What Is A Canopy Height Model (CHM)
Canopy Height Model: What It Is and Why It’s Important In Forestry
A 3D virtualization of a LiDAR Canopy Height Model of a Forest.
Have you ever wondered how Canopy Height Models (CHMs) help us measure forest growth from above? CHM’s are a powerful post processing tool that we use after mapping forests with our LiDAR systems. Once accurately processed, CHMs help us to deliver precise, actionable data for forestry management. Let’s explore why this powerful tool is a game-changer for anyone working in forestry.
What Is a Canopy Height Model (CHM)?
In Forestry, a Canopy Height Model is a 3D representation of the height of vegetation in a forest, calculated by subtracting the ground elevation (Digital Terrain Model) from the top surface of the canopy (Digital Surface Model), allowing us to understand the forest's vertical structure and overall health. In simpler terms, it’s a map that shows how tall the trees are.
The Difference Between Elevation DSM Map and CHM Map.
A DSM Elevation Map takes the elevation of the lidar point returns from the tree canopy, and displays the actual elevations (think above mean sea level) in meters, not taking into account ground elevation or ground points.
This is different than the CHM as I explained, which is the height difference between ground and the canopy.
As you can see in the images below, the DSM is on the top and the CHM is on the bottom. The trees in the DSM that look very tall compared to the other trees are really just higher in MSL elevation due to the terrain elevation changes. You can compare these to the Digital Terrain Model DTM below to see what I mean. Want to build your log cabin at the highest elevation on your property and not have to cut down the tallest trees? That’s where using both the DSM and CHM come in super useful. Very cool right?
Drone LiDAR Forestry - Digital Elevation Model DEM/ Digital Surface Model DSM
Drone LiDAR Forestry - Canopy Height Model CHM
Why Are CHMs Important?
CHMs provide insights that go beyond basic forestry aerial imagery. Here are some of the ways they’re used:
Forest Inventory: Easily measure tree heights and canopy density to estimate timber volume.
Wildlife Habitat Analysis: Understand the vertical structure of a forest to assess habitats for various species.
Reforestation Monitoring: Track tree growth over time to evaluate the success of reforestation projects.
Risk Assessment: Identify potential wildfire hazards by analyzing vegetation density and height.
Carbon Stock Estimation: Estimate the biomass of forests for carbon credit calculations.
How To Make a Canopy Height Model
Here’s a quick rundown of how we generate CHMs using drones and LiDAR software like LiDAR360 and Global Mapper:
Data Collection: We fly our drone and LiDAR payload according to the specs and resolution requirements of the deliverables.
Ground Elevation Mapping: We create a Digital Terrain Model (DEM/DTM) by classifying the lidar ground points.
Canopy Mapping: We generate a Digital Surface Model (DSM) to map the top of the forest canopy.
CHM Calculation: The DTM is subtracted from the DSM to produce the Canopy Height Model.
Analysis and Reporting: The CHM is analyzed and delivered as an easy-to-use map or dataset.
Key Features of Our CHMs
High Resolution: Capture even the smallest details with centimeter-level precision.
Customizable Outputs: From 3D visualizations to contour maps, we provide formats that suit your needs.
Scalable Coverage: Analyze anything from small conservation plots to vast commercial forests.
Real-World Applications of CHMs
Our clients use CHMs for a variety of purposes:
Timber Management: Maximize yield with accurate height and volume measurements.
Wildlife Studies: Map habitats to support biodiversity conservation.
Urban Forestry: Monitor tree health and growth in urban environments.
Disaster Recovery: Assess damage after storms or wildfires to prioritize recovery efforts.
Let’s Work Together
CHMs are just one of the many tools of our Forestry Drone Services we use to help you manage forests smarter and more sustainably. With our precision-driven approach, you’ll gain valuable insights to make informed decisions that positively impact forest ecosystems. Ready to see the difference a Canopy Height Model can make for your project? Contact us today, and let’s talk about how we can work together to achieve your goals.