[UW-GIS-L] Raster calculator question

[Stefan E. Coe]

You can use the following syntax to turn your no data values to zero while mainting your non no-data values. Before doing this, make sure to set the extent of you analysis to the larger raster (if one has a larger spatial extent than the other) to ensure that any gaps in extent are treated as zero and not nodata in subsequent analysis.

con(isnull([grid1] == 1), 0, grid1)




Stefan Coe
GIS/Remote Sensing Analyst
Urban Ecology Research Lab
University of Washington
206-616-9379

On Wed, 30 Aug 2006, Sara Dubowsky wrote:

> Hi.
>
> We have two raster layers that we are trying to sum together to make one 
> cumulative layer.  The problem is that one of those layers has more data than 
> the other.  Is there some way to tell GIS to assign zero to a missing value 
> when it takes the sum?  Alternatively, is there a way to make some type of if 
> statement that says:
>
> if layer1 = . then output = layer2
> else output = layer1 + layer2?
>
> We tried to make some type of logical statement but it did not seem to take 
> such programming. We apologize if this is an easy issue, we're still a bit new 
> to GIS.
> Thanks!!
> sara
>
>
> -- 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Sara Dubowsky
> Research Fellow
> Department of Environmental and Occupational Health Sciences
> University of Washington
> 4225 Roosevelt Way, Suite 302
> Seattle, WA 98105
> phone: 206-221-5932
> fax: 206-685-3872
>
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