What Lidar Can and Cannot Tell Us About Your Forest

By Jennifer Hunt (Content Writer), Scott Hillard (Biometrician), and Will Woodroof (Technical Services Manager)

What Lidar Can and Cannot Tell Us About Your Forest

Technology is changing how foresters and land managers see forests. Two frequently used technologies, Lidar and imagery (multispectral air and satellite), give us tools to support management decisions, but they are no replacement for a boots-on-the-ground approach. Coupled with the localized experience of an AFM forester, Lidar is a powerful tool to give landowners information and data about their forest. In this blog post, we’ll cover what Lidar and imagery do well, opportunities and misconceptions, and why a local forestry expert is still your best partner in forest and land management.

What are Imagery and Lidar?

Imagery helps us gather information about the land from a distance. This is accomplished through drones, satellite imagery, and aerial photos. Lidar is an acronym that stands for Light Detection and Ranging. It’s simply a sensor that sends a pulse of light from the device and detects its reflection. When these pulses of light hit the trees (and ground) and bounce back, the return time tells us the distance between the object and the sensor. When normalized to the ground, a highly detailed 3D model of the forest and the ground beneath it can reliably give us information about forest structure and terrain.

What information can we glean from Lidar?

Lidar is good at measuring forest structure, including tree height (individual trees and averages), canopy density and layering (low, mid, and upper canopy), crown size and shape, and ground elevation and slope (even under dense trees). This information allows foresters to create terrain maps, contours, and hillshades, as well as visualize the property in ways that traditional maps cannot. It’s important to note that Lidar does not create direct measurements but rather estimations, but these estimations are very accurate when calibrated with field measurements and data. Lidar can strengthen existing on-the-ground inventories and allow biometricians and GIS analysts to reliably estimate tree height, basal area, volume, biomass, and trees per acre. With all of this information at our fingertips, we’re able to make real-world management decisions.

How do foresters and biometricians use Lidar and imagery in practice?

LiDAR and remote sensing support numerous aspects of planning and operations, including harvest planning, road and access layout, identifying steep or sensitive areas, and stand boundary delineation. But that’s not all—we can also use these technologies to identify areas of concern and opportunity in a forest, including:

• Forest health, including invasive species identification (imagery)
• Stream management and boundary line mapping (Lidar)
• Volume estimates and site suitability analysis (imagery and Lidar)
• Conservation management, biodiversity, and flora and fauna habitat management (Lidar and imagery)

All of this information helps us flag areas of higher and lower volume, changes to forest structure, and potential problem areas that may need closer inspection. This allows us to track changes in vegetation health over seasons or years.

What are some misconceptions and limitations of Lidar and imagery?

As with many technologies, its capabilities have been overpromised but underdelivered. Initially, people viewed Lidar as a tool to replace, rather than support, measurement. Certain subjective elements, like Tree Quality Index (TQI), are hard for remote sensing to assess, but foresters can observe a tree and evaluate the sweep, crook, and forking, and make a judgment call. Similarly, remote sensing and Lidar can struggle to distinguish tree species with similar characteristics, like the loblolly pine and Virginia pine. Likewise, live and dead tree assessments are easily determined by foresters, but can be difficult to assess via Lidar.

While these technologies provide excellent support for in-field data collection and post-collection analysis, their biggest constraint is time and budgetary constraints. The data itself should provide the means to answer almost any question since having a digital twin is now possible, but acquisition costs are high, and a technical skillset is needed to process and understand the data. While the technology is maturing, it still requires a forester to make judgment calls.

What is the future of LiDAR and imagery? 

As forest technology continues to grow and evolve, there are a few advancements that show progress. Terrestrial Lidar shows promise, and improved analysis methods (like Bayesian approaches, that is, using probability analysis that combines new observations and prior knowledge), which may unlock deeper insights. As this technology continues to mature, it will complement, not replace, foresters, as subjective assessments will remain a crucial aspect of forestry.

Lidar and imagery analysis can provide powerful insight into forest structure and terrain. The most effective land management blends technology, experience, and on-the-ground knowledge. When used together, remote sensing technologies and field expertise help landowners make smarter, more confident decisions about their forests.