The module that makes the map real.
A sub-$300 waterproof field module built around the Quectel LC29H dual-band GNSS receiver. One per boat, one per person if needed. They form a sensor mesh on the water.
Hardware pipeline
RTK GPS
LC29H-DA dual-band L1+L5, 0.01m+1ppm CEP. Multi-constellation: GPS, GLONASS, Galileo, BeiDou, QZSS.
IMU
Gyro + accelerometer + magnetometer. Orientation, impact events, and dead reckoning through GPS shadow zones.
LoRa Radio
RTCM corrections from base station at put-in. Inter-node mesh for fleet relative positioning. No cellular required.
Logger
Local SD storage. Sync on return. Offline-first — the run is the data collection event.
How it works on the water
A base station at the put-in broadcasts RTCM corrections over LoRa for the run duration. Canyon GPS shadow zones are bridged by IMU dead reckoning — the same approach marine and aviation systems use when satellite lock is temporarily unavailable.
RTK Rover
On each boat. 0.01m+1ppm CEP. L1+L5 dual-band.
Base Station
At put-in. Outputs RTCM3 corrections over LoRa.
DR + RTK
Dead reckoning through canyon GPS shadow zones.
What the IMU captures beyond position
Hydraulic violence profile at a given flow level — how rough the ride actually is, quantified.
Actual vector of travel through each feature — where the current takes you vs. where you point the bow.
Flips, high-sides, strainer contact — distinct accelerometer signatures tagged to location and flow.
Relative positioning within the party — where swimmers are relative to safety boats.
At 10cm accuracy, a logged run is a genuine navigational artifact. The difference between consumer GPS and RTK is the difference between "somewhere near the left bank" and "river-left of the tongue, 40cm from the pour-over lip." That's the line. Hardware sales put it on the map.
The map builds itself.
Every run is a data collection event. At sufficient track density through the same feature at similar flows, a statistical route line emerges. Community validates. Layer goes live under ODbL.
Run Logged
RTK module records 10cm GPS + IMU through every feature, tagged to USGS flow at time of run.
Track Processed
Post-trip sync. Track snaps to NHD river geometry. IMU events flag candidate hazard features for community review.
Commons Enriched
Aggregate tracks generate statistical route lines. Community validates. Published to OpenRiverMap under ODbL.
Quectel LC29H
Dual-band L1+L5 GNSS. Multi-constellation. RTK-capable.