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Introducing the Ground Control Point interface

Sure, your drone can take videos and photos from above, but while you’re taking those photos why not turn them into something mappy?

OpenDroneMap is an open source toolkit that can help you do that. It takes aerial imagery such as that created with your drone and turns it into several other types of data, such as point clouds, meshes, and orthophotos.

Example of a point cloud created with OpenDroneMap. Via

In order to make its output more accurate, OpenDroneMap needs to know which part of earth the images from your drone represent. And if your camera doesn’t automatically do this you have to manually associate points on the earth with points in your imagery. These points are called ground control points (GCPs), and the files are a little difficult to write by hand:

An example of a ground control point (GCP) file.

Over the past few years, Stamen has worked with Cleveland Metroparks to create a webapp that generates this file for you, and we call it the Ground Control Point interface (GCPi). This tool can be used independently or in conjunction with OpenDroneMap, and it allows you to create and edit files that OpenDroneMap can use to process images from a drone.

The interface is relatively straightforward. You drop in a set of images and optionally a GCP file, then you add points to the images and connect them to points in the appropriate places on the map. Points on the map can be associated with multiple points from images.

Once you’re done, you can export the GCP file in a format that will work with OpenDroneMap. If you notice a mistake in your file, you can easily load the file and your images in GCPi and update the file.

Stamen created GCPi and recently made a number of improvements to it. These included a variety of user interface and design updates, exporting GCP files using different projections, and labeling GCPs.

Finally, you can also use GCPi through WebODM, an interface to OpenDroneMap that uses a webapp to connect to OpenDroneMap:

If you’re curious to learn more about how you could use these open source tools to make an array of impressive imagery and data, we encourage you to visit OpenDroneMap.

Stamen been exploring open source and cartography with our clients for many years; if you have a similar project you’d like to collaborate on, get in touch with us!

Published: 06.28.18
Updated: 05.22.23

About Stamen

Stamen is a globally recognized strategic design partner and one of the most established cartography and data visualization studios in the industry. For over two decades, Stamen has been helping industry giants, universities, and civic-minded organizations alike bring their ideas to life through designing and storytelling with data. We specialize in translating raw data into interactive visuals that inform, inspire and incite action. At the heart of this is our commitment to research and ensuring we understand the challenges we face. We embrace ambiguity, we thrive in data, and we exist to build tools that educate and inspire our audiences to act.