GIS5935: DEM Accuracy

The purpose of this lab was to determine the accuracy of a Digital Elevation Model. In order to do this, first, "true" test points had to be acquired. For this project, this consisted of field data collected using high-accuracy survey methods. The test points were essentially combined with the DEM using the Extract Values to Points tool in ArcGIS. Then, the elevation of the DEM at each point was compared to the true elevation. Using an Excel spreadsheet, the DEM's elevation was subtracted from the field data to find the difference, and this was used to find statistics for the Room Mean Square Error, the 95th percentile, and the 68th percentile. The results can be observed and compared to each Land Cover classification to find trends and consistencies within each type and help to determine any bias. Below are the results for this particular analysis:

Land Cover:                         A                             B                             C

Sample Size:                       48                           55                           45          

Accuracy 68^th:                    0.001                     0.023                     0.049                               

Accuracy 95^th:                    0.027                     0.194                     0.233

RMSE:                                   0.105                     0.181                     0.246    

                                              

Land Cover:                        D                             E                              Combined

Sample Size:                       98                           41                           287

Accuracy 68^th:                    0.051                     0.035                     0.029

Accuracy 95^th:                    0.214                     0.147                     0.185

RMSE:                                   0.394                     0.199                     0.276