how to extract perimeter cells from raster

Discussion created by cathyrl on Feb 28, 2012
Latest reply on Mar 27, 2012 by cathyrl
Hi all,

I've got a raster dataset from which I need to extract all the cells representing the perimeter (the raster is of runoff, and I need all coastal runoff).  I was thinking that I could query cells that neighbor a null value (non-land is null value), but I don't know how to craft such a query, or if there's a tool already in place to do this.  Any other ideas of how to select perimeter cells?