UAV photogrammetry checks 24 years of forest growth in British Columbia

The challenge

British Columbia's forests have been hit by a mountain pine beetle epidemic, a major Dothistroma needle blight outbreak and record wildfire seasons. Future timber supply now leans on younger managed stands, but the growth models were built on data from undisturbed forests.

In 1997, the team set up 30 stem-mapped plots in lodgepole pine stands, recording nearly 50,000 trees. Twenty-four years later they needed current volumes for every plot. Measuring every tree on the ground would have taken months.

The solution

In spring 2021 the team flew a DJI Mavic 2 Pro over all 30 plots, with missions planned in UgCS:

• Terrain following used elevation data to keep a constant height above the rolling ground, giving a steady GSD of 1.0 to 1.5 cm per pixel.
• Photogrammetry planning worked out flight lines, speed and shutter interval from the camera settings and overlap, with about 200 photos per 100 x 100 m plot and a 20 m buffer around each one.
• Repeatable missions: the same settings were reused at each site, changing only the survey polygon, so all 30 plots were captured the same way.

The images were processed in Agisoft Metashape Professional into orthomosaics, terrain and surface models, and a canopy height model. Individual trees were identified with colour, canopy height and a watershed segmentation algorithm.

The results

• Five hand-measured 3.99 m radius ground plots per hectare were used for checking. The drone and ground volumes correlated at 0.9173, and the drone estimates were then calibrated with a Ratio of Means adjustment.
• Healthy lodgepole pine fell from 74% in 1997 to 56% in 2021. Comandra blister rust caused 42% of deaths, but other damage agents together did more to reduce healthy tree numbers.
• Site Index rose by three metres or more in one-third of stands; the most productive stand went from 19.8 m to 25.3 m.
• The TASS III growth model matched the drone volumes only when updated Site Index and disease mortality were included: correlation rose from 0.5854 to 0.7348.

Tree-level checks such as health, stem defects and disease still needed field crews. Volume, canopy structure and mortality mapping were handled from the air.

Where this applies in India

The same mix of drone mapping and small ground plots suits:

• forest inventory and growth monitoring by forest departments and research institutes;
• plantation monitoring for timber, pulpwood and bamboo;
• afforestation and compensatory plantation audits;
• repeat surveys of many small plots spread over hilly terrain.

SPH Engineering's UgCS training courses are also available through HobiTech.

The equipment, available from HobiTech

Flight planning	UgCS - Drone Flight Planning Software: see UgCS PRO, UgCS EXPERT and UgCS ENTERPRISE
Drone	DJI Mavic 2 Pro was used in the study. Ask us for current compatible drones.
Processing	Agisoft Metashape Professional and ESRI ArcGIS with Spatial Analyst (used in the study)

Case study by SPH Engineering, published March 2026, based on Woods, McCulloch, Watts and Di Lucca (2026), The Forestry Chronicle, 102(1): 44–58. This page summarises it in our own words; the research was carried out by the BC Ministry of Forests and its co-authors, not by HobiTech. Read the original case study on SPH Engineering ↗