Fencekeeper

You're standing in a field with a drone, and the question is always the same: how high can I legally fly here? Fencekeeper answers it. Tap the map where you're taking off — or draw your actual flight area — and it pulls the live FAA facility-map grid, checks the terrain under the whole area, and hands you the exact numbers to type into DJI Fly's Safety settings: Max Altitude and Max Distance. It even reminds you where your return-to-home altitude has to sit. And it knows about terrain — the trap almost nobody covers. FAA ceilings are measured from the ground beneath the drone, but DJI's altitude limit is measured from where you took off. Stand on a rise and fly over a valley, and your "legal" altitude quietly isn't. Fencekeeper samples USGS elevation across the whole fence, corrects your Max Altitude, and can shade the ground itself — green where your altitude is legal, amber where it's tight, red where it isn't. Then it does the thing nothing else does. Tap Track before you switch over to DJI Fly, and Fencekeeper watches your position against the fence while you fly — because pilots walk while filming, and it's easy to drift out of the area your numbers were computed for. Wander toward the edge and your phone sounds off — and your wrist too, with Apple Watch taps that quicken as you get close. What's free, forever: — Live FAA UAS Facility Map ceilings on a dark flight-deck map — Governing ceiling for your exact fence, not just the cell you're standing in — Terrain-corrected altitude limit from USGS elevation data — The two DJI Fly Safety numbers, in feet or meters, with tap-to-copy — Return-to-home altitude guidance — Pre-flight conditions: wind and gusts, Kp for GPS health, civil twilight, rain — plus a one-tap TFR check — Saved fences: name a spot, reload it in a tap, numbers recompute fresh — Warns you when your fence overlaps a 0 ft cell where LAANC can't authorize flight Pro, one purchase, no subscription: — Live pilot tracking with INSIDE / NEAR EDGE / BREACH alerts that work while DJI Fly is on screen — Apple Watch companion: fence state at a glance, wrist taps that quicken near the edge — Legality shading: the ground colored by whether your altitude is legal there — Drawn fence shapes for your real flight area — with an honest warning where DJI's circular limit can't protect you — USGS topographic and satellite map styles, fences to 8 km What it doesn't do — and you should know before you buy: it tracks this phone, not your aircraft (DJI doesn't share drone telemetry with other apps). It doesn't show TFRs, and it doesn't file your LAANC authorization — you still need an approved provider like Aloft for that. Ceilings are feet AGL from the FAA's public facility map, fetched live, so you need a data connection at the field. Built for a friend who flies, by someone who got tired of guessing.