Easily Created Slope Maps in Global Mapper
Creating slope maps in Global Mapper can be as easy as changing a dropdown menu setting. Slope maps are often used in planning construction, trails, and more. They display the change in elevation of an area. Topographic maps use contour lines to communicate a similar idea, but a slope map displays slope values as a grid layer based on degrees or percent slope.
Slope maps in Global Mapper are made using elevation rasters. Are you creating a slope map from Contour lines? Grid it into a raster first using the Create Elevation Grid tool.
In Global Mapper, the display of elevation data can be used to communicate elevation values as well as slope values. To see the slope values in an elevation raster or grid layer, simply change the shader dropdown menu in the Analysis toolbar. Global Mapper will automatically calculate and display the slope value for each grid cell.
Another built-in shader option is the Slope Direction Shader which displays the aspect of each slope in degrees. These screenshots were taken of the same data in the same location, however, they communicate different information about the terrain. The colors of the slope direction shader can be changed in the Configuration Menu under Shader Options.
By default, the Slope Shader legend in the workspace displays the slope in black and white, and the listed minimum and maximum values are 2 standard deviations away from the mean. This means that the values listed at the top and bottom of the legend don’t necessarily include distant outliers, although they are still displayed on the map.
You can adjust the slope shader to use specific min/max values. All other values will be colored white. The Coloring Between Min and Max Slope Values option provides the ability to add a third color to the gradient in between the black and white. This is one method for visually highlighting the min/max values, though creating a custom shader provides more flexibility.
Custom Shaders in Global Mapper allow you to choose which values, or ranges of values, are assigned a color. You can color specific values while leaving the others as white, or create a gradient of values, as shown in the image below. In this example, the slope values are displayed 5 degrees apart in a gradient, highlighting the steepest slopes with the brightest color. Shadows are applied indiscriminately to the elevation layer as a whole based on settings in the hill shade tool.
For step-by-step instructions on creating an elevation shader, check out this tutorial: How to Create a Custom Shader. When creating a slope shader be sure to check the box at the bottom of the dialog Shade Slope Values (Degrees) Rather than Elevations. This will change the provided values so they are treated as slope angles in degrees and allow you to setup shading based on the slope.
Learn more about all of Global Mapper’s shaders in this blog: Custom Shaders for Gridded Data in Global Mapper.
For some workflows, area features are necessary to outline areas of desired slope. The Vectorize Raster tool can be used to automatically create these area features. With the Slope Shader enabled in the workspace, the tool will automatically adjust to measure slope values instead of elevation.
To extract multiple values at once, First use the Raster Reclassify tool to break up the layer into sections based on slope. For a full demonstration of how to use both of these tools to create polygons, see this video tutorial: Extracting slopes in Global Mapper
Interested in changing the slopes in your data? Here is a selection of tools in Global Mapper that manipulate slopes in data: