## 4 Validation Results
### DDM Results  
In this section, an analysis of three DDMs is presented. Two DDMs are from WG track 1, and the last is from JER track 1. These DDMs were selected based on their proximity to the in situ sensors and distinct features. The first DDM is sample 70,682 of WG track 1, the third sample from the west. The SP is located at a latitude of \(31.505^{\circ}\) and longitude of \(-110.726^{\circ}\), which is west of the in situ sensors. Figure 10a,b show the normalized CYGNSS DDM and the normalized DDM estimated by the IGOT model, respectively. Furthermore, the elevation map of the area around the SP is shown in Figure 10c. As shown in Figure 10a, this DDM has a strong positive Doppler tail. Despite the complex shape of this DDM, the IGOT model is able to estimate the CYGNSS DDM with good accuracy, which includes generating the DDM horseshoe shape, as illustrated in Figure 10b. However, the intensity of the horseshoe is not captured fully by the model. The IGOT model has the capability of plotting the WAF projection of a specific DDM cell. Two cells within the horseshoe shape are of interest. The first is \((4,2)\), where the reflectivity of this cell is close to the SP reflectivity. The WAF projection of this cell is shown in Figure 10d, which illustrates that the majority of the energy of this cell is from the valleys. The second cell is \((8,-3)\), which was selected due to the relative reflectivity discrepancies between CYGNSS and IGOT. As illustrated in Figure 10e, the majority of the cell energy is from a valley. Figure 8: JER track 1: (**a**) Track elevation map; (**b**) Peak reflectivity. The SoilSCAPE sites are between the orange vertical lines. Figure 9: JER track 2: (**a**) Track elevation map; (**b**) Peak reflectivity. The SoilSCAPE sites are between the orange vertical lines. The second DDM is sample 70,693 of WG track 1, the closest DDM to the Lucky Hills site from the west. This DDM SP is located at 31.724\({}^{\circ}\) latitude and \(-\)110.072\({}^{\circ}\) longitude, with a reported SNR of 5.5 dB. Furthermore, the normalized reflectivities of the CYGNSS DDM and the IGOT model DDM are shown in Figure 11a,b, respectively. Moreover, the elevation map of the area close to the SP location is shown in Figure 11c. This DDM has non-zero cells in the negative delay. In a DDM, no return is expected before the SP. To understand this phenomenon, the WAF projection of cell (\(-\)7, 3) was examined, the cell that has the highest reflectivity in the negative delay part of the DDM. The WAF projection of this cell is presented in Figure 11d. It shows that the cell scattering area is around the CYGNSS reported SP location. On the other hand, the WAF projection of the DDM SP (0, 0) shows that its scattering area is on the west side of the reported SP location, as shown in Figure 11e. This DDM has two strong scattering areas, where the DDM is centered on the strongest. The first scattering area is associated with the reported SP location, which contains the valley, as shown in Figure 11d. The other scattering area is associated with the high elevation area and its slope, as shown in Figure 11e. Figure 10: DDM of sample 70,682 of WG track 1: (**a**) Normalized CYGNSS DDM; (**b**) Normalized IGOT DDM; (**c**) DEM; (**d**) WAF projection of DDM cell (4, 2); (**e**) WAF projection of DDM cell (8, \(-\)3). The third DDM is sample 104,027 of JER track 1. Its SP is located at 32.553\({}^{\circ}\) latitude and \(-106.771^{\circ}\) longitude with an SNR of 8.7 dB. This DDM was selected due to its proximity to the in situ sensors and the SP footprint location. Figure 12d shows the elevation map of the area around the SP. Furthermore, the normalized CYGNSS DDM and IGOT model DDM are presented in Figure 12a,b, respectively. These figures show that the DDM of the IGOT model has a similar shape as the CYGNSS DDM. Furthermore, the WAF projection map of the SP matches the expected shape of a flat region, as shown in Figure 12c. A WAF projection map of a SP of a flat area is expected to have an elliptical shape.