"What is the main advantage of PPK over RTK?"

"PPK does not require a live data link between base and rover, allowing surveys in areas with poor or no communications. It delivers comparable or superior accuracy by applying corrections after fieldwork, and allows for reprocessing with updated reference data or algorithms."

"What equipment is needed for PPK surveying?"

"You need a GNSS receiver capable of logging raw data (RINEX format) for both the stationary base station and the mobile rover (drone, pole, vehicle, etc.), plus compatible PPK processing software and, for aerial mapping, a way to precisely log image shutter events."

"How accurate is PPK?"

"Under optimal conditions with proper setup (multi-frequency receivers, short baselines, good satellite geometry), PPK routinely achieves horizontal and vertical accuracy in the 1–3 cm range, suitable for engineering, cadastral, and scientific applications."

"Can PPK be used without setting up a local base station?"

"Yes, if there is a nearby CORS (Continuously Operating Reference Station) providing compatible data for the survey time window, its logs can be used as the base reference. Shorter baselines provide better accuracy."

"How does PPK benefit drone mapping?"

"PPK synchronizes GNSS data with camera triggers, producing highly accurate geotags for each image. This reduces or eliminates the need for ground control points (GCPs), streamlining workflows and improving mapping precision, especially in difficult-to-access areas."

"What file formats are involved in PPK?"

"Key file types include RINEX (.obs/.20o) for raw observations, navigation files (.nav/.20n), image event logs (.csv, .mrk), and output position files (.pos, .csv). All times and data must be properly synchronized."

PPK (Post-Processed Kinematic Positioning)

PPK is a GNSS-based surveying technique that achieves centimeter accuracy by post-processing raw data from both a base station and rover, eliminating the need for real-time communications.

Surveying GNSS Drone Mapping Land Surveying

PPK – Post-Processed Kinematic Positioning in Surveying

Definition

Post-Processed Kinematic (PPK) is an advanced GNSS positioning technique that delivers centimeter-level accuracy by recording raw satellite data simultaneously at a fixed base station and a moving rover (such as a drone, survey pole, or vehicle). After fieldwork, these datasets are combined and processed in specialized software to correct for GNSS errors, resulting in highly accurate positions for mapping and surveying. Unlike RTK, PPK does not require a real-time data link during data collection, allowing for robust, high-precision results even in remote or obstructed environments.

How PPK Works

PPK is based on differential GNSS positioning. Both base and rover receivers log raw observables—pseudorange and carrier phase measurements—from multiple satellite constellations (GPS, GLONASS, Galileo, BeiDou). During post-processing, the rover’s data is corrected using the base’s known position, eliminating shared errors like atmospheric delays and satellite orbit inaccuracies.

Key steps:

Raw data logging: Both receivers record all satellite signals during the survey.
Synchronization: After the survey, logs are imported into PPK software to align epochs and events (e.g., drone camera triggers).
Correction application: The software calculates corrections based on the base’s known coordinates and applies them to the rover data.
Ambiguity resolution: Carrier phase ambiguities are resolved, enabling centimeter-level precision.
Output: Corrected positions are exported for use in mapping, photogrammetry, or GIS.

PPK’s flexibility allows for repeated processing with updated reference data or improved algorithms, ensuring long-term data value.

PPK Surveying Workflow

Preparation: Verify both base and rover hardware support raw GNSS data logging. Synchronize clocks and, for drones, ensure camera trigger events are accurately logged.
Data collection: Set up the base station at a known location with a clear sky view. The rover operates as needed, logging raw GNSS data and (for aerial mapping) precise image capture times.
Reference data acquisition: Use your own base or download CORS data for your survey window if available and compatible.
Post-processing: Import base and rover data into PPK software, align epochs and events, and configure processing settings (constellations, baseline length, ambiguity resolution).
Integration: Export corrected positions for use in photogrammetry, mapping, or survey software. Validate results with ground control points or checkpoints if available.

