How to GPS
GPS
GPS systems can provide ~10m accuracy out of the box. By combining samples to reduce noise and using data from other satellite systems (GNSS), we can reduce this variance to ~3-5m. DGPS (differential) introduces corrections from known reference points to reduce variance to ~1m.
RTK
RTK/PPK provides higher-resolution GPS data by pairing a moving (rover) GPS receiver with a static (base) GPS receiver. Conceptually, the base station broadcasts corrections once it has gathered a precise fix for its location by gathering enough samples from satellites. GPS L1 satellites are ~12500 miles / 20k kilometers away, so having an error estimate from a receiver at a known location allows us to improve our triangulation/trilateration down to the ~1 cm range (+ ~1ppm). Applying these corrections live is called RTK (real-time kinematics), while doing them after the flight is called PPK (post-processed).
Ntrip
Ntrip is a protocol for streaming GNSS/RTK corrections over an IP network, with a number of public/private providers.
Tools
- Ardusimple -- tools for capturing GPS data.
- Emlid -- tools for capturing GPS data.