Spatial Analyst -- Viewshed Problems

Discussion created by chuckbr24 on Jul 13, 2010
Hello, this is my first post on these forums (they have been very, very helpful so far).

Posted this on the Geoprocessing forum as well.

I need to get viewsheds for multiple tower locations in an area, so that our Field Wireless team can decide where is the best place to put a tower in order to get the best coverage.

We would like to automate this process, so the Field Wireless guys can run this on their own (without being GIS savvy) and so a GIS Support member doesn't have to stop his/her work to create one of these for the FW people (very time consuming, labor intensive, etc.)

1. So I am in the process of building a Viewshed model/script that will take an input .csv file from the user (with a list of tower names, latitude, longitude, OFFSETA (tower height), OFFSETB (receiver height), RADIUS1 (minimum radius), RADIUS2 (maximum radius)).

2. Then it will turn that .csv into a shapefile containing all the locations.

3. Then it will break apart that shapefile into a seperate .shp for each location. (I used Dan Patterson's shapefile break Python code for this) THANKS!

4. Then loop through each new .shp and run viewshed analysis on it. Then to account for trees I MINUS the areas with tree cover from the viewshed output to get the final result. (I repeat this process for all locations inputed)

This model works fine, but I am now getting odd results when running Viewshed Analysis through the model or through the tool in ArcMap.

I get an expected result when using my original .shp files from a few weeks ago.

When using the .shp that I create in the model though, I get for some locations a result that is way off. For some locations it is much better, but still is not the exact same as when using the old shapefiles.

I am baffled by this because when examining the attribute tables of both, they are identical.
Does anyone think that they can help me?? I am really struggling with what the problem could be.

Sorry about being so lengthy, but if anyone has any ideas about the problem I would really appreciate some help. (I am working in 9.3 by the way)