Dem (digital Elevation Model) Production and Accuracy Modeling of Dems from 1:35.000 Scale Aerial Photographs

Aerial photographs and satellite imagery have been evaluated manually by the operators for a long time for the extraction of the contour line and DEM data. Computer technology and digital image processing technologies have been developed and this development provides to perform these extraction processes automatically or semi-automatically. The aim of making the processes automatic is to increase the speed of collecting the data and to reduce the cost. Many researches are made about the production of digital elevation models from different data sources and with different methods. In all of the studies, digital elevation models having different resolutions and different data sources are produced and the accuracies of digital elevation models are investigated. The results of these studies vary according to the source data, resolution, ground control point distribution, production method, topography, and reference data for the accuracy assessment. In this study, digital elevation models are produced by automatic image matching and from contour lines which are compiled from 1:35.000 scale aerial photographs and the accuracies of digital elevation models are assessed. Optimum data collection interval and accuracy of digital elevation models are investigated. Automatic image matching and photogrammetric compilation methods for digital elevation model production are compared. Accuracies are also investigated according to the resolution of digital elevation model and slope of topography. The results showed that the accuracy is correlated highly with digital elevation model resolution and 8 to 16 meters of DEM resolution is appropriate for DEMs produced by automatic image matching from 1:35.000 scale aerial photographs. A higher resolution of DEM does not affect the accuracy of DEM.