Digital terrain model: Elevation extraction and accuracy assessment

This paper discusses different techniques (analytical, manual, and automatic digital) of extracting digital terrain models (DTMs) and their error evaluation. DTMs are mainly used for orthorectification of images, topographic mapping, and engineering design and modeling. Prior to using DTMs for various applications, it is prudent to analyze errors of the extracted DTMs to ensure that they meet the required accuracy standards. DTM data, for about 500 points for a 20 x 50 m grid, were collected using different modes (static, fast static, stop-and-go kinematic) of global positioning system (GPS) surveys on a study area of approximately 0.7 km x 1.0 km in Lavonia, Georgia. Two stereo models at a scale of 1:3,000 have been used to capture DTM and planimetric data on the same study area using three different digital and one analytical photogrammetric systems. These data are compared and analyzed for their compliances with required accuracy standards for orthorectification as well as engineering/topographic mapping. Comparison of analytical and digital photogrammetric systems is made to evaluate accuracy of different systems. Also, a comparison of analytical versus automatic DTM collection was made in four pilot areas using different grid sizes for automatic DTM collection.