topic Re: Missing output from 'Visibility' Tool in ArcGIS Spatial Analyst Questions

Missing output from 'Visibility' Tool

DuncanRager — Mon, 21 Jul 2014 19:07:58 GMT

I am running ArcMap 10.2 and have been trying to complete a fairly large viewshed analysis and have chosen to use the visibility tool in order to be able to produce an optional above-ground-level (AGL) layer which will be the focus of further analysis.

The visibility is from a layer consisting of 2 points and the raster is a DSM. I have run several repetitions of this tool (both 3D Analyst & Spatial Analyst) and every time the process completes successfully producing a viable viewshed, but there is never any AGL to be found. There are no errors accompanying the completion of the tool either.

Why would this be? How do I get the tool to produce an AGL? I have tried using only one viewer point as opposed to two without any difference in the outcome.

Thanks,

Colin

Re: Missing output from 'Visibility' Tool

DanPatterson_Retired — Mon, 21 Jul 2014 19:34:03 GMT

What is the height of your observer points? ArcGIS Help (10.2, 10.2.1, and 10.2.2)‌

Re: Missing output from 'Visibility' Tool

DuncanRager — Mon, 21 Jul 2014 20:00:16 GMT

Point one has a 146 z-value and point two has a 121 z-value, both are in feet, and have a 6 foot observer offset.

As a side note, I've run this process successfully before with different data, using the same parameters. Would the use of two viewer points possibly be an issue?

Thanks,

Colin

Re: Missing output from 'Visibility' Tool

DanPatterson_Retired — Mon, 21 Jul 2014 20:09:09 GMT

According to the first line of the help thread I forwarded...

"A viewshed identifies the cells in an input raster that can be seen from one or more observation locations."

it shouldn't. Are your field names correctly named in the source file?

Re: Missing output from 'Visibility' Tool

IanMurray — Mon, 21 Jul 2014 20:15:08 GMT

Multiple viewpoints shouldn't matter, and your testing on a single viewpoint had the same issue, so that shouldn't be a problem. Even if all the points on your raster were visible, it should still make the AGL raster, they would all have 0 values though. Is the raster being created on the hard drive and just not adding to the display?

Re: Missing output from 'Visibility' Tool

DuncanRager — Mon, 21 Jul 2014 20:21:50 GMT

@Dan: We have read the help file and still cannot solve our issue. Which field name are you referring to?

@Ian: No the raster is not being created in the hard drive.

Thanks for the help.

Re: Missing output from 'Visibility' Tool

DanPatterson_Retired — Mon, 21 Jul 2014 20:32:00 GMT

My usage of this tool is to specifically add appropriate fields to the observer points containing the required information...You can glean what is needed from the inputs to the tool and by the code sample towards the end...several of the inputs are fields...

Re: Missing output from 'Visibility' Tool

IanMurray — Mon, 21 Jul 2014 20:34:46 GMT

According to the tool help, they can be fields or numerical values, so it is completely acceptable to just put in an offset of 6.

"It can be a field in the input observer features dataset or a numerical value. By default, a numerical field OFFSETB is used if it exists in the input observer features attribute table. You may overwrite it by specifying another numerical field or constant"

What format are you putting the AGL in? Maybe try changing the file format for the output(I'm grasping at straws here).

Re: Missing output from 'Visibility' Tool

DanPatterson_Retired — Mon, 21 Jul 2014 20:38:43 GMT

grasping too...if it is a esri grid output, does the path and grid name conform to convention? (ie no spaces < 13 characters in name length, path contains a space etc etc)

Re: Missing output from 'Visibility' Tool

DuncanRager — Tue, 22 Jul 2014 14:31:59 GMT

Hey guys,

We were using a tif extension, and have taken your suggestion to use some other extensions and file names, but to no avail. We'll keep trying things and let you know.

Thanks again,

Colin