I am guessing you are referring to SRTM3, not STRM3, no? IDL certainly has the tools to parse such files, but, to parse them, the IDL programmer has to have the details on how those files are formatted. The IDL programmers at ENVI know. the ENVI interface has a built-in reader for SRTM3 data (File -> Open External File -> Digital Elevation -> SRTM DEM). So, if you have access to ITT VIS's ENVI product, that would be the way to go. If you know that your SRTM3 files are pure binary data, and you know how those binary values are laid out (what datatype, how many rows by how many columns of data), then IDL could extract the data in just a few lines of code using routines like READ_BINARY (coupled probably with BINARY_TEMPLATE) or READU. Check out IDL's Online Help 'Contents tab page -> User's Guides -> Getting Started with IDL -> Reading and Writing Data -> Reading and Writing Binary Data'. James Jones