RTK vs PPK for Drone Mapping: What Each Does and What It Does Not Fix
RTK and PPK are two ways to give a drone's photos centimetre-level positions instead of the metre-level positions of ordinary GPS. RTK corrects the position during the flight; PPK corrects it afterwards. For mapping software the result is the same kind of input: corrected positions in the photo metadata. Neither removes the need to check the result against the ground.
What RTK and PPK are
Both rely on a reference: a base station on a known point, or a network of them. The drone's receiver measures the same satellite signals as the reference, and the difference between the two removes most of the error that ordinary GPS carries.
RTK (real-time kinematic) applies the correction during the flight, so each photo is geotagged with a corrected position as it is taken. It needs a live link to the base or network. PPK (post-processed kinematic) records the raw satellite data in flight and applies the correction afterwards with the base's recorded data, so it needs no live link but adds a processing step.
| RTK | PPK | |
|---|---|---|
| When the correction is applied | During the flight | After the flight |
| Needs a live link to a base or network | Yes | No |
| Extra processing step | No | Yes, with the base data |
| Typical risk | A dropped link during the flight | Missing or mismatched base data afterwards |
| What the photos carry | Corrected positions | Corrected positions, after processing |
What mapping software does with them
Photogrammetry software reads the corrected position from each photo's metadata and uses it as the camera position, which reduces or removes the need for ground control points. Stream Capture reads EXIF GPS, XMP tags and the RTK records that survey drones write beside their photos. It does not compute the PPK correction itself; it uses positions your PPK software or drone has already written into the photos.
What neither one fixes
Good camera positions are not the same as a correct map. A systematic offset can remain between the drone's coordinate frame and your ground survey, lens calibration can be imperfect, and weak overlap can bend a model. Height is the weak axis.
How much ground control improves a result depends on the flight, the terrain and the positioning. Independent check points tell you, and their error — not the fit at the control points — is the number to quote.
Which should you use?
Use RTK when you have a reliable link to a base or network on site and want positions as you fly. Use PPK when the link is poor or unavailable, or when you want to be able to re-process the base data later. Both can be centimetre-accurate, and for mapping either is far better than ordinary GPS.
Then check the result. Whichever you use, measure it at independent check points, and add ground control points when absolute height matters.
Frequently asked questions
What is the difference between RTK and PPK?
RTK corrects the drone's position in real time during the flight and needs a live link to a base or network. PPK records raw data and applies the correction afterwards, which needs no live link but one more processing step.
What is RTK for drones?
Real-time kinematic positioning: the drone's receiver is corrected during the flight from a base station or network, giving centimetre-level positions for each photo.
Do I need GCPs if I have RTK or PPK?
Not for strong horizontal positions, but a systematic height offset can remain, which control points remove.
Does Stream Capture do PPK processing?
No. It uses the corrected positions already written into the photos by your drone or PPK software.
Can I map with a drone that has neither?
Yes. A consumer drone's ordinary GPS is used only as a soft prior, so add ground control points when absolute position matters.
Process RTK or PPK-tagged photos and see the measured error
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