Compass Triangulation

## The Problem It Solves You can see something — smoke on a ridgeline, a distress flare, a downed aircraft, an animal, a suspicious vehicle — but you can't reach it, and "somewhere over that way" isn't a location anyone can act on. If you and a teammate (or you, moving between two spots) can each take a compass bearing toward the same thing, the point where those bearings cross *is* its location. This is classical resection, the same technique search-and-rescue teams, surveyors, and foresters have used for decades — Compass Triangulation just does the trigonometry, the mapping, and the reporting for you, in the field, on your phone. ## Getting Started ### 1. Set Your Magnetic Declination Your compass points to *magnetic* north; maps and GPS coordinates use *true* north. The gap between them — declination — varies by location and drifts over time, and it has to be corrected for or your bearings will be off. Enter it manually under **Settings**, or, with Pro, let the app fetch the current value automatically from your GPS position. ### 2. Understand the Two Numbers Per Bearing Every bearing you add shows both the **raw compass heading** (magnetic) and the **true-north-corrected heading** — the app does this conversion for you so you never have to do it by hand under pressure. --- ## Adding Bearings You have three ways to add a bearing, and you can mix all three in the same session: 1. **Live capture.** With GPS on, point your phone in the direction of the object and tap to record your current location and the device compass's heading in one action. 2. **Manual entry.** Type in an origin location and a heading directly — useful for entering a bearing someone radioed in to you. 3. **Import via QR or link.** If a teammate shares a bearing from their device, scan their QR code or open their link to add it to your session instantly. **Add at least two bearings from different locations, aimed at the same object, for the app to compute anything.** More bearings, and bearings taken from more different angles to each other, produce a tighter, more reliable result — two bearings that cross at a shallow angle leave more room for error than two that cross close to perpendicular. --- ## Reading the Result Once you have two or more non-parallel bearings, the app automatically shows: - **The intersection point** — the computed real-world location, as latitude/longitude, UTM, and MGRS - **Triangulation Confidence** (Good / Fair / Poor) — based on how sharply your bearings cross; the app tells you outright when your geometry is shaky, rather than just handing you a number - **Estimated Uncertainty** — a radius, shown as a dashed circle on the map, representing how much real-world error to expect around the computed point - **Nearest address**, when available The map shows every bearing as a line from its origin, your computed intersection as a marker, and the uncertainty circle around it. --- ## Sharing and Exporting - **QR code or link**, from the Share screen — this includes your declination setting, so whoever opens it gets the same real-world point regardless of what declination *their* device has set. - **JSON export/import** — your full bearing set, for backup or moving to another device. - **GPX export** *(Pro)* — for loading directly into Garmin devices, Gaia GPS, CalTopo, QGIS, or whatever mapping tool your team already uses.