Accuracy of difference associated with grid digital elevation model

Difference is the key method for deriving topographic parameters from grid digital elevation model (DEM). Its accuracy is the vital factor affecting the accuracy of topographic parameters. The research validated that the accuracy of difference is associated with topographic surface complexity, difference algorithm, DEM data accuracy and DEM data property including grid orientation, grid size, grid origin and data precision. The high accuracy results of difference could not derived from small grid size DEM if there are DEM data errors. There is one and only suitability DEM grid size which the difference calculation has the least RMSE (root mean square error). The research further perfects the theory and method of accuracy analysis in digital terrain analysis.