Hi guys, i hope i landed in the right forum here. I need to work with a DEM in TIN-format with the Spatial Analyst and 3D Analyst extension. Sadly, i can't even get my DEM into ArcMap... So, i will list my problems and hope for some help from such nice people as you certainly are 1) matching coordinate systems of all my data (transforming, projecting) My DEM-data uses GCS_Bessel_1841. Would there be any inaccuracies if i would transform it to DHDN 3-Degree Gauss Zone 3? Or should i rather match all my other data to the DEMs coordinate system? How would i do that? 2) merging layers of raster data of the same format My DEM consists of several different layers lying right next to each other. How can i merge them to one single layer so that i can analyse my whole DEM at once? 3) converting TIN to GRID My DEM comes in TIN-format so that i will have to convert it to GRID to be able to analyse it. Will there be any inaccuracies from converting TIN to GRID? If so, i would have to try to get the DEM in ADF-format... Thank you all so much for your help!