Arrived before first light. Site completely clear — no other visitors at that hour, which matters when deploying ground control targets across a scheduled monument. Overcast bright, which turned out to be ideal: soft diffuse light with no hard shadow across the enginehouse faces, exactly what the reconstruction needed.
Six AprilTag GCPs placed and measured before any flying. The enginehouse geometry is demanding — the taper of the chimney stack and the internal window reveals need good oblique coverage. Three orbital passes at 40m, 20m, and 12m, followed by a straight nadir grid. Wind was calm for passes one and two. Rising slightly by the cinematic pass — logged as a mild warning but footage remained usable.
Reconstruction quality: excellent. The rough granite ashlar holds texture beautifully under photogrammetry. The interior of the enginehouse — what remains of it — required a low pass to capture the stonework detail at the base of the stack. That pass was worth the extra battery.
The castle sits in a steep-sided gorge above the East Okement river, which creates access challenges and some interesting wind behaviour as the air funnels up the valley. Site open early; English Heritage signage noted. Courtyard interior is the key challenge here — the keep walls are irregular and cast complex shadows even in flat light.
Concentric orbits at three altitudes plus an interior courtyard pass flown slow and low. The river gorge below the site produces some unusual reconstruction results at the edges — water causes floaters in photogrammetry, as expected. The castle masonry itself reconstructed cleanly.
Wind picked up during the third pass and I noted some motion blur on the outer walls facing south. Flagged for review. The northern face was solid. Will revisit for a supplementary pass on the next zero-wind window.
The exposed summit ridge of northern Dartmoor. Weather window requirements are stricter here than for sheltered valley sites — wind at that altitude is genuinely problematic and the exposure means conditions can change faster than the forecast suggests. A 5am departure on a high-pressure anticyclone morning is the target.
Strategy: don't try to reconstruct the moorland — focus coverage on the granite tors themselves. Use the landscape as atmospheric context, not as model subject. Vegetation and grass produce poor splat quality; the rock formations will be excellent.
Quarries are the best training environment for this kind of work — strong geometry, vertical walls, multiple elevations, excellent parallax from vertical flight movements. The field ops guide recommends learning quarry methodology before attempting castle-scale sites under pressure. Foggintor is accessible, photogenic, and carries genuine industrial heritage value from the Dartmoor railway era.
A slow ascent from the quarry floor up the vertical face should produce the best data. Four orbit heights minimum. Interior floor pass at low altitude for the quarry pond and cut-face detail.