Hi, I am new to using ENVI and to remote sensing but I am attempting to mosaic some SRTM data in ENVI. I have downloded 8 DTED files from USGS covering my study area and can read them into ENVI using open extrenal file > digital elevation >DTED the "DTED Input Parameters" box then appears with my files listed, I keep "mosaic files" selected and choose an output filename, a box appears to inform me that "Dimensions of output DEM are computed to be 3601 x 4801 Continue?" I click "Yes" but I'm not sure if that's right? My files are then read in and appear in the "Available Bands" window. However, when I click on "Load Band" nothing appears in the image viewing windows. I then go to the main menu and File > Save File as > Geotiff > select my file, choose and output filename then press OK. I then get the following error message: ENVI Retrieve Data: an error has occurred during processing. Error: "READU: End of file encountered. Unit:101, File:D:\mosaic_all" The result may be invalid. I press OK anyway and a mosaic is made, but I doubt it's right. In addition, I wonder if I should have at some point specified a projection (UTM zone) system to be used? I would greatly appreciate if anyone can advise me on what this error message means and how to avoid it. Cheers, Rachel