Mapping What Matters: UAV Tree Canopy Assessment Across Four Development Sites

The Project

A property developer engaged Trilogy Consulting to undertake tree canopy extent assessments across four of their operational sites in South Australia, as part of preliminary planning for proposed redevelopment works at each location. The assessments were required to give the development planning team a spatially accurate, dimensioned picture of existing tree canopy at each site — identifying which trees were present, where their canopies extended, and what canopy area fell within or adjacent to proposed development footprints.

The four sites — across four sites in metropolitan and peri-urban South Australia — ranged from open greenfield-adjacent land to established established campuses with mature trees integrated into and around existing building envelopes. Each presented a different canopy density, scale, and relationship to proposed works, requiring site-specific survey planning while maintaining a consistent methodology and output format across the program.

Trilogy field operator controlling the UAV during an environmental site survey. Each flight is planned to achieve consistent altitude, overlap, and ground sampling distance across the full survey area — the basis for an accurate, measurable orthophoto.

GIS canopy mapping output — individual tree canopy polygons traced directly on the drone orthophoto, each labelled with canopy radius in metres. The nadir perspective captures true canopy extent overhead, not an estimated radius from ground observation.

The Four Sites

Site A — A large, predominantly open parcel with mature tree canopy concentrated along the northern and western portions of the site boundary. Canopy mapping focused on boundary vegetation extent and its proximity to proposed development areas. Individual canopy radii ranged from approximately 3.5 to 22.5 m, with the largest specimens in the north-western corner.

Site B — An established campus with buildings, driveways, and mature trees closely integrated within the developed envelope. Fine-scale resolution was required — distinguishing trees separated by driveways and building edges, including canopies extending over rooflines that could only be accurately captured from above. Canopy radii generally ranged from 4.5 to 15.5 m.

Site C — The densest canopy of the four, with large mature trees immediately adjacent to the existing building envelope and extending over the structure. Canopy mapping was particularly critical for understanding retention feasibility if the building were demolished or modified. Radii reached up to 17.5 m, with multiple overlapping canopies requiring individual polygon delineation.

Site D — The fourth site within an established inner-suburban setting. The canopy assessment provided spatial data complementing subsurface investigations undertaken at the same property — giving the development team an integrated above- and below-ground picture of site constraints. Mature boundary specimens with radii up to 20 m, and a more open central zone corresponding to the existing driveway and building cluster.

Methodology

Each site was surveyed using a DJI drone in a systematic grid pattern at consistent altitude and image overlap settings, calibrated to the site dimensions and canopy height to maintain uniform ground sampling distance. Flight planning accounted for existing structures, trees, and boundary features to ensure safe operation and complete spatial coverage. All surveys were completed within single site attendances.

Imagery was processed using photogrammetric software to generate georeferenced orthophotos for each site, corrected to GDA2020 — the current Australian standard coordinate reference system used in South Australian planning and cadastral datasets. This ensures canopy polygons can be directly overlaid on DA plans, cadastral boundaries, and other planning datasets without coordinate system discrepancies.

Individual tree canopy extents were mapped in GIS by tracing polygon boundaries around each visible canopy on the orthophoto. Each polygon was attributed with a canopy radius measurement, labelled on the figure to give the design team direct dimensional data without requiring additional calculation. Figure production followed a consistent format across all four sites — scaled to appropriate level, with north point, scale bar, legend, and project metadata — suitable for direct inclusion in DA packages, landscape plans, or arboricultural assessments.

The Outcome

The four-site program delivered spatially accurate, dimensioned canopy data for a development planning program covering sites from the southern suburbs to the inner city. Each site figure provides the development team with a precise, georeferenced picture of where each canopy extends and how large it is — not a general description, but a dimensioned spatial dataset ready to overlay on design drawings.

At one site in particular, the canopy data sits alongside Trilogy's geotechnical interpretive report and detailed environmental site investigation for the same property — providing the project team with an integrated dataset covering tree constraints above ground and soil conditions below. This multi-discipline contribution to a single development project reflects how Trilogy operates: as a connected team rather than separate sub-consultants.