topic Re: Raster elevation calculation in ArcGIS Spatial Analyst Questions

Raster elevation calculation

PhilippWickey — Sun, 27 May 2018 17:17:20 GMT

Hello,

I have forgotten how to express in the Raster Calculator, that I want elevations " 35m through 100m" from a raster.

Any help is appreciated, also if there is an example reference guide somewhere, please feel free to share.

Thanks

Phil

Re: Raster elevation calculation

DanPatterson_Retired — Sun, 27 May 2018 20:20:26 GMT

("Elev" > 35) and ("Elev" < 100)

or whatever... you grid AND you must reuse the grid's name for both conditions, you can't do "Elev" > 35 and < 100

Re: Raster elevation calculation

PhilippWickey — Sun, 27 May 2018 23:00:29 GMT

Thanks!

Re: Raster elevation calculation

DanPatterson_Retired — Sun, 27 May 2018 23:03:58 GMT

Philipp, no problem... but if it works, mark the question answered so others will know a solution was found

Re: Raster elevation calculation

DanPatterson_Retired — Sun, 27 May 2018 23:24:49 GMT

Almost forgot this related and similar thread

https://community.esri.com/thread/214639-what-is-the-proper-syntax-for-pulling-elev-ranges-in-raster-calculator

Re: Raster elevation calculation

PhilippWickey — Mon, 28 May 2018 05:31:03 GMT

I wish I could say it worked, but it did not. I tried a few other options like using "&" etc., but did not find a combination that worked. I also tried the instructions in the link you provided. Thanks again. (p.s. the other two rasters are just simple queries made from "bells" < 3000 and "bells" > 3500. "bells" is a DEM just to clarify.

Re: Raster elevation calculation

DanPatterson_Retired — Mon, 28 May 2018 05:59:36 GMT

Did you 'type' the expression? Always select the grid from the list of layers and variables, then select the operands and numbers like on a calculator. In that way, the expression will be correct.

Try

Con((bells >= 3150) & ( bells < 3400), 1, 0)

no typing... except for the grid name... and try a *.tif in a folder rather than a geodatabase (ie c:\GISwork\...\rast6.tif

Re: Raster elevation calculation

PhilippWickey — Mon, 28 May 2018 06:04:43 GMT

I did not type the expression (except for the word "and" and the commas)

Re: Raster elevation calculation

PhilippWickey — Mon, 28 May 2018 06:11:09 GMT

That worked! The formula looks like the following:

Con(("bells" >= 3150) & ( "bells" < 3400), 1, 0)

Very happy, thanks!

Re: Raster elevation calculation

PhilippWickey — Mon, 28 May 2018 06:16:15 GMT

I have not attempted this yet, but I will now need to multiply this .tif with a slope, aspect and one other raster. Do you foresee any problem multiplying a raster and a .tif? Thanks again!

Re: Raster elevation calculation

DanPatterson_Retired — Mon, 28 May 2018 06:57:38 GMT

A *.tif is just a form of raster.

What you have to worry about is making sure that the extent, cell size and snap raster are set BEFORE you begin any raster work.

This is done in the Environments tab of any tool in the spatial analyst tools.

It is easy to get results.... it takes work to get proper results

Re: Raster elevation calculation

PhilippWickey — Mon, 28 May 2018 17:05:41 GMT

Got it,

One thing, I do not remember having to save a file in a different folder or as a .tif file.

I am curious if this situation is just an unusual quirk or something else.

Thanks again, and best!

Re: Raster elevation calculation

DanPatterson_Retired — Mon, 28 May 2018 17:40:02 GMT

I know tiffs work... sometimes there are squeaky things with rasters in a file geodatabase... and you can always copy to the gdb if you really must... but I organize everything in one project folder... so it is a quick zip and ship to archive if need be

Besides tiff's can be used in other applications whereas rasters in a gdb are not

Re: Raster elevation calculation

PhilippWickey — Mon, 28 May 2018 17:54:57 GMT

Those are some good things to consider and I had not thought of.

BUT, it also leads to a couple more questions for me (slightly different tangent here);

1) .tif vs .tiff, is there going to be a difference (for calculations) in which format I save it? (I suspect no is the answer since they are essentially the same thing, I just am not certain Arc reads them the same)

2) I have wondered about the benefit of a gdb. Am I OK/safe with saving rasters etc to a folder vs a gdb? I often do, and it does not seem to present an issue.

Also, thanks for being really helpful!