Your iPhone is now a survey instrument.
Walk the passage and the centerline builds itself: stations, splays, passage size and true bearings, ready for Survex and Therion. No tape, no book, no sketch pad on the first pass.
At a glance
| Method | Continuous centerline: walk it, the Cave Line records it |
| Stations | Dropped where you stand, named by line: A1, A2, B1 |
| Splays | Off, 6, 10 or 26 per scan station, plus any you shoot by hand |
| LRUD | From each scan, out to 10 m; out of range stays blank, never zero |
| Range | LiDAR to about 5 m; a Bluetooth laser meter beyond |
| Bearings | True north with entrance GPS and north locked; declination in Therion |
| Loop check | Misclosure and its percentage of the path |
| Export | Survex .svx, Therion .th + thconfig, PDF report, CSV, KML, GeoJSON |
| Import | Survex .svx and .3d, Therion .th: keep surveying from any station |
| iPhone | Any iPhone on iOS 26; LiDAR on Pro models from iPhone 12 Pro |
The survey crew, one phone
| Job | Traditional | SpeleoMap |
|---|---|---|
| Instruments | Distance, bearing and inclination, read and called out | The phone, continuously; true bearings once north is locked |
| Tape | Run between stations | Not needed; a laser meter for long splays if you want one |
| Book | Readings written by hand, then typed up | Saved as you go, ready for Survex and Therion |
| Sketch | Drawn at each station | Plan from the line, NSS or KSS symbols and photos on each station; final drawing in your usual tool |
| Point | Flagging at each station | A station on the map; mark only the datum, and take it with you |
Recording the survey
The traverse, recorded as you walk.
A Cave Line records your path in 3D as you move: no shots between stations, no reading instruments, no book. Long-press the map to drop a station where you stand. Stations are named by line, A1, A2, A3, and branches get their own letters.
Working beside a traditional team? Match their station numbers and the two surveys line up.
Passage shape from every station.
Every LiDAR scan measures left, right, up and down at its start and end stations, out to 10 m, plus up to 26 splays. A wall out of range stays blank, never zero, so nothing invented reaches your plot.
Past LiDAR range, pair a Bluetooth laser meter: the meter gives the distance and the phone gives the direction.
Notes and symbols on the station.
Drop NSS or KSS map symbols, typed notes, photos, video and rangefinder readings straight onto the station you stand at. Carry a Bluetooth environment sensor and every station also logs temperature, humidity and air pressure.
True bearings and drift
Tied to the real world.
At the entrance, SpeleoMap averages a GPS fix and locks true north. Bearings come out true, declination goes into Therion, and the centerline drops onto a real map in KML and GeoJSON. Skip calibration for a quick sketch, or lock GPS only for a local survey.
Honest about drift.
Any traverse drifts. Snap to a station, the entrance or a datum and SpeleoMap shows how far off you were, then re-anchors. Loops report their misclosure as a percentage of the path, the same number you would compute by hand.
Every station saves a photo, the heading and the compass reading. After a crash or a dead battery, Inherit calibration gets north back from any station.
Exports, Go and Rescue
Your formats, your tools.
Survex .svx with legs, splays and passage size. Therion .th with declination and a thconfig, ready for Loch. A PDF report with plan view, north arrow, scale bar and an LRUD station table. Each Cave Line exports as its own survey; tape lines go out as Tape Survey .svx.
Already have the cave surveyed? Import Survex .svx and .3d or Therion .th and keep surveying from any station.
Find your way, and bring a friend out.
With the entrance locked, Go routes you along the survey to any station, never through rock. If someone is hurt, Rescue records the way out and builds a 911 card with the entrance GPS, depth and distance to the patient.