Raster and Polygon have different areas after conversion?

Discussion created by aaridd18 on Jul 13, 2012
Latest reply on Jul 16, 2012 by Dan_Patterson
Hi all,

I'm trying to extract crop types from the national-extent Cropland Data Layer (available here: http://nassgeodata.gmu.edu/CropScape/) and convert into polygons for further analysis. The dataset is huge (30m coverage of the entire continental U.S.) and I'm running it on a 64-bit, 4GB machine which generally handles it well. However, on a few of the datasets the conversion is very inconsistent, specifically, the area of the initial raster dataset and final polygon dataset will differ by a LOT--sometimes at least an order of magnitude. It's not consistent either (i.e., converting the same dataset to polygons will get two different answers). I'm using the simple count*pixel size to measure the area of the initial raster, and summary statistics in the attribute table on the Shape_Area field to compare. Is there any known reason the sizes would be so significantly different?