By Aileen Buckley, Mapping Center Lead
In our previous blog post, we introduced the ArcGIS Bump Map tools and described the structure of the model and how to run it. Now we want to talk about how you can symbolize the results and use additional tools to create stunning bump maps! The Bump Map Tools can be downloaded from the ArcGIS Resources-Model & Scripts page of Mapping Center. Symbolizing the results of bump mapping involves three steps – 1) symbolizing the hillshade, 2) symbolizing the elevation with a hypsometric tint, and 3) symbolizing the vegetation overlay with a layer tint or other color. Symbolizing the hillshade is fairly straightforward and we have discussed many options for how you can do this in previous blog entries, so we won’t go into that here. To symbolize the bumped surface, you have a number of options, so we do want to explore that in more detail. You have the potential to create a very realistic looking surface fairly easily!
In addition to the bump map surface, shown in figure 1 below…
Figure 1. The bump mapped hillshaded surface that is ready to be symbolized
…the ArcGIS Bump Map model also produces rasters that you can use to symbolize the output. The rasters represent the areas that were bumped for each type of vegetation. So you can use them to symbolize the bumps by using different colors for the different types of vegetation.
The rasters are created automatically by the Bump Map model and written to the ToolData directory. Look in there after you run the model and you will see rasters called vegpat0, vegpat1, etc…, where vegpat0 corresponds to the first set of parameters for the vegetation input, vegpat1 corresponds to the second, and so on. There is one vegpat raster for every input vegetation pattern that you specified.
In figure 2, each vegetation pattern is symbolized using a single hue. Conifers (vegpat0) are green and sedge (vegpat1) is brown.
Figure 2. Unique colors can be used to symbolize the different vegetation patterns
Alternatively, you can use color ramps to symbolize the vegetation, as in figure 3. Here the conifer pattern is symbolized using a green color ramp, and the sedge pattern is symbolized using a brown color ramp. Using the lighter color in the ramp for the higher values gives the impression that the tops of the bumps are illuminated and the lower areas are in more shadow.
Figure 3. Color ramps can also be used to symbolize the different types of vegetation
At this point you can display the hillshaded bump map along with the elevation surface using a hypsometric layer tint, and then overlay the vegetation pattern rasters with transparency to color the bumps (figure 4).
Figure 4. The colored vegetation rasters can be overlaid on the hypsometrically tinted elevation raster and the hillshaded bump map raster
The No Bumps Script
You can use the “No Bumps” script to create a raster that represents the elevation of the surface where there are no bumps. You can use this raster to apply the hypsometric tint for elevation values in the “unbumped” areas (figure 5). This will complement the colors you choose for the various vegetation classes. Both will then overlay the hillshaded bump map surface. The No Bumps script is included in the Bump Map Tools toolbox.
Figure 5. The output from the No Bumps script can be used with a hypsometric tint to represent the elevation of the surface
As we mentioned in our previous blog post, a ToolData directory and a Scratch directory are automatically created for you when you unzip the Bump Map Tools download from the ArcGIS Resources-Model & Scripts page of Mapping Center (figure 6).
Figure 6. The contents of the download
You will need to use these workspaces for the No Bumps script. Note — you must set the current workspace to the ToolData directory and the scratch workspace to the Scratch directory. Just make sure you navigate to or input these directory locations these when you run the script.
Once you run the No Bumps script, you can display all the rasters together to create a map of the elevation and the vegetation. In figure 7:
- the bump map raster is displayed on the bottom with no transparency,
- the no bumps script output is displayed on top of that using a hypsometric layer tint with 40% transparency,
- the conifer vegetation pattern is displayed on top of that using a single green color with 60% transparency,
- and the sedge vegetation pattern is displayed on top of that using a single brown color also with 60% transparency.
Figure 7. The vegetation rasters symbolized with single colors are then overlaid on the hypsometrically tinted No Bumps raster and the hillshaded bump map raster
You can see in figure 8, which uses color ramps rather than single colors to symbolize the vegetation rasters, that the result is truer to your input colors than if you did not use the output from the No Bumps script for the hypsometric tint (as in figure 4). This is because the bumped area would also be displayed with the underlying layer tint for elevation.
Figure 8. The vegetation rasters symbolized with color ramps are then overlaid on the hypsometrically tinted elevation No Bumps raster and the hillshaded bump map raster
Note that you can download some really great looking hypsometric layer tints from Mapping Center on the ArcGIS Resources > Styles page.
One last note, in order to improve the display performance in ArcMap, you might want to consider “flattening the rasters”. When you do this, you create one raster from all the rasters in the display. Then you can add that to your ArcMap document and remove all the others so you only have to display one raster image. Instructions for how to flatten the rasters are on the Mapping Center web site under the Flattening Overlaid Images description for the Crater Lake map.