July 1, 2025
How to Create a Contour Map
My hiking checklist always includes earbuds, snacks, bug spray, and hiking boots, but I don’t always bring the same sized bag. On longer hikes, I use a backpack with plenty of hydration and food, while for easy walks I just bring my belt bag. During my adventure planning, it is important to consider not only the length, but the elevation change that will occur to determine what I need to bring, and therefore which bag. I always prefer a contour map that represents how steep the terrain will be so I can understand how many breaks and Gatorade® I will need.
What is a Contour Map?
Contour maps, also known as topographic maps, represent the elevation of the land’s surface using lines. These contour lines delineate changes in elevation. Various lines are spaced out at predetermined intervals, with each line connecting points of the same height and representing a constant elevation. In the example below, the contour interval is 100. Every line shows that the elevation has changed by 100 feet. In flatter areas, the contours are visually much further apart; however, in steep regions where the elevation changes rapidly, the lines are very close together.
These maps provide an illustration of the terrain from a 2D perspective. Hiking trail maps are some of the most common examples of contour maps, showing how much and how fast the land’s elevation changes. Topographic maps are also valuable for planning infrastructure such as roads and bridges, agriculture, and preparing for natural disasters.
How to Generate Contour Lines
Whether you are mapping out a new trail, planning a new all-inclusive resort, or building new roads, Global Mapper® can create contours from elevation data in a few steps. In this example, I will analyze Maine’s tallest mountain: Mount Katahdin.
Starting Terrain
In Global Mapper, contours can be generated from any loaded elevation data, including grids, point clouds, and vector features with an elevation attribute. A Global Mapper Pro® license is required to generate contours directly from a point cloud. Pro users can also generate contours or digital terrain models from lidar.
In this example, I have an elevation grid from the USGS loaded in Global Mapper. The Create Contours tool will open up a dialog box for the generation of the lines.
Contour Interval
After naming the contour layer, you are able to customize the line weight, frequency, and units of the contours. Contour Interval indicates the elevation change a line will represent. For Mt. Katahdin, I set the interval to 100 feet; every contour represents that the elevation has changed by 100 ft.
The Contour Interval Multiplier setting is also known as index contours. This applies feature classes to the different line categories and determines which contours appear bolded. In this situation, every 5 contours will be bolder, and every 10 will be boldest.
If I were to check the “Only Generate Contour Lines at a Specified Height”, contour lines will only be created at the elevation set in the contour interval. In other words, a specified height of 3000 with the box checked would only create lines at 3000ft.
Range & Resolution
Further customize your contour map with additional settings further down in the dialog box. You can set the elevation range for contour lines to be generated. The default heights are the range of the loaded data, but if I were only looking for contours to be generated for the steeper parts of Katahdin, I could adjust the minimum to 3000ft.
Resolution can also be adjusted to create more or less detailed contour lines. Larger resolutions will create less detailed, smoother lines that take up less space. For most maps, the default can be kept the same.
Additional Options
There are a series of additional check boxes within the dialog box, such as interpolating small gaps or exporting contours directly to a package file. Here are a few boxes that I like to check.
- Appended Unit Labels to Elevations: Since my legend is in feet, I want to make sure that the contour labels display that unit.
- Smooth Contour Lines: Checking this box will improve the appearance of the contour lines, making them less jagged.
- Discard Closed Contour Lines Shorter than: By denoting a length and checking this box, short closed loops will not be generated, creating a cleaner topographic map.
Simplification
The Simplification tab allows users to determine if points contribute to the shape of a contour. More simplification will result in fewer points, creating a smaller file but a more jagged, less accurate contour line. Less will keep more vertices, resulting in smoother lines and a larger, more accurate file.
Tiling
If you are processing a really large point cloud, you can break up the contour generation to create smaller files and help reduce the memory requirements of your computer. If enabled, Global Mapper will break the data into a grid and create contours tile by tile, instead of trying to tackle the entire map at once.
Contour Bounds
Similar to setting the elevation range, you can also determine what parts of the data to create contours of by setting bounds. These bounds can be all visible data on screen, the option to draw a box, or crop to a selected area feature.
When processing my small Katahdin elevation grid, I have left all of these tabs at their default settings.
It is safe to say that for climbing Katahdin I will need to bring at least a backpack. Explore how to use Global Mapper to complete your project today by downloading a free 14-day trial!
