Visualizing Terrain in ArcGIS Pro

This tutorial covers a variety of ways of visualizing terrain via digital elevation models (DEM) using ArcGIS Pro.

Digital Elevation Models

Traditionally, there have been two data models that have been used to represent the surface of the earth as geospatial data: the vector model and the raster model. They are referred to as models because they are abstract simplifications of the world that can be useful for analysis and visualization.

Vector data stores locations as discrete geometric objects: points, lines or polygons.

Examples of Points, Lines and Polygons To Model Features in Denver, CO (Base Map From OpenStreetMap)

The raster model represents the world as rows and columns of evenly spaced pixels. The raster model is most useful for representing characteristics of areas that do not have clear boundaries, such as vegetation or other environmental features.

Raster Satellite Imagery of Denver (Google)

Raster data can be converted to vector data, and vice versa, but the conversion are imprecise and can introduce inaccuracies.

Points vs Lines vs Polygons

One common use for the raster model is elevation data, which is the height of an area above some reference surface, such as mean sea level, or a geoid. While terrain can be stored as vectors (triangular irregular networks or TIN), rasters are a simple, effective way to store the irregular physical features of an area of land (terrain).

Digital elevation models (DEMs) are raster data sets containing rows and columns of pixels, where each pixel represents the elevations at a specific location on the surface of the earth. Elevation data is useful in a variety of fields like geology, hydrology, biology, civil engineering, urban planning, transportation, and disaster management.

Acquiring DEM Data

One elevation dataset made freely available to the general public by the federal US Geological Survey is the Shuttle Radar Topography Mission (SRTM). This was data gathered by instruments flown on the US space shuttle Endeavour on February 11 - 22, 2000, and covers almost the entire globe.

The SRTM Hardware On Endeavour (NASA JPL)

Remotely sensed data from satellites is often divided into scenes that cover specific areas and can be easily managed. Scenes from the USGS are made available in a number of formats. The GeoTIFF (tagged interface file format) is commonly used and works with a variety of different software, including ArcGIS Pro.

SRTM scenes can be downloaded from the US Geological Survey's EarthExplorer web site.

In order to download data, you need to register (for free). Click the Login button and select

Registering On USGS Earth Explorer

Once you have registered, you can log in and download SRTM data for specific areas. This example uses a scene around Chicago, IL.

  1. Log in
  2. Search for a location with the city name and state.
  3. Click Data Sets
  4. Select Digital Elevation -> SRTM -> SRTM Void Filled
  5. Click Results
  6. If you have multiple results, click the Show Browse Overlay icon by each result to find the scene that best covers your area of interest.
  7. If you have a choice between one and three arc-second options, 1-ARC is higher resolution.
  8. Click the download icon.
  9. Select the GeoTIFF download format. This request may take a few minutes to process.
  10. When the file is available, chose the option to Save it.
  11. In the Windows Explorer, view your downloads directory. The download may take a minute or more, so wait until the temporary .part file goes away before proceeding.
Downloading a SRTM DEM via USGS Earth Explorer

Metadata gives information about a geospatial data set such as the date represented and the dimensions of the area covered. To view the metadata for a scene, click the metadata icon.

Viewing EarthExplorer Metadata

Adding DEM Data To a Project

  1. Create a new project and give it a meaningful name.
  2. Add Data to your map with the GeoTIFF file.
  3. When asked to Build pyramids, this is optional. Pyramids are an internal representation of the raster data that can improve the responsiveness of the software when working with large data sets. It mayl take up to a minute to complete this operation.
  4. The SRTM data is in unpojected WGS 1984 format, which stretches areas in North America to appear wider than they are. Change projection to appropriate state plane coordinate system or to WGS 1984 Web Mercator if you anticipate using this data in a web map.
Adding DEM Data To a Project

Visualization Types

False Color

By default, raster data is initially visualized as grayscale, which is a useful, largely neutral way to look at the data. However, to present the data to readers, a false color symbology can make the visualization more descriptive and appealing. As with all maps, caution should be used in presentation since false color can exaggerate or create a misimpression of what is actually on the ground.

