Converting ascii data to contour using spatial analyst

Question

Hi,

I'm trying to convert ascii data to a contour shape file, so it can be used in CAD.

I've manage to do this using the contour function in Spatial Analyst. However, the resulting file if enormous, around 2GB. This is from an ascii file that was around 120MB. I would be very grateful if someone could tell me how to convert it without resulting in a such a large shape file - something that was around the same size as the ascii would be more manageable. I'm confused as to why the resulting shape file is so large, so any explanations of that would be equally appreciated!

Many thanks,

Nick

DanPatterson_Retired · Accepted Answer

You didn't specify the range of values in the ascii (min, max) nor the contour interval you chose...both of these will have a big influence on the number of contours.  Also, did you just convert the ascii to a raster, then do the contouring or was there an interpolation involved inbetween.