There are two ways to use Base stationA GNSS receiver sitting still on a known spot. It figures out how wrong the satellite signals are right now and shares that as corrections.Full definition CorrectionsLive info from a base station about how far off the satellite signals are, so your rover can cancel out the error.Full definition.
- RTKReal-time kinematic. A way to make GPS accurate to about an inch by getting live corrections from a nearby base station.Full definition fixes your positions live, while you work. Corrections come in over a radio or the internet (using NTRIPThe standard way RTK corrections are sent over the internet. Think of it as internet radio for correction data.Full definition).
- PPKPost-processed kinematic. Like RTK, but the corrections are applied after the job using recorded data, so no live link is needed.Full definition (post-processed KinematicMeasuring while moving. The "K" in RTK and PPK.Full definition) fixes them afterwards. The RoverThe receiver that moves around the job, like a survey pole or a drone. It uses the base's corrections to find its exact spot.Full definition and a base both record raw satellite data. Back at the office, software combines the two files and works out the exact positions.
RTK is like a live sports broadcast. PPK is like watching the recording and using instant replay to get every call right.
Illustrative diagram by FixFinder, not to scale.
| RTK | PPK | |
|---|---|---|
| Needs a live link? | Yes (radio, cell data or Wi-Fi) | No |
| When you get results | Right away, in the field | After processing |
| If the signal drops | You lose the precise position for that moment | Software runs the data forward and backward, so short gaps can often be filled in |
| Where base data comes from | A paid network, a free state network, or your own base | Your own base recording, or free NOAA CORS files |
| Best for | Staking out, checking work on the spot, fast turnaround | Remote sites, places with no cell signal, a backup plan for drone mapping |
Lots of crews do both. They fly with RTK and also keep the raw recordings. If the link dropped, they can redo it with PPK. Not every drone saves raw data, so check your model's manual.
Next: PPK with NOAA CORS · Set your base with OPUS.
Sources (checked Oct 16, 2026):NGS User Guidelines for Single Base Real Time GNSS Positioning v2.1Emlid Studio docsRTKLIB (open source, T. Takasu)NOAA NGS: CORS data accessDiagrams are FixFinder illustrations. Always follow your equipment's current manual.