Using Arc2Earth to Create 3D Google Earth Displays with ArcGIS Data
As I’ve mentioned in previous posts on Arc2Earth, one of my favorite functions is the ability to create 3D Google Earth displays using existing ArcGIS data. The ability to visualize your ArcGIS data in a 3D display makes for stunning visualizations, but it can also help reveal and emphasize patterns in your data. For example, in a previous post I described how we used a combination of ArcGIS Desktop along with the Spatial Analyst extension, Arc2Earth, and Google Earth to analyze crime patterns in Houston, Texas through the use of heat-maps and 3D display of various crime categories.
In this post we’re going to explore how you can use Arc2Earth to export your ArcGIS data as 3D extrusions. One of the most visually appealing options in Arc2Earth is the ability to create 3D Google Earth extrusions from your ArcGIS data. Clicking the Extrude Options button on the Layer tab brings up the Layer Extrude dialog which allows you to extrude a layer based on attribute values in your feature class, set specific values for all features, or use existing Z values of a layer.
Let’s take a closer look at the Layer Extrude dialog which is used to display vector data in three dimensions inside the Google Earth viewer. The Altitude Mode options allows you to set a value of absolute (based on sea level), relative (based on the current terrain level) which is the default, or clamped which is based on the current terrain level but clamped to the ground. In addition, you can extrude based on a number of options including Z values of a layer (if available), attribute values in a field (must be a numeric field), or a set value in meters for each feature. The visibility of extrusion walls can also be controlled through the “Show extrusion walls” checkbox. Finally, extrusion height can be calculated based on a percentage of all field values in relation to a minimum and maximum height in meters.
Now let’s examine the various options for performing 3D extrusion in Arc2Earth. As previously mentioned, you can extrude based on a number of options including Z values of a layer, attribute values in a field, or a set value in meters for each feature. Some ArcGIS layers already have valid Z values associated with their geometry data and are said to be “Z Aware”. In these cases it is possible to use the Z values associated with each feature as the value which will be extruded. Other methods of extrusion include the capability of extruding based on tabular attribute data for the layer. This uses numeric attribute fields to determine the height of extrusion. All data in this case is assumed to be in meters although feet can be selected as well. In addition, you can use the “Calculate Extrude height…..” check box to use a percentage of the min and max you enter to derive the extrude value. Finally, you can extrude each feature by a set value which you enter. This value is calculated in meters.
For more information about Arc2Earth please see our e-learning course “Arc2Earth for ArcGIS Users“.