# Improved 2D Ground Target Tracking in GPS-Based Passive Radar Scenarios
## 6 Results with Real Data
### Results  
In this subsection, some results of ground target detection with the PR using GPS satellites as IoO are presented to demonstrate the actual system performance in the radar scenario. The first result to be described correspond to the detection of a cooperative target in the radar scenario. Figure 10(a) plots the RDM for the first single element of the surveillance array at CPI = 9. At this instant, the target echo was at 24 m bistatic range and the Doppler  
Figure 10: Trials radar scenario: (**a**) top view with PR location, satellite direction (PRN32), area of interest (green area), cooperative target trajectory from GPS data (purple line), buildings and sport facilities details are shown in pictures with their associated area; (**b**) ground view of the AoI, cooperative vehicle and PR receiver deployment. shift was \(-60\) Hz, with a CAF level of 118 dB. The target echo shows a range extension with a starting point outside the CAF range limits and an end point at approximately 100 m. This echo extension is explained by the difference between the GPS signal bandwidth (2 MHz) and sampling frequency (25 MHz), and the size of the range bins (12 m). Figure 11b shows the RDM when the first step spatial filtering is applied, for the beam in which the higher target return is obtained (beam pointing to 12.5\({}^{\circ}\), because the target was expected at 10\({}^{\circ}\)). The target's echo level increases by approximately 6.5 dB, up to 125.64 dB. To obtain a more accurate estimation of the target range, the ambiguity function was approximated to a parabola, using 5 level points of the RDM around the echo's maximum. The range at which the maximum of the interpolating function is obtained, is the estimated target location, equal to 18.48 m for this time instant, whereas the target's range obtained from its GPS data was 20.60 m.  
Figure 12 plots the complete detection results, in both the measurement and the tracking space, with one cooperative target, and two non-cooperative targets in the AoI (the results corresponding to the cooperative target are highlighted in green colour). Because the selected road of interest belongs to the university campus and its traffic density is low, only 2 non-cooperative targets performed movements during the acquisition time. The results of detection and tracking of the non-cooperative targets are depicted in Figure 12 with blue and red colours. The PR configuration allows detection of all targets up to a maximum bi-static distance of 118 m (Figure 12a). However, the presence of the non-cooperative targets only in the last part of the acquisition slightly reduces the number of detection points. The cooperative target was detected at 24 CPIs at the beginning of the acquisition, while the non-cooperative targets were detected at 11 and 19 CPIs, and were no longer detected at the end of the acquisition. Figure 12b shows the targets' location estimation on the local Cartesian space centred in the PR receiver and with the North direction following the Y-axis. As it was expected from targets' detections in the RDMs, the cooperative target reaches the higher detection distances from PR location (98 m) due to its movement was performed during the beginning of the acquisition and overpassed the detection coverage. The detection range for non-cooperative targets remains lower (68 m and 55 m) due to their movements along the AoI were carried out at the end of the measurement, and could not overpass the detection coverage before the end of the acquisition. Figure 11: Real radar data results: first stage spatial filtering. (**a**) RDM from single array element. (**b**) RDM after beamforming (12.5\({}^{\circ}\) beam). The targets' location estimations in the local Cartesian spaces were transformed to the geodetic coordinates for easy integration into the Google Earth application. Figure 12(a) depicted the Google Earth view of the localization results obtained for the cooperative target in comparison with the target's trajectory from GPS data in the radar scenario.