GPS World, June 2017

TABLE 1 Summary of coordinate differences between the IMU slow walking positioning results and the rectified raster image results For comparison of the IMU results in an outdoor environment a professional drone was used see FIGURE 3 to take a vertical image of the test area see FIGURE 4 Precise raster rectification of the image was carried out using Softlines C GEO v 8 geodetic software This operation is usually done by loading a raster image file and entering a minimum of two control points for a Helmert transformation or a minimum of three control points for an affine transformation on the raster image for which object space coordinates are known These points are entered into a table After specifying a point number appropriate coordinates are fetched from the working set Next the points in the raster image corresponding to the entered control points are indicated with a mouse For our test we measured four ground points using a GNSS receiver marked in black in Figure 4 to be easily recognized on the raster image when zoomed in A pre existing base station on the roof was also used To compute precise static GPS GLONASS BeiDou positions of the four ground points we used post processing software During the GNSS measurements 16 satellites were visible After post processing of the GNSS data the estimated horizontal standard deviation for all points did not exceed 001 meters The results were transformed to the UTM zone 50 grid system For raster rectification we used the four measured terrain points as control points After the Helmert transformation process the final coordinate fitting error was close to 002 meters For comparing the results of the three different walkingspeed experiments IMU stepping points floor lamps were chosen as predetermined route points with known UTM coordinates which were obtained after raster image rectification in the geodetic software marked in red in Figure 4 After synchronization of the IMU with ZUPT and ZARU and precise image rectification positions were determined and are plotted in Figure 4 The trajectory reference distance was 151 meters PDR positioning results of the slow walking test with ZARU and ZUPT corrections were compared to the rectified raster image coordinates The coordinate differences are presented in FIGURE 5 and TABLE 1 The last two parts of the experiment were carried out to test normal and fast walking speeds The comparisons of the IMU positioning results to the true positions extracted from the calibrated raster image are presented in FIGURES 6 and 7 and TABLES 2 and 3 From the presented results we can observe that the processed data of the 100 Hz IMU device provides a decimeter level of accuracy for all cases The best results were achieved with a normal walking speed where the positioning error did not exceed 016 meters standard deviation It appears that the sampling rate of 100 Hz makes the system more responsive to the authenticity of the gait However we iSXBlue II GNSS Maximize your field data t info@ sxbluegps com 1 800 463 4363 Compatible with Collector for ArcGIS Oil Gas Forestry Electric Distribution Water Resources Environment Telecommunications GPS GLONASS BeiDou SBAS Bluetooth The most reliable Real time sub meter GNSS receiver 62 GPS WORLD WWW GPSWORLD COM JUNE 2017 TABLE 2 Summary of coordinate differences between the IMU normal walking positioning results and the rectified raster image results TABLE 3 Summary of coordinate differences between the IMU fast walking positioning results and the rectified raster image results Delta x meters Delta y meters Minimum 018 004 Maximum 044 094 Standard deviation 016 032 Delta x meters Delta y meters Minimum 016 027 Maximum 018 025 Standard deviation 009 016 Delta x meters Delta y meters Minimum 021 011 Maximum 022 055 Standard deviation 014 020