2008 Volume 21 Issue 2 Pages 114-125
The soil microtopography has a great impact on soil-water interactions during rainfall. The objectives of this study were to develop methods to rectify the digital elevation model (DEM) generated by the automated digital photogrammetry system and to apply these methods in monitoring the changes in soil microtopography during rainfall. Two rectification methods were used in order to detect and eliminate the DEM errors. The first method was the reference surface method (RSM), which was developed as a part of this study to detect the DEM errors prior to interpolation. The second was the parametric statistical method (PSM), which was used to detect and rectify the DEM errors after interpolation. The DEMs accuracy was assessed using the difference between the measured and photogrammetrically estimated checkpoints coordinate and elevation (x, y and z, respectively) values. The root mean square error (RMSE) in x-direction, y-direction and z-direction of the checkpoints were 2.08, 2.59 and 1.96 mm, respectively. The changes on the soil surface were assessed using three roughness indices. The soil surface random roughness (RR), the limited elevation difference (LD) and the limited slope (LS) indices decreased with the time. The automated digital photogrammetric system with the rectification methods accurately generated three dimensional (3D) visions of the soil microtopography during rainfall. It gives a new insight for monitoring the changes of soil microtopography and the effects on soil-water interaction processes.
