Using a sub-pixel/pixel spatial attraction model for landform classification

The most important subject in quantitative geomorphology is increasing of spatial resolution to increase the information in the digital elevation model (DEM). Different models have been used to improve the spatial resolution. Among the different models, sub-pixel/pixel spatial attraction model as the newest model is very high accuracy. In the study area was used the sub-pixel/pixel spatial attraction model for the first time to improve the spatial resolution DEM in the southern city of Darab (Qalatuyeh). The sub-pixel attraction models convert the pixel towards sub-pixels based on the fraction values in neighboring pixels that can be attracted only by central pixel. Based on this approach only a maximum of eight neighboring pixels can be selected for the attraction. In the model other pixels are supposed to be far from the central pixel to have any attraction. In this study by using sub-pixel attraction model the spatial resolution of digital elevation models (DEM) was increased. The design of the algorithm is accomplished by using digital elevation model (DEM) with spatial resolution of 30 m (Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)) and 90 m (Shuttle Radar Topography Mission (SRTM)) in the north of Darab, Fars province, Iran. In attraction model scale factors of (2,3,4) with two neighboring methods of touching and quadrant are applied to DEMs using Matlab. As the result, it showed that the  spatial attraction model with scale factor of (S=3) gives better results compared to scale factors that are greater than 2 and also touching neighborhood method proved to be more accurate then quadrant (RMSE=8.07). In fact, subtracting each pixel to more than two sub-pixels caused to decrease the accuracy of resulted DEM which makes to increase the value of root-mean-square error (RMSE) and showed that attraction models could not be used for S which is greater than 2. So according the results is suggested that used the model for increasing spatial resolution of DEM in the studies catchment. In order to preparing the geomorphology map using topographic position index (TPI) used DEM with scale factor of (S=3) and touching neighboring as input data (the new DEM with high spatial resolution) in the GIS software. Also the results show that areas of mountain tops, high ridges, local ridges/hills in valleys, upper slopes, mesas, open slopes, plains small, u-shaped valleys was more than DEM 90 in sub-pixel model. While the area of midslope ridges, small hills in plains,, upland drainages, headwaters, midslope drainages, shallow valleys, canyons, deeply incised streams lower than DEM 90 in sub-pixel model.  The results of landform classes were extracted by using TPI with the new DEM and the extracting of attraction model showed that landforms have more details and are separable than the landform map preparing with DEM 90m.