topic Extract by mask OUTSIDE in ArcGIS Spatial Analyst Questions

Extract by mask OUTSIDE

EleanorFerguson — Wed, 14 Mar 2012 16:31:47 GMT

Is there a way to get Extract by Mask to extract the area OUTSIDE?
I want to use Extract by Polygon with extraction area = OUTSIDE, but my polygon is in a feature class (too many vertices to input manually) so I have to use Extract by Mask. Is there a way to quickly import the XY coordinates from the feature class, rather than 1 by 1?
Or can someone suggest another way to remove the area inside the polygon from my DEM?
Thanks!

Re: Extract by mask OUTSIDE

TarunJaiswal — Wed, 14 Mar 2012 17:31:26 GMT

Greeting!

If you have access to ArcGIS 10. You can use the Mask button on the Image Analysis window to get your desired output.

The masked output is added as a temporary raster layer to the table of contents. Next, please export the temporary raster (right click > Data > Export Data).

Hope this helps.

Tarun

Re: Extract by mask OUTSIDE

GayathriAlallasundaram — Wed, 14 Mar 2012 17:34:57 GMT

Hi,

You could use the mask tool from the Image Analysis Window under the Processing tab.
The output is added to ArcMap table of contents, and this output is a temporary one, you will have to right click on the output and choose Data > Export Data to make it permanent. Please see this video for reference.http://screencast.com/t/xTSlWveYqd4

-Gayu

Re: Extract by mask OUTSIDE

curtvprice — Thu, 15 Mar 2012 03:44:49 GMT

Is there a way to get Extract by Mask to extract the area OUTSIDE?
I want to use Extract by Polygon with extraction area = OUTSIDE, but my polygon is in a feature class (too many vertices to input manually) so I have to use Extract by Mask. Is there a way to quickly import the XY coordinates from the feature class, rather than 1 by 1?
Or can someone suggest another way to remove the area inside the polygon from my DEM?
Thanks!

Creating a raster mask may be what you want to do. I think this approach may be more likely to give you a good "snap" (cell alignment) than the image toolbar approach.

Set the extent, snap, cellsize environment to your DEM raster

Convert your polygon to a raster, "pgrid". This gives you NoData for areas you want and a value inside the area you want to remove. It's a good idea to stop at this point and make sure you have what you want (or I should say, the opposite -- the NoData areas in this grid are those you will keep).

Use the Reclassify tool (or in 9.3, Reclassify in the SA toolbar) to convert the NoData to a 1 and your data cells to NoData.

Use this as your mask for Extract By Mask.

Another approach is to do steps 3 and 4 using Map Algebra instead:

Con(IsNull("pgrid"),"demgrid")