Using drone mapping as a way to create beautiful maps and 3D models of our study sites is pretty cool. Those photogrammetry outputs are certainly useful, but in my experience they are often only the starting point of truly awesome monitoring power. The real power of drone photogrammetry emerges when surveys are repeated over time. Comparing digital twins of a study site is incomprehensively potent technology that we have available to us in the modern age. And it is critical that we use it more. In order to do this, we need to understand what this technology actually does, what it means and how to use it.

https://www.youtube.com/shorts/jDsehHr-Vgw

By flying the same area months or years apart, we can generate 3D point clouds representing the landscape at different moments in time. These point clouds can then be aligned and compared using open-source software such as CloudCompare. One particularly powerful tool is M3C2 (Multiscale Model to Model Cloud Comparison), which measures how much the landscape has changed between surveys.

The result is not only a visual map showing where change has occurred, but also a statistical record of how much change has taken place.

One output that I find especially valuable is the histogram generated from the change analysis. While summary statistics such as the mean and standard deviation tell us the average change and overall variability, the histogram reveals how that change is distributed across the landscape.

In a recent fynbos recovery project, the histogram showed that most vegetation growth was relatively modest, while a much smaller number of plants experienced substantially greater growth. Without the histogram, we would know there was variation. With the histogram, we could see where that variation was coming from.

In this short video, I use a simple plant-growth example to explain mean, standard deviation, and histogram interpretation before applying the concepts to a real drone-derived point cloud comparison.

For those involved in conservation monitoring, restoration ecology, or long-term ecosystem assessment, I believe one of the most overlooked strengths of drone photogrammetry is not the map itself, but the ability to create a measurable, repeatable record of environmental change through time.

https://wildlabs.net/en/inventory/organisations/geowing-academy