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

1. Preparation: Verify both base and rover hardware support raw GNSS data logging. Synchronize clocks and, for drones, ensure camera trigger events are accurately logged.
2. 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.
3. Reference data acquisition: Use your own base or download CORS data for your survey window if available and compatible.
4. Post-processing: Import base and rover data into PPK software, align epochs and events, and configure processing settings (constellations, baseline length, ambiguity resolution).
5. 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

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

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.

Further Reading

• Emlid – What is PPK?
• National Geodetic Survey – CORS Network
• RTKLIB Documentation

For a comprehensive exploration of PPK workflows, software tutorials, and hardware reviews, contact our team or schedule a live demonstration.