Hi Andrzej, there is no predefined size for HGT's. I use 1201-HGT's mixed with 3601'HGT's. It should not to be a problem to use any other size. The only restriction is: height==widht. The memory consumption is a problem. A HGT with 1201x1201 need in memory 1201*1201*4 Byte = 5,5 MB (.NET use for short also 4 byte). 200 HGT's need 1,1 GB. Hard to estimate is the size for DEM-Data. The prog is compiled as "any cpu" and "prefer 32-bit". If "prefer 32-bit" not set, run the prog in 64-bit-win as 64-bit-prog and can use more memory. But it runs slower. If you self compiled the prog, unset the option and try to use a xml-file BuildDEMFile.exe.config like this: <?xml version="1.0" encoding="utf-8" ?> <configuration> <runtime> <gcAllowVeryLargeObjects enabled="true" /> </runtime> </configuration> But you are allright, downsizesing the HGT's "on the fly" should not to be a problem. Let me a little bit think about that. Frank --- Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. https://www.avast.com/antivirus