Create a Model that will iterate viewsheds of several sites. When doing this lab under ArcGIS v10, we can run the sites as a single shapefile. When doing this under v9.3 it seems easier to parse the sites into individual shapefiles (though that procedure is not discussed--but should be).
For either version, download the data for lab 3.
Arc GIS v 9.3
- Open ArcMap
- Add the lab data to the model. For 9.3 add the individual from## point files rather than the pooled from file. Note also that in order for the output of the iterator to be properly synchronized with the number of the points file from00.shp should be at the top of the TOC and from18.shp should be the last of the points in the TOC.
- Create a New Model
- Drag into the Model, the Viewshed tool.
- Drag in the crop DEM and connect it to the Viewshed Tool.
- Right Click on the Viewshed Tool and select make Variable>From Parameter>Input Point or Polyline Features
- Right click on the Input point or polyline feature >select Properties> Select the List of Values Radio Button and click OK. Notice the model change?
- Drag onto the Input point or polyline feature all of the from observer points.
- Double click on Viewshed Tool, and change the very last part of the output file name change "Viewshe_crop1" to "View%i%".
- Click on some other cell in the batch grid and then right click in the top cell, the one changed in the previous step, and select "Fill". This will apply the file name "View%i%" to each of the output rasters.
- Run the model
Arc GIS v 10
- Create a new Toolbox
- Inside this Toolbox, create a new Model
- Inside the model, drag in the viewshed tool. After this, drag in the input raster and connect it to the tool.
- From the modelbuilder window, right click and select Iterators>feature selection. Drag the input feature into the model and connect it to the iterator.
- Right click on the input feature (blue oval)> select Properties> click the radio button to make the object "A List of Values".
- Connect the Selected Features (green oval) to the Viewshed tool.
- At the end of the model, double click Output Raster (green ovals)> in the table that comes up add %n% to the name of the output raster.
Once you have calculated the individual viewsheds, figure out what it is for each site. Add these values to a table.
Make a new point file that is composed of 18 points. Determine how you will distribute the points and make this explicit. Run the iterate viewshed on the new points.Once you have run the individual viewsheds on the new points that you created, determine what is the difference in the viewsheds of the two sets of points?
IMPORTANT NOTE FOR ArcGIS 9.3 users: You will need to break up the points into individual shapefiles. To automate this process, use the Split Layer by Attribute tool.
Below is a YouTube clip that demonstrates the procedures under Arc v 10.
ESRI Geoprocessor Blog
ThisModelBuilder-Advanced Technologies video has some useful tips. It is over an hour long, but at about 15:00 minutes begins a discussion of viewshed analysis and iteration. In the demonstration,the viewshed model diagram did indicate the use of the list values option for the input feature. Setting the intput feature as a list seems to be the only way to get the model to iterate.