How to use Global Mapper’s Raster Reclassify tool

Written by Jeff Hatzel, Senior Application Specialist

With the release of Global Mapper v21.1 comes the addition of an exciting new tool, Raster Reclassify. The development of this tool, like so many in Global Mapper®, was heavily driven by requests from our users. The initial release of this tool allows users to modify the pixel values of a palette image. A common use case for this might be to adjust the classes with a landcover file to create a new layer with a simplified set of classes. Let’s look at a more advanced workflow: using Raster Reclassify to adjust the values of an image created from classified lidar.

Hint: If you’d like to learn about this tool in detail, review the Raster Reclassify Knowledge Base page!

Using Lidar Classification Codes to Make a Raster Layer:

If you’re familiar with the Create Elevation Grid tool in Global Mapper, you know that this tool allows you to create a terrain layer based on the elevations within the source point cloud. You may also know that when working with lidar data, this tool allows you to create a grid-based on a variety of lidar attributes and properties, for example, classifications.

Classified lidar data
Classified lidar data (left) was gridded based on its classification code to make an output raster (right).

This resulting file represents multiple lidar classes from the source point cloud. The classes follow the same color scheme used to display lidar by classification. However, it’s possible we may only have an interest in a specific set of classes or an individual class, buildings for example. We’ll address that with Raster Reclassify.

Hint: Take a look at the different Grid Type options in the Create Elevation Grid tool.

Raster Reclassify to Highlight Classes of Interest:

The Raster Reclassify tool (part of the Analysis Menu) allows you to adjust the values of the source layer. In this situation, we want to focus on buildings. We’re going to merge all non-building classes: ground, low, medium, and high vegetation, bridges, powerlines, and water. Buildings will be retained as a unique class.

Raster Reclassify
Raster Reclassify allows you to load the source palette from a reference file. You can choose which classes you want to reclassify, adjusting their description, color, etc.

This tool creates a new output layer within the current Global Mapper workspace. As you can see below, that layer will now only show the newly created classes you outline in the Raster Classification Rules section of the Raster Reclassify tool.

Source file comparison
The source file (left) compared to the reclassified layer (right). The reclassified layer now only shows two classes, based on the rules set in the Raster Reclassify tool.

Hint: Want to display different layers side-by-side in the same workspace as we’ve done in some of the above images? Check out Multiple 2D Map Views!

What’s Next?

Products created by Raster Reclassify can be used in a variety of applications. Some may be final deliverables for reclassified landcover datasets, used to make or adjust clutter grid files, or any other number of possibilities.

How will you use the Raster Reclassify tool?

Keep an eye out in the future for new functionality in this tool, including the ability to reclassify terrain data and non-palette imagery!

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