The recent Wingtra white paper on Reaching 1 cm (0.4 in) Absolute Accuracy showcases that the VTOL fixed-wing WingtraOne drone reaches three times higher accuracy than what other fixed-wing drones can achieve. But how does it actually work? And what do you have to do to reach such drone survey accuracy? Read further and we will guide you through the steps.
Use a WingtraOne PPK drone with a Sony RX1RII payload
WingtraOne PPK is the only broad-coverage drone to date to have achieved subcentimeter (0.4 in) absolute drone survey accuracy results.
Be aware of the distance to a base station
The achievable absolute accuracy depends on the correction data derived from the static base station logging. The closer a base station is to the flight location, the better the correction data will be to the onboard GNSS logging of the WingtraOne.
When using a continuously measuring GNSS station, make sure it is close enough. The accuracy results will reduce gradually the further you are from the station. Rule of thumb—every 10 km (6.2 mi) adds 1 cm (0.4 in) to the RMS error.
In case the GNSS station is further away, use your own base station.
Be aware of elevation influence
A long baseline most of all effects the vertical accuracy. In the case of a height difference between base station and surveying area of more than 500 m (1640 ft), accuracy becomes significantly worse. Take that into consideration when planning your projects.
Always use a high-quality, survey-grade base station
When setting up a new base station on an unknown point, let the GNSS receiver log the GPS data for a couple of hours or, even better, overnight. Logging GPS data for longer periods will help ensure higher accuracy results.
Note that if a new base station is established on a known point, the results depend on how accurately the point was measured before.
Important! Don’t forget to check minimum base station requirements, which are:
- Possibility of continuous logging with logging interval of 15s or faster (1s is recommended for highest accuracy)
- Logging at least two frequencies L1 and L2
- Receiving Constellations GPS + GLONASS (optional for high precision)
Establish checkpoints to prove the accuracy to your customer
When measuring your checkpoints, make sure to use an RTK or PPK GPS receiver. Common brands include Trimble or Leica. Using any device other than an RTK or PPK GPS receiver will compromise the accuracy.
Remember to place the tip of your GPS receiver directly on the center of the control point marker. Make sure to calibrate your GPS receiver to be level with the ground. Follow the instructions on the system provided by the measurement device manufacturer. Use a tripod to make sure the receiver is stable and does not move during the measurement process.
Be careful with different coordinate systems
WingtraOne images can be geotagged in any Earth-centered, Earth-fixed coordinate system such as WGS84. In case a local projected coordinate system is desired as an output, the transformation can be performed either in the post-processing toolchain or externally using a conversion tool suitable for the desired coordinate system. Be aware that the final results in local coordinate systems are only as good as the provided conversion tools for the local coordinate system.
Avoid environmental obstacles
The GNSS satellite signals can be blocked by big obstacles such as tall buildings, mountains or trees. Therefore when using GNSS as a surveying method, carefully choose locations where the surrounding environment does not shelter your receiver from the satellite signals.
Access raw data of the tests
No high-coverage drone to date has ever been capable of reaching subcentimeter level drone survey accuracy, and many experts were wary of trusting new facts about the WingtraOne. Thus in order to verify them, Wingtra partnered with RDO Integrated Controls, one of the largest Topcon and the largest Wingtra distributor in the US, as well as ETH Zurich, one of the best science universities in the world (Topuniversities, 2018).