I have about 150-160 DEM images I want to combine into 1 new raster. I keep getting Error 999999, I have 32 bit float selected. I am using Arc Pro 2.8.1. I don't even know if this is enough information to help.
Are they all 32 bit floats?
try 2 ... do you get the same error? Add some more. You may be running out of memory
maybe try this instead ... Mosaic datasets—ArcGIS Pro | Documentation
