topic Re: Flow Accumulation: Gaining Speed in ArcGIS Spatial Analyst Questions https://community.esri.com/t5/arcgis-spatial-analyst-questions/flow-accumulation-gaining-speed/m-p/43250#M547 <HTML><HEAD></HEAD><BODY><BLOCKQUOTE class="jive-quote">Or do the following steps shorten the computation time?<BR />- same cell size<BR />- same projection<BR />- Output float/integer</BLOCKQUOTE><BR /><BR /><SPAN>If the flow direction and weight grid are not in the same coordinate system, and the cell size and snap aren't set to match the flowdirection grid, you are unlikely to get the correct results.</SPAN><BR /><BR /><SPAN>The kind of output will always be float. You may have some performance gain if the weight raster is integer because this could minimize the amount of I/O required to access the values due to the run-length compression used for integer grids.</SPAN><BR /><BR /><SPAN>If both inputs are grids and the output is a grid you probably will see better performance. (Definitely if using 9.x.)</SPAN></BODY></HTML> Tue, 19 Jul 2011 22:25:26 GMT curtvprice 2011-07-19T22:25:26Z Flow Accumulation: Gaining Speed https://community.esri.com/t5/arcgis-spatial-analyst-questions/flow-accumulation-gaining-speed/m-p/43249#M546 <HTML><HEAD></HEAD><BODY><SPAN>Hello,</SPAN><BR /><BR /><SPAN>I need to use the Flow Accumulation tool on a relatively large DEM (30 meter cellsize) with a weight raster (cellsize roughly 900 m), which takes probably some days to finish.</SPAN><BR /><SPAN>Are there any means to speed up the computation proceedure? </SPAN><BR /><SPAN>Or do the following steps shorten the computation time?</SPAN><BR /><SPAN>- same cell size</SPAN><BR /><SPAN>- same projection</SPAN><BR /><SPAN>- Output float/integer</SPAN><BR /><BR /><SPAN>Thanks in advance</SPAN><BR /><BR /><SPAN>-- mrkanister</SPAN></BODY></HTML> Mon, 18 Jul 2011 07:48:56 GMT https://community.esri.com/t5/arcgis-spatial-analyst-questions/flow-accumulation-gaining-speed/m-p/43249#M546 ValentinMüller 2011-07-18T07:48:56Z Re: Flow Accumulation: Gaining Speed https://community.esri.com/t5/arcgis-spatial-analyst-questions/flow-accumulation-gaining-speed/m-p/43250#M547 <HTML><HEAD></HEAD><BODY><BLOCKQUOTE class="jive-quote">Or do the following steps shorten the computation time?<BR />- same cell size<BR />- same projection<BR />- Output float/integer</BLOCKQUOTE><BR /><BR /><SPAN>If the flow direction and weight grid are not in the same coordinate system, and the cell size and snap aren't set to match the flowdirection grid, you are unlikely to get the correct results.</SPAN><BR /><BR /><SPAN>The kind of output will always be float. You may have some performance gain if the weight raster is integer because this could minimize the amount of I/O required to access the values due to the run-length compression used for integer grids.</SPAN><BR /><BR /><SPAN>If both inputs are grids and the output is a grid you probably will see better performance. (Definitely if using 9.x.)</SPAN></BODY></HTML> Tue, 19 Jul 2011 22:25:26 GMT https://community.esri.com/t5/arcgis-spatial-analyst-questions/flow-accumulation-gaining-speed/m-p/43250#M547 curtvprice 2011-07-19T22:25:26Z