Drones for Forestry
Recently I have had a few discussions with colleagues regarding the use of drones for forestry related applications. For some uses the business case is obvious and compelling. However, in many cases the value of a drone is not obvious with current measurement and management systems. Below I will share some of what we discussed.
I would describe the use of drones as “on demand” remote sensing at a “tactical” scale. By “tactical” I mean the size of a harvest unit – perhaps five to 100 hectares. The remotely sensed data can include:
- Live streamed video.
- High resolution colour photography.
- Infrared imagery
- Thermal Imagery
- LiDAR (Light Distance and Ranging)
I thought it best to divide this discussion into bite sized chunks, the first being Silviculture.
Silviculture –management activities from regeneration to ready for harvest.
I was surprised to learn about drones designed to replace tree planters. The company pursuing this innovate application is Drone Seed. They are also able to perform spot treatments of herbicide. The use of drones for these applications will improve worker safety, as they will no longer have to leave the road!
The acquisition of remotely sensed data will provide the following benefits:
- Video live feeds will allow forest managers to determine which sites need further examination. This may be on foot or with the drone. This will save time when conducting the assessment. However, the more significant savings is as a result of better decisions and consequently more effective treatments.
- Normalized difference vegetation index (NDVI) imagery can be used as a means of determining photosynthetic activity. This can provide an excellent tool to assess the health and vigour of the forest.
- Colour imagery may be processed to provide a two or three-dimensional image of the forest. This can then be used to measure forest attributes of interest and guide management decisions. I believe that to really take advantage of this imagery 3D models should be created from the imagery. This will allow different measures to be applied. For example, instead determining trees per hectare we could instead determine the proportion of the growing space lost to gaps and non-commercial species.
- An assessment of fuel loading post harvest could aid in planning wildfire risk management and mitigation activities.
- In the event of wildfire, thermal imagery can help with suppression activities.
- Monitoring of timber theft and vandalism. Regular over-flights will help to deter these illegal activities.
- A variety of environmental risks can be monitored with remotely sensed data. This will allow timely response to issues.
Forest Inventory and Planning
Considerable value can be added to a forest estate with better data. Knowledge of the current growth rate of forest stands can help determine the optimal timing of the harvest for specific areas. It is likely that this is where data captured by satellite or manned aircraft can be combined with timely updates provided by drones.
For example, LiDAR data captured five years ago provides a reliable inventory of the entire forest estate. The data associated with units planned for harvesting in the next five years can be updated with drones. Planned Harvest Units with higher growth rates can be deferred to allow more value to be captured while units with lower current growth rates can be harvested first.
The most significant benefit of drones for a forest land owner may be the use of drones to facilitate the management of harvesting activities. Some of these benefits could include:
- Use LiDAR derived terrain model to plan road locations. Upon completion of road construction, use data acquired to determine the road location and profile. This could be used to change the way the road builder is paid for construction as measurements can be made to determine the volume of material that had to be moved.
- Capture imagery regularly during harvesting to improve situational awareness for harvest managers and equipment operators. With autonomous drones this could be done with little additional effort on the part of those already on site.
- Determine timber volumes stored in all locations for improved inventory control.
- Assessment of conformance with regulation, policies and procedures. Ultimately this should ensure that the management of both timber and non-timber management is effective.
There are benefits within virtually every aspect of forest management to acquiring data with a drone on an as needed basis. When data is required for larger areas or at a coarser resolution it may be best acquired via satellite or manned aircraft. As technology advances capturing data with drones will become cost effective for larger areas. At present, in some jurisdictions the necessity to keep the drone in visual line of sight negatively impacts the effectiveness of drones. However, with advances in collision avoidance systems we can expect that this limitation will be eliminated very soon.
Ultimately it will be the effective use of a data acquired in a variety of ways that will provide the most significant benefits to forest managers. The challenge will be determining an appropriate balance between resolution, cost and timeliness of data acquisition. Rapid advances in remote sensing technologies and the vehicles that carry these sensors will make this an ever-changing blend.