topic Re: Calculating Topographic Exposure with Raster Calculator in Data Management Questions https://community.esri.com/t5/data-management-questions/calculating-topographic-exposure-with-raster/m-p/160654#M8967 <HTML><HEAD></HEAD><BODY><SPAN>The reason why your equation is failing is that you are using the syntax that grass uses.</SPAN><BR /><BR /><SPAN>dem[4,0] means nothing in ArcMap and is an invalid syntax.</SPAN><BR /><BR /><SPAN>Reading the web page you linked to it seems that this syntax is all to do with calculating some off-set.</SPAN><BR /><BR /><SPAN>I'm not sure if this is a red herring as my raster processing skills is not as good as my vector skills but I know you can shift a grid using the Shift tool. Or maybe someone can suggest some whizzy way of using focal stats?</SPAN><BR /><BR /><SPAN>Duncan</SPAN></BODY></HTML> Fri, 14 Mar 2014 13:38:59 GMT DuncanHornby 2014-03-14T13:38:59Z Calculating Topographic Exposure with Raster Calculator https://community.esri.com/t5/data-management-questions/calculating-topographic-exposure-with-raster/m-p/160653#M8966 <HTML><HEAD></HEAD><BODY><SPAN>I need you help trying to calculate </SPAN><STRONG>Topographic Exposure</STRONG><SPAN> (TOPEX) on a DEM in ArcGIS.&nbsp; I am trying to figure out </SPAN><STRONG>wind exposure</STRONG><SPAN> on a DEM with 25m cells.</SPAN><BR /><SPAN>There is a great blog post where someone explains how to do it but he uses GRASS. </SPAN><A href="http://jamiepopkin.blogspot.ca/2011/01/calculating-togographic-exposure-with.html">http://jamiepopkin.blogspot.ca/2011/01/calculating-togographic-exposure-with.html</A><SPAN>I thought I would be able to put the same equation into ArcGIS Raster Calculator but it says the equation is invalid. I've tried playing with it as much as I can but I can't seem to make it work. </SPAN><BR /><BR /><SPAN>His first equation is:&nbsp;&nbsp;&nbsp; r.mapcalc incl4north = "atan(((dem - dem[4,0])) / ((25 * 4)))"</SPAN><BR /><SPAN>And then he goes on to string a bunch of them together </SPAN><BR /><SPAN>[ATTACH=CONFIG]32197[/ATTACH]</SPAN><BR /><SPAN>Does anyone know how the equation should appear in Raster Calculator in either ArcGIS or QGIS?</SPAN><BR /><SPAN>I am super grateful for any assistant that anyone could provide</SPAN></BODY></HTML> Fri, 14 Mar 2014 13:13:51 GMT https://community.esri.com/t5/data-management-questions/calculating-topographic-exposure-with-raster/m-p/160653#M8966 MaryLynn_Tobiasz 2014-03-14T13:13:51Z Re: Calculating Topographic Exposure with Raster Calculator https://community.esri.com/t5/data-management-questions/calculating-topographic-exposure-with-raster/m-p/160654#M8967 <HTML><HEAD></HEAD><BODY><SPAN>The reason why your equation is failing is that you are using the syntax that grass uses.</SPAN><BR /><BR /><SPAN>dem[4,0] means nothing in ArcMap and is an invalid syntax.</SPAN><BR /><BR /><SPAN>Reading the web page you linked to it seems that this syntax is all to do with calculating some off-set.</SPAN><BR /><BR /><SPAN>I'm not sure if this is a red herring as my raster processing skills is not as good as my vector skills but I know you can shift a grid using the Shift tool. Or maybe someone can suggest some whizzy way of using focal stats?</SPAN><BR /><BR /><SPAN>Duncan</SPAN></BODY></HTML> Fri, 14 Mar 2014 13:38:59 GMT https://community.esri.com/t5/data-management-questions/calculating-topographic-exposure-with-raster/m-p/160654#M8967 DuncanHornby 2014-03-14T13:38:59Z