 2D Pos m Height m estimates are constrained All the sharp corrections in each plot correspond to the vehicle turning around at the end of each 2 Km line and illustrates how much more powerful a rotation observation can be in azimuth accuracy overall Parking Garage Test This test was carried out at the Calgary International Airport and was selected to show the INS solution degradation during 18 GPS WORLD WWW GPSWORLD COM JUNE 2017 2D Vel m s Pitch deg Yaw deg extended complete GNSS outages The test consisted of an initialization period in open sky conditions to allow the SPAN filter time to properly converge followed by a 500 second period within the parking garage During the interval within the parking garage there were no GNSS measurements available FIGURE 8 provides a trajectory of the test environment The time spent inside the parking structure is evident FIGURE 7 UUT1 attitude error std vs land FIGURE 5 Low dynamics test trajectory FIGURE 6 Low dynamic UUT1 position errors TABLE 4 RTK RMS errors parking garage 500s Up Vel m s Roll deg Pitch deg Yaw deg DEFAULT UUT1 15701 1599 138 011 004 004 035 UUT2 2702 359 029 003 001 001 004 UUT3 218 070 009 001 001 001 008 LAND UUT1 1250 348 030 003 003 005 050 UUT2 819 077 024 002 002 002 018 UUT3 215 089 009 001 001 001 008 DEFAULT UUT1 003 002 001 001 001 001 020 UUT2 002 002 001 001 001 001 007 UUT3 003 002 001 001 001 001 005 LAND UUT1 003 002 001 001 001 001 013 UUT2 002 002 001 001 001 001 007 UUT3 003 002 001 001 001 001 005
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