topic Re: Raster 'Minus' tool misses cells? in ArcGIS Spatial Analyst Questions

Raster 'Minus' tool misses cells?

ClayLaHatte — Tue, 03 Feb 2015 19:24:34 GMT

Hi,

I am trying to subtract two rasters in Arcmap 10.1 (see attached image); one is an elevation raster (multicolored blue to red), the other contains sparsely spaced individual cells (points raster, smaller dark green and brown cells in the attached image). These sparsely spaced raster cells come from running the 'Point to Raster' tool on a point shapefile.

The 'Minus' tool (as well as subtracting the rasters via Raster Calculator) omits some cells in the solution (there is no resulting cell at the locations of some of the point raster source cells.

The resulting cells after running the 'Minus' tool are in bright green in the attached imaged. Notice there are 5 pont cells, but only 2 of them show a result after the 'Minus' operation.

I have tried making the points raster cell size various sizes, but so far nothing is working correctly.

Any ideas as to why this would happen? A solution?

Re: Raster 'Minus' tool misses cells?

ClayLaHatte — Mon, 09 Feb 2015 16:18:01 GMT

Anyone? Beuller?

Re: Raster 'Minus' tool misses cells?

LisaTurner — Mon, 09 Feb 2015 16:20:53 GMT

Hey Clay,

You might want to move this question into one of the groups so that the right people see it.

Lisa

Re: Raster 'Minus' tool misses cells?

ClayLaHatte — Mon, 09 Feb 2015 16:32:52 GMT

Thanks. I'll try. I can't make sense of this 'forum' layout. Any suggestion on a particular group?

Clay

Re: Raster 'Minus' tool misses cells?

LisaTurner — Mon, 09 Feb 2015 16:36:15 GMT

I would guess this one GIS would be a good place to start and someone in there might be better able to help you.

Re: Raster 'Minus' tool misses cells?

ClayLaHatte — Mon, 09 Feb 2015 16:38:19 GMT

Great. Thanks.

Re: Raster 'Minus' tool misses cells?

XanderBakker — Mon, 09 Feb 2015 16:50:42 GMT

The right place would be Spatial Analyst

Re: Raster 'Minus' tool misses cells?

ClayLaHatte — Mon, 09 Feb 2015 16:54:17 GMT

Thanks.

Re: Raster 'Minus' tool misses cells?

XanderBakker — Mon, 09 Feb 2015 16:55:27 GMT

When you rasterize your point, take a close look at the environments settings. These define how you points will be rasterized. When you are going to combine the points in raster format with another raster, you should consider setting the environment setting to match to the existing raster. See this help topic: ArcGIS Help (10.2, 10.2.1, and 10.2.2)

Extent, Snap Raster and Cell Size should match the extisting raster.

Re: Raster 'Minus' tool misses cells?

ClayLaHatte — Mon, 09 Feb 2015 16:59:45 GMT

So, in essence, it is not possible to subtract rasters with different cell sizes?

Re: Raster 'Minus' tool misses cells?

XanderBakker — Mon, 09 Feb 2015 17:04:17 GMT

It is, but the result might be more difficult to interpret. If you need to use the cell sizes you are using, then there should be a result. In there is not (as in your case) this might be due to the environment setting (extent smaller than the inputs, resulting in a raster containing only part of your data).

You may also want to consider the extract values to points to “join” the values from the other raster to the points and perform the minus in the attribute table of the points

Re: Raster 'Minus' tool misses cells?

ClayLaHatte — Mon, 09 Feb 2015 17:09:38 GMT

Interesting. When I try "Join" on a raster, nothing happens when I select that from the context menu.

I am remaking my rasters to insure they all line up and have the same cell size. That should solve the issue. I hope.

Thanks.

Re: Raster 'Minus' tool misses cells?

XanderBakker — Mon, 09 Feb 2015 17:16:44 GMT

I was refering to this tool: Extract Values to Points (Spatial Analyst)

ArcGIS Help (10.2, 10.2.1, and 10.2.2)

Re: Raster 'Minus' tool misses cells?

ClayLaHatte — Mon, 09 Feb 2015 18:52:50 GMT

Aah. Ok. I'll look into it. Thanks.