PPK vs. RTK: Key Differences

Feature	PPK	RTK
Correction timing	After survey (post-mission)	During survey (real-time)
Communication needed	None	Continuous radio/cellular link required
Flexibility	High—no comms dependency	Limited by comms reliability
Reprocessing ability	Yes, unlimited	No—results fixed in real time
Accuracy	1–3 cm typical (with good setup)	1–3 cm typical (with good comms/fix)
Data integrity	All raw data logged for QA	May lose data if comms interrupted
Cost	Lower—no radio/cellular fees	Higher—may require modems/subscriptions
Use cases	Mapping, drone surveys, remote areas	Construction staking, machine guidance

Key Concepts and Terms

GNSS: Satellite systems providing global positioning (GPS, GLONASS, Galileo, BeiDou).
Base station: Fixed GNSS receiver at a known position, logs reference data.
Rover: Mobile GNSS receiver (drone, pole, vehicle).
RINEX: Standard format for raw GNSS data (.obs for observations, .nav for navigation).
Epoch: Timestamped set of satellite measurements.
Ambiguity resolution: Determining the integer number of carrier phase cycles for centimeter accuracy.
Baseline: Distance between base and rover (shorter is better for accuracy).
Multipath: Signal reflections causing GNSS errors.
Ground Control Points (GCPs): Surveyed points used to validate or calibrate mapping results.

Example Applications

Drone photogrammetry: PPK precisely geotags images, reducing reliance on GCPs and speeding up mapping workflows.
Topographic and boundary surveys: Enables accurate legal or engineering-grade maps even in remote or obstructed areas.
Precision agriculture: Maps field boundaries and infrastructure with high accuracy for autonomous machinery.
Construction and mining: Supports site modeling, volumetric calculations, and documentation where real-time comms may fail.
Hydrography: Georeferences echo sounder or LiDAR data on water bodies for bathymetric mapping.
Autonomous vehicle validation: Provides reference trajectories for testing and calibrating navigation systems.

PPK Data Requirements and File Types

Data Type	Description	File Extensions
Rover raw data	GNSS logs from moving platform	.obs, .bin, .rtk
Base station data	GNSS logs from reference station	.obs, .20o
Navigation files	Satellite ephemeris and clock data	.nav, .20n
Image timestamp logs	Camera shutter event records	.mrk, .csv
Correction output	Corrected rover positions (trajectory/events)	.pos, .csv, .txt

Ensure all data:

Uses compatible formats and time systems,
Covers the same time window,
Matches in satellite constellations and frequencies.

Equipment, Hardware, and Software

Receivers: Must support raw data logging (multi-frequency, multi-constellation recommended); examples include Emlid Reach RS3, DJI D-RTK 2, ArduSimple simpleRTK2B.
Drones: Survey-grade UAVs (DJI Phantom 4 RTK, Matrice 350 RTK, Mavic 3 Enterprise) with GNSS modules and hot shoe for camera event logging.
Storage: Sufficient onboard memory to prevent data loss.
Processing software: Popular options include RTKLIB (open-source), Emlid Studio, Propeller PPK, DJI Terra, and Hydromagic.
Photogrammetry suites: Agisoft Metashape, Pix4D, DJI Terra, and others accept PPK-corrected positions for high-accuracy mapping.

Summary

PPK is an essential tool for modern, high-accuracy GNSS surveying. By decoupling precise position correction from real-time communications, it empowers professionals to conduct robust mapping and data collection in any environment. Its flexibility, auditability, and ability to deliver centimeter-level results make it the preferred choice for drone mapping, land surveying, and scientific research.

Frequently Asked Questions

What is the main advantage of PPK over RTK?: PPK does not require a live data link between base and rover, allowing surveys in areas with poor or no communications. It delivers comparable or superior accuracy by applying corrections after fieldwork, and allows for reprocessing with updated reference data or algorithms.
What equipment is needed for PPK surveying?: You need a GNSS receiver capable of logging raw data (RINEX format) for both the stationary base station and the mobile rover (drone, pole, vehicle, etc.), plus compatible PPK processing software and, for aerial mapping, a way to precisely log image shutter events.
How accurate is PPK?: Under optimal conditions with proper setup (multi-frequency receivers, short baselines, good satellite geometry), PPK routinely achieves horizontal and vertical accuracy in the 1–3 cm range, suitable for engineering, cadastral, and scientific applications.
Can PPK be used without setting up a local base station?: Yes, if there is a nearby CORS (Continuously Operating Reference Station) providing compatible data for the survey time window, its logs can be used as the base reference. Shorter baselines provide better accuracy.
How does PPK benefit drone mapping?: PPK synchronizes GNSS data with camera triggers, producing highly accurate geotags for each image. This reduces or eliminates the need for ground control points (GCPs), streamlining workflows and improving mapping precision, especially in difficult-to-access areas.
What file formats are involved in PPK?: Key file types include RINEX (.obs/.20o) for raw observations, navigation files (.nav/.20n), image event logs (.csv, .mrk), and output position files (.pos, .csv). All times and data must be properly synchronized.

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