The Study And Application Of DEM Error Model Based On The Reconstructed Contours

Digital Elevation Model (DEM) is a kind of discrete digital expression to the terrain relief of the earth surface. As the important spatial information in geographical database, DEM plays a more and more important role. The quality of DEM will directly influence the accuracy of the analysis and the reliability of the applications in the geography information system. Therefore, the accuracy of DEM becomes one of the DEM research focuses, and it's very important in theoretics and applications.In this paper, based on the contours, the accuracy of DEM is analysed and evaluated by the reconstructed contours. The main contents and innovations are as follows:1. For the DEM based on Grid and TIN models, some methods are developed to optimize the reconstructed contours and reflect the varieties of the surface of DEM.2. Based on the algorithm of interpolating contours, some methods are designed and realized to restore the fractured contours automatically and transform the contours from metric ones to English ones. The experiments indicate that the restored and transformed contours can express the terrain perfectly.3. By the analysis to the DEM error model based on the reconstructed contours, one new index—the maximal excursion error of the reconstructed contours—is proposed, and then the DEM error model becomes perfected. Where some methods are also brought forward:1) The grid-fractionizing method is developed to exactly reconstruct the contours on the surface of Grid-DEM;2) The similitude measurement of contours is proposed to effectively confirm the relation of reconstructed contours and original ones;3) An algorithm to get the error of the unclosed reconstructed contours is put forward, which can close the non-closed contours by the borderline.At the same time, by the actual terrain data, the developed DEM error model is confirmed effective, and the model is compared with the Root Mean Square Error model.4. Based on the reconstructed contours, the accuracy of multi-resolution DEM is studed. According to the results of the accuracy evaluation of multi-resolution DEM, the error formulae of different relief are obtained.