(IDL6.3 - windowsXP) I have a flloat array with dimensions 8100, 6805. Only about 300,000 of those points have values (others are all zero "nodata"). The data set is "georeferenced" (i.e. I know the lower left lat/lon and the # degrees per pixel). I want to be able to do two things: 1) Export this array as an XYZ text file for ONLY the non-zero values. 2) Ideally, I want the text file to have lat/lon, and not column-row (X-Y) locations for each value (Z). In the end, I want to create contours for these data points for eventual import into ArcGIS for further analysis. I know IDL does contouring, but I'm not too familiar with how to use that function. I was planning to have a cooworker use a program he's more familiar with to create the contours, then import them to ArcGIS. What I have so far is something like: pha=fltarr(8100,6805) openr,1,'pdiff1_spf4a_unw_020_geo' readu,1,pha close,1 ;LOWER LEFT lat/long xul=-120.670046296297 yul=36.1200463009315 step=0.000092592593 ;define where pha /= zero nonzero=WHERE(pha ne 0) Thanks for any suggestions! Justin