The Klau PPK for Drone Surveying without Ground Control Points (GCPS)
The key to accuracy in any mapping or 3D modelling project is control. This can be either GCPs (ground control points) visible in the photos, or camera locations, the precise point where each photo was taken.
Enabling your mapping data acquisition with accurate camera locations will reduce or eliminate the need for GCPs, saving on ground survey crew time and cost while increasing accuracy and reliability.
Accurate UAV Mapping
Compatible with most UAVs and cameras, including DJI, the KlauPPK system enables you to fly your missions as you do now, but achieve far better results.
The KlauPPK software applies sophisticated yet simple data management and processing to geotag photos with precise PPK positions, in any coordinate system.
Some cameras can be supplied pre-calibrated while others will require our guided on-site calibration to achieve the best possible absolute results, including height.
Placing GCPs (ground targets) is time consuming, expensive and not effective for large projects which need many well distributed ground targets to produce accurate mapping results. This typically takes much more time than the aerial data acquisition. Surveying GCPs can be a slow or sometimes impossible task and smart GCPs require time again to travel the site to be recovered after the flight.
The accuracy of a project is dependent on the distance from the GCPs and can deteriorate particularly with low quality non-metric cameras in UAVs. Photogrammetry processing time is longer with GCPs as they must be selected in the photos and the software works harder to determine the camera positions.
KlauPPK overcomes these pain points by removing the need to travel the entire site, improving logistics efficiencies, saving time and money to improve project profitability.
We do recommend that you include independent check points in your mapping to prove just how accurate KlauPPK positioning is.
RTK or PPK?
Many drone geo-referencing systems use real time kinematic (RTK) solutions with various grades of GPS receiver. RTK works to provide accurate coordinates on the fly, with base station data transmitted to the UAV for real time processing. As a real time result is not required in this application, the limitations of RTK make it a less viable solution for georeferencing.
- RTK requires a stable radio link to receive base station data which is processed on the fly.
- RTK can be prone to GPS signal blockage and radio link outages with UAV flight dynamics, where signals are obstructed or lost over long distances.
- Loss of correction data and initialization results in a smaller percentage of accurate camera positions being determined.
The better alternative to RTK is post processed kinematic (PPK), where all data is logged in the UAV and processed with base station data after the flight.
- There is no data loss or initialization loss as in RTK due to radio link limitations.
- All collected data is processed with similar algorithms to RTK, run forwards and backwards through the data.
- This ensures the most robust results possible.
PPK offers greater flexibility in operations, longer range from the base, is more reliable, more accurate and easier to use.
The KlauPPK System is based on PPK camera positioning, with sophisticate technology to address errors in photo-centre timing, aircraft attitude, camera errors and coordinate systems to fully optimise your data for photogrammetry.
Absolute geolocation accuracy table of KlauPPK unit on a Phantom4Pro
Absolute geolocation accuracy table of DJI P4PRTK
The absolute geolocation accuracy table shows the initial positioning accuracy of the image coordinates. Some suppliers provide misleading information and do not publish the absolute accuracy of the initial image positions. If image coordinates are not computed precisely or their accuracy is degraded as a result of RTK link interruption (see the right-hand table), then a few ground control points will be required to correct for this uncertainty.
The number of GCPs required depends on the surveyed area size. For example DJI suggests to use at least 3 GCPs with their P4RTK. Using the KlauPPK system on a P4P drone, unprecedented initial image positioning accuracy is achievable (see the left-hand table) thanks to the advanced hardware and software technology. This means the initial image coordinates are computed very precisely and there is no need to correct them using GCPs and/or collect additional overlapping images. Reliable, accurate initial image coordinates will contribute toward robust, precise and repeatable survey results with minimal or no ground control points required and a minimal number of images.
Adding KlauPPK post processing software to your DJI P4RTK drone will enable you to achieve more reliable and repeatable results without spending time in the filed setting up a base-station or surveying ground control points. KlauPPK software turns your drone into a static ground surveying instrument to collect check or control points and verify the accuracy of the final results.