What is PPK (Post-Processed Kinematic) & How Does it Work?

Definition

PPK stands for Post-Processed Kinematic, a high-precision positioning technique used in drone mapping and surveying. PPK corrects GPS data after a flight using post-processing software rather than relying on real-time corrections. This method improves the accuracy of drone-captured geospatial data, reducing positional errors to centimeter-level precision. PPK is commonly used in professional drone surveying, aerial mapping, and georeferencing applications.

Usage

PPK is used in drone operations that require high-accuracy geolocation without the need for a constant real-time correction link. Unlike Real-Time Kinematic (RTK), which relies on a ground-based correction signal during the flight, PPK drones store raw GPS data onboard and apply corrections after the mission using reference data from a nearby base station. This method ensures precise location tracking while reducing potential signal loss issues.

Relevance to the Industry

PPK is essential for industries where high-precision mapping and surveying are required, including construction, mining, agriculture, and environmental monitoring. It provides more reliable and accurate geospatial data than standard GPS, making it ideal for creating orthomosaic maps, digital elevation models (DEMs), and 3D reconstructions. PPK is particularly useful in areas where real-time correction signals are weak or unavailable, such as remote locations or challenging environments.

How Does Post-Processed Kinematic (PPK) Work?

Capturing and Storing GPS Data:

1. Drone Flight with Raw GNSS Data Collection:

   • GPS Data Recording: When a drone equipped with a PPK-enabled GNSS (Global Navigation Satellite System) receiver flies a mapping mission, it continuously records raw satellite positioning data. Unlike standard GPS, which typically has accuracy within a few meters, PPK captures highly precise satellite signal data without real-time corrections.
   • No Dependency on Live Correction Signals: Unlike Real-Time Kinematic (RTK), which requires a constant connection to a correction network or base station, PPK does not need a live correction link during the flight. This makes it highly reliable in remote or signal-obstructed environments, such as construction sites, forests, or mountainous regions.

2. Base Station Data Collection:

   • Reference Station Setup: A ground-based GNSS base station is placed at a known, precisely surveyed location. The base station also records raw GPS satellite data throughout the drone flight.
   • Data Synchronization: The drone and the base station collect satellite data simultaneously, but corrections are not applied in real-time. Instead, this data is stored for processing after the flight.

Post-Processing and Error Correction:

3. Data Download and Software Processing:

   • Retrieving Flight Data: After the drone completes its mission, the raw GNSS data from both the drone and the base station are downloaded to a PPK processing software for correction.
   • Applying Corrections: The software compares the drone’s recorded GPS data to the base station’s reference data. By analyzing signal discrepancies caused by atmospheric conditions, satellite clock errors, and multipath effects, the software calculates and applies precise corrections.

4. Generating Highly Accurate Geotags:

   • Georeferencing with Centimeter Accuracy: The corrected positional data is then used to accurately geotag the drone images with centimeter-level precision. This ensures that every aerial image aligns correctly with real-world coordinates, improving the accuracy of photogrammetric models.
   • Eliminating GPS Drift and Errors: The post-processing step removes errors caused by atmospheric disturbances, satellite inconsistencies, and other GPS inaccuracies that occur in real-time positioning systems.

Integration with Photogrammetry and Mapping:

5. Creating Accurate 3D Models and Maps:

   • Processing in GIS & Photogrammetry Software: The corrected geotagged images are imported into mapping and modeling software (e.g., Pix4D, Agisoft Metashape, or DroneDeploy) to create orthomosaic maps, Digital Surface Models (DSMs), and 3D reconstructions.
   • High-Precision Output: The accuracy of the final outputs is significantly improved compared to standard GPS-based mapping, making PPK essential for projects requiring sub-centimeter precision.

6. Comparing PPK with RTK:

   • PPK (Post-Processed Kinematic):
     • No need for a continuous connection to a correction signal.
     • Corrections are applied after the flight.
     • Ideal for remote areas where real-time correction signals are unreliable.
   • RTK (Real-Time Kinematic):
     • Requires a continuous live connection to a base station or network.
     • Corrections are applied during the flight.
     • Can be affected by signal loss or interference but provides instant positioning.

Applications and Industry Benefits:

7. Industries That Benefit from PPK Technology:

   • Surveying & Land Mapping: PPK provides highly accurate topographic maps for land development, construction, and urban planning.
   • Mining & Construction: Ensures precise volumetric measurements for excavation and site grading.
   • Agriculture & Forestry: Allows for detailed analysis of crop health, terrain variations, and resource management.
   • Infrastructure Inspection: Captures detailed geospatial data for roads, bridges, and utilities.

8. Advantages of PPK Over Standard GPS and RTK:

   • More Reliable than RTK: No risk of data loss due to poor connectivity or signal interference.
   • Better Accuracy than GPS: Achieves sub-centimeter precision, making

Example in Use

“The survey team used a Post-Processed Kinematic (PPK) drone to capture high-accuracy geospatial data for a new highway project, ensuring precise mapping with centimeter-level accuracy.”

Frequently Asked Questions about PPK (Post-Processed Kinematic)

1. How does PPK improve GPS accuracy?

Answer:
PPK corrects GPS data after the flight by:

• Recording raw satellite positioning data during the flight.
• Comparing it with reference data from a ground-based base station.
• Applying post-processing corrections to achieve centimeter-level accuracy.

2. How is PPK different from RTK?

Answer:

• PPK (Post-Processed Kinematic): Corrections are applied after the flight, making it more reliable in areas with poor signal reception.
• RTK (Real-Time Kinematic): Corrections are applied during the flight via a live correction link, but accuracy can be affected by signal loss or interference.

3. What are the advantages of using PPK in drone surveying?

Answer:

• Higher Reliability: No need for a continuous real-time correction link, reducing risks of signal loss.
• Increased Accuracy: Provides sub-centimeter accuracy in post-processing.
• Works in Remote Locations: Can be used in areas with weak or no network connectivity.