Precision: DD 6dp (~11 cm) · DDM/DMS sub-second · UTM/MGRS 1 m · ECEF 1 cm · Plus Code 10-digit (~14 m) · Geohash 10-char (~60 cm).
MGRS: GZD + 100km square + 5+5 digits. Accepts forms with or without spaces.
Altitude: h = H + N. H MSL (orthometric) via EGM96 geoid model (~1–2 m). AGL from Open-Meteo terrain API (Copernicus DEM, 90 m).
ECEF: WGS84 geocentric. Altitude round-trips — enter non-surface ECEF and all three altitude rows populate.
geo: URI: RFC 5870. Parses and displays altitude when present; ;params accepted but omitted.
Plus Code: full 10-digit global code only (e.g. 84VVJM49+F5). No short-code resolution.
Geohash: base-32, case-insensitive. Any length from 1 upward — longer = more precise.
Polar regions: UTM/MGRS valid from 80°S to 84°N only. UPS not implemented.
Zone exceptions: Norway (32V) and Svalbard (31X–37X) irregularities not handled — edge cases, rare in practice.
Live tracking: app opens in tracking mode and follows your GPS. Typing in a field or picking a preset switches to manual. Tap ◉ TRACK to resume.
iPhone: requires HTTPS or localhost — Safari blocks geolocation on file://. Drop on Tailscale/Caddy and it works.