001] How to Create a DEM from Contour SHP Files in Global Mapper
Import digital topographic maps and generate a high-resolution 3D terrain grid using elevation attributes.
This session introduces the fundamental GIS workflow for landscape and urban analysis. You will learn how to import SHP files (even within ZIP archives), identify and map elevation attributes such as "CONT," and configure grid spacing settings to generate a professional Digital Elevation Model (DEM) for 3D visualization.
Download and Install Global Mapper Trial Version
First, you'll need to download the trial version.
If you visit the Blue Marble Geographics website, you will see a menu for a "Start Free Trial." Please note that personal emails (Naver, Gmail, etc.) are generally not accepted; you must use an email associated with a company or an educational institution. Once your email is confirmed, download and install the software before proceeding with the content below.
As you follow along, try comparing the workflow with other GIS software. This is the "highlight" of using Global Mapper.
▲ Check out the step-by-step video tutorial for creating DEMs!
Importing Digital Topographic SHP Files
Now, let's begin creating a DEM.
One of the greatest advantages of Global Mapper is its ability to import an incredibly wide range of file formats.
Loading ZIP-Based SHP Files Directly
We will import a continuous digital topographic map in SHP format downloaded from the National Spatial Data Infrastructure portal. When downloaded, these maps are typically saved as a single ZIP file. Global Mapper is smart enough to load the data even if it is still compressed in a ZIP folder.
The result of the import is as follows:
Understanding Imported Contour and Elevation Layers
Checking Elevation Attributes in Contour Data
To create a DEM, you need to know which attribute in the digital map contains the height values. Select the Digitizer Tool (the pencil icon) from the top menu and double-click on a contour line.
Using the Digitizer Tool to Inspect Attributes
The value belonging to the CONT attribute represents the elevation figure. Once you've confirmed that the contour layer uses "CONT" for elevation, close the window.
Now, select the layer in the Control Center, right-click, and select Options.
Assigning the CONT Attribute as Elevation Data
In the options window that appears:
Go to the Elevations tab and select "CONT" from the "Get Elevations From Attribute Value" list box, then click Apply. This tells Global Mapper to recognize the "CONT" value as the elevation data.
Creating a DEM Grid from Contour Lines
Now it's time to generate the DEM Grid. Right-click on the selected layer and choose Analysis -> Grid.
Opening the Grid Creation Tool
Select the layers you want to use for the DEM and click OK. The Grid Creation Options window will appear.
Setting Grid Spacing for DEM Generation
The grid spacing determines the horizontal resolution of your output DEM. While it varies depending on the site size, for a radius of about 1km, I typically set the Grid Spacing to Use to 5 meters.
Choosing the right spacing is a trade-off between detail and performance. A tighter grid spacing (e.g., 1 or 2 meters) will capture micro-topography and sharp ridge lines more accurately, which is crucial for detailed architectural site planning. However, for regional watershed analysis or vast coastal mapping, a larger grid spacing is highly recommended to prevent Global Mapper from consuming excessive system memory and slowing down rendering speeds.
Defining DEM Grid Bounds
Next, switch to the Grid Bounds tab to restrict the analysis area. By default, Global Mapper will attempt to process the entire bounding box of all loaded data.
If you select All Loaded Data, the software will convert every single contour line available into the grid. However, to save processing time and keep your workspace clean, using the Draw a Box option is highly efficient. This tool allows you to visually click and drag a temporary bounding box directly over your target project site, ignoring unnecessary peripheral terrain data and instantly flattening the processing queue.
Here you can set the area for the DEM generation. All Loaded Data is used to convert the entire selected layer into a DEM. By choosing Draw a Box, you can select only a specific rectangular area.
Click and drag the mouse to define the appropriate area, then click OK. The selected area will now be indicated on the main screen.
Click OK to proceed. The DEM is now created!
Viewing the DEM in 3D
A 3D screen that you can rotate and inspect will appear. The process is complete!
Final Thoughts on DEM Creation in Global Mapper
I've only explained the very basics for now, despite the many options and functions available for DEM generation. I will explain the details as needed as we move forward with the lectures.
That's all for today~
- Learn previous workflow in Global Mapper Lesson Index
- Continue learning with [003] How to Create DEMs and Perform Terrain Analysis in Global Mapper
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