topic Re: Mask from polygon feature class in Science Questions https://community.esri.com/t5/science-questions/mask-from-polygon-feature-class/m-p/871330#M120 <HTML><HEAD></HEAD><BODY><P>in the environments.&nbsp; You can set the mask to anything you want depending on the function to obliterate what is underneath.&nbsp; So functions might prefer nodata cells since they might not perform calculations in areas of nodata.&nbsp; Others can be used in an operation involving a product since 0 times something gives 0 (unless of course you already have 0 in the data set.&nbsp; So specify what you want depending on what you want to keep and what you are doing</P></BODY></HTML> Tue, 12 Dec 2017 16:34:29 GMT DanPatterson_Retired 2017-12-12T16:34:29Z Mask from polygon feature class https://community.esri.com/t5/science-questions/mask-from-polygon-feature-class/m-p/871329#M119 <HTML><HEAD></HEAD><BODY><P>Hi everyone,</P><P>I am new to ArcGIS and I need to perform a spectral index on&nbsp;dataset of Landsat images. This index performs better when done in a mask.&nbsp;The shapefile I want to use&nbsp;as a mask is a binary raster polygon,&nbsp;(0 and 1)&nbsp;where I want&nbsp;to perform the index on the polygons with the "1" value. Is that mask simply specified in the environments prior to execute the index, or is more complicated?</P><P></P><P>thanks!</P></BODY></HTML> Tue, 12 Dec 2017 16:17:48 GMT https://community.esri.com/t5/science-questions/mask-from-polygon-feature-class/m-p/871329#M119 HugoCrites 2017-12-12T16:17:48Z Re: Mask from polygon feature class https://community.esri.com/t5/science-questions/mask-from-polygon-feature-class/m-p/871330#M120 <HTML><HEAD></HEAD><BODY><P>in the environments.&nbsp; You can set the mask to anything you want depending on the function to obliterate what is underneath.&nbsp; So functions might prefer nodata cells since they might not perform calculations in areas of nodata.&nbsp; Others can be used in an operation involving a product since 0 times something gives 0 (unless of course you already have 0 in the data set.&nbsp; So specify what you want depending on what you want to keep and what you are doing</P></BODY></HTML> Tue, 12 Dec 2017 16:34:29 GMT https://community.esri.com/t5/science-questions/mask-from-polygon-feature-class/m-p/871330#M120 DanPatterson_Retired 2017-12-12T16:34:29Z