ArcGIS Pro has a variety of color schemes designed for elevation. This video shows a how to create a false color visualization with a layout for a map figure in a document.

Creating a False Color DEM Visualization: Chicago, IL

Hillshade

Another common way of visualizing terrain elevations is with hillshading, which shows areas of brightness and darkness as if the terrain were lit from the side.

Hillshading is most dramatic when there are hills to shade. Because the terrain around the example area of Chicago used above is fairly flat and heavily urbanized with low buildings, hillshading is not particularly interesting.

Uninteresting Hillshading Around Chicago, IL

Therefore, this example uses a mountainous area around Lake Champlain in northeast New York State.

  1. Create a duplicate map if you want to preserve existing symbology.
  2. Under Analysis, open the Tools.
  3. The Input raster is the DEM you will be hillshading.
  4. You can probably just use the default Output raster, which will be placed in the project geodatabase.
  5. The default hillshade will be visualized grayscale. You can change the symbology to a false color scheme to add visual interest.
Creating a Hillshade Map From a DEM: Lake Champlain, Upstate New York

Contour Lines

One classical way of visualizing elevation on two-dimensional maps is the use of contour lines that denote locations where the elevation crosses given intervals of elevation, such as 100 feet, 200 feet, 300 feet. In that example, the interval between contour lines is 100 feet.

Topographic maps with contour lines are used by civil engineers and planners when designing structures and communities. They are also used by hikers to plan routes.

The Contour tool in ArcGIS Pro allows you to create contour lines.

  1. Create a duplicate map if you want to preserve existing symbology.
  2. Under Analysis open the Tools and search for the Contour tool.
  3. The Input Raster should be your DEM.
  4. The Output Feature Class is where the contour lines will be placed. Leaving the default name and changing it later is probably the safest choice.
  5. The Contour Interval will depend on how varied the topography is in your raster, what you are going to be using the contour lines for, and how close you want the contour lines to be to each other. You may need to make multiple attempts to find a number that gives contour lines that are not too dense to read, but not too sparse to be useful. This example in this mountainous area uses 100 meter contour interval.
  6. Run the tool.
  7. You may want to hide the DEM layer and style contour lines over a lightly-colored labeled base map so the reader can clearly identify the lines.
  8. Add labels.
Creating a Contour Line Map From a DEM: Lake Champlain, Upstate New York

Contour lines are commonly used on topographical maps, such as those that have been produced by the US Geological Survey since the late 19th century. The layout of professional-quality topographical maps is a complex art that requires significant labor. If you need a topographical map as the base map for a thematic map, the USA Topo Maps base map will save you alot of time.

Using the Topographical Base Map

Scene

ArcGIS Pro can create perspective views (3-D scenes) of terrain elevation.

  1. On the View tab, select Convert to Local Scene. Global scenes are for large areas as if viewed from space. Local scenes are for small areas as if viewed from an airplane.
  2. Right click on the elevation layer and select Zoom to Layer, which should center the DEM in the display window.
  3. In the Contents pane, right-click on Elevation Surfaces and Add Elevation Surface with your downloaded DEM GeoTIFF.
  4. Unselect the WorldElevatio3D/Terrain3D elevation surface since you will use the DEM as your surface.
  5. In the Elevation Surface tab, change Vertical Exaggeration to 5. The choice of what number to use here will depend on now much topographical variation is in your data and how much you want to exaggerate that variation to make it more prominent.
  6. Click the middle mouse wheel and drag to change the altitude and direction of view.
Creating a Perspective Scene With a DEM

Save Your Project

When you are finished with the project for the day, you should save a project package containing your work to ArcGIS Online. Your imported raster data will be saved with the package.

Saving a Project Package