RTK vs PPK — Drone Mapping GNSS Methods Compared
RTK (Real-Time Kinematic) and PPK (Post-Processed Kinematic) are the two GNSS positioning methods that push drone mapping from metre-scale to centimetre-scale accuracy. Both rely on a known-position base station and a moving rover (the drone), and both correct for atmospheric and orbit errors that ordinary single-receiver GPS cannot. The difference is when the correction happens.
RTK in plain language
RTK corrects the drone's position in flight. A base station broadcasts correction signals over radio (or via a CORS network over LTE), the drone receives them, and the on-board GNSS solver outputs corrected fixes in real time. Geotagged photos are written with centimetre-accurate coordinates as the flight runs.
PPK in plain language
PPK records raw observation data from both the base station and the drone during the flight, then merges them after landing. The post-flight processor reconstructs corrected positions for every camera trigger. Geotags are not centimetre-accurate until processing finishes, typically a few minutes after landing.
Accuracy — what each method actually delivers
- Horizontal: Both routinely deliver 1-3 cm on a well-controlled site
- Vertical: Both routinely deliver 2-5 cm with good satellite geometry
- Repeatability: PPK has a slight edge in marginal conditions (heavy canopy, multipath) because the post-processor can use both forward and backward solutions
When RTK wins
- Open-air sites with reliable line-of-sight radio link to the base, or LTE coverage for CORS corrections
- Workflows where ground control points are not deployed and the pilot wants instant feedback that fixes are locked in
- Operations where the drone needs centimetre-accurate flight paths in real time (BVLOS pipeline inspection, automated mapping grids)
When PPK wins
- Remote sites with no radio link and no LTE (Coal Branch, remote pipeline runs, northern operations)
- Heavy multipath environments (open-pit mines, industrial facilities with large reflective surfaces)
- Long missions where occasional radio dropouts would otherwise force re-flights
- Highest-rigour engineering deliverables where the redundancy of both-direction processing is preferred
How UAV Imaging picks between them
For most central Alberta sites — aggregate yards, construction projects, urban survey, ag scouting — UAV Imaging defaults to RTK because the in-flight feedback eliminates re-fly risk. For remote-site work, deep open-pit mines, and any project where the deliverable will feed an engineering CAD model with tight tolerances, PPK is the default. Both methods are supported by the Matrice 300 RTK platform; the choice is a pre-flight planning decision, not a hardware swap.
Ground control — still useful, even with RTK / PPK
Surveyed ground control points (GCPs) provide an independent check on absolute accuracy. UAV Imaging deploys 2-4 GCPs on most engineering-grade RTK or PPK missions to validate the result against an independent measurement.