The survey is the part of the work that knows things. A precise map of where the rhododendron is — and how much — turns clearance from guesswork into something targeted, measured and complete.
When to fly
The Ards survey is flown in the leaf-off window — mid-to-late February — not the May–June flowering window most people assume. With the oak, birch, hazel and larch bare, the evergreen rhododendron is the only substantial green canopy left in the woodland, and its near-infrared and red-edge signature maps the whole population, including the suppressed juveniles a bloom survey misses.
The timing also clears the low-winter-sun problem: by late February the Donegal sun has climbed to 22–25° at noon, well above the long-shadow zone of December.
The only evergreen canopy left in February is the rhododendron itself — the established scientific method for separating it from everything else.
22–25° at noon by late February — bright overcast preferred over low direct sun.
The NIR / red-edge signature catches suppressed juveniles a pink-flower survey would never see.
The survey-to-proposal pipeline
A map-backed clearance proposal on the Coillte District Manager's desk by late March 2027 — inside their planning and budget cycle. Everything is sequenced from there.
| When | Step | Output |
|---|---|---|
| Dec 2026 – Jan 2027 | IAA registration + A1/A3 certificate | Legal to fly Ards under A3 |
| Jan – early Feb 2027 | Buy and learn the drone | Mavic 3 Multispectral operational |
| Jan – Feb 2027 | First contact with Coillte Donegal | Relationship opened |
| Mid–late Feb 2027 | Survey flights + ground-truth | Raw multispectral imagery, GPS plots |
| Late Feb – mid Mar | Processing in WebODM + QGIS | Density + terrain maps, hectare figures |
| Mid–late Mar 2027 | Coillte proposal submitted | Map-backed clearance proposal |
| May – Jun 2027 | Bloom confirmation flight (optional) | Validation layer, holly cross-check |
Figure — The Ards survey-to-proposal pipeline. Licensing is done in December so it never holds up a February flight.
From a thousand photographs to a single map
The drone flies a tight back-and-forth pattern at ~75% front and 70% side overlap. Photogrammetry reconstructs the site into an orthomosaic, a surface model, a terrain model — and the difference between them, the canopy height model, the seed of future biomass estimation.
In QGIS, the Semi-Automatic Classification Plugin learns the spectral signature of known rhododendron stands and classifies every remaining pixel by similarity. The real challenge — separating rhododendron from holly — is resolved by texture, canopy continuity, the height layer and the optional bloom flight.
Equipment & licensing
| DJI Mavic 3 Multispectral | €4,600 |
| Extra flight batteries ×2 | €300 |
| Accessories | €215 |
| IAA operator registration | €41 |
| IAA A1/A3 pilot certificate | €51 |
| Software (DJI, WebODM, QGIS) | €0 |
| Total Year 1 capability | €5,207 |
Software is free and open source throughout. Funded from the LEO Feasibility Grant.
The flywheel
For every grid cell cleared, the production log captures what came out of it — density class, terrain class, green biomass, drying moisture, dry mass, biochar yield, labour days. Cell by cell, a dataset accumulates linking a remotely-sensed description of forest to the physical output it produced.
Cell by cell, a picture builds of how a stretch of forest behaves — so every estimate that follows rests on evidence, not guesswork.
Survey as a service
Everyone faces the same first question: how much invasive growth do we have, and where?
Almost no estate, land trust or county council can answer it. A day of flying and a few days of processing produces a professional, accuracy-assessed infestation map — a survey service we offer to landowners and conservation managers across the north-west.