Why Don’t AeroPoints Use RTK?

| July 24, 2017

We are often asked why AeroPoints™ don’t use RTK to process and correct their positioning data. Even if you haven’t asked this question yourself, you might want to know more about how the Global Navigation Satellite System (GNSS) is used to get an accurate position.

 

What is RTK?

Real time kinematic (RTK) is a precision GNSS technique used to capture centimeter-level survey-grade position data. A GNSS receiver known as the “base” is placed over a point with accurately known coordinates.

The base continuously observes signals from positioning satellite constellations and sends these over a radio, cellular, or satellite network link to a second receiver known as the “rover.”

By comparing the base observations to its own, the rover can cancel out the atmospheric, satellite orbit, and timing errors that affect GNSS accuracy to obtain a very accurate relative measurement between the two receivers in real time.

By adding this relative distance to the base station coordinates, the rover’s position can be determined to within a few centimeters.

 

How are AeroPoints different?

AeroPoints use a similar technique known as static post-processing. This is still a differential technique, but the base and rover send their raw GNSS observations to our cloud platform for processing after they have completed observations. This is similar to what is known as PPK when talking about post-processed onboard drone GNSS systems.

Propeller Aero AeroPoints PPK
How AeroPoints processing works

 

This approach has several advantages over RTK for drone mapping use cases:

No radio link is required when collecting data

With RTK systems the accuracy of your data is dependent on a constantly available radio link. This can be especially tricky in remote areas and when the RTK system is mounted on a moving drone.

AeroPoints don’t rely on any external communication networks during your flight, they simply need a WiFi connection at any convenient time after they have completed their observations to upload captured data back to the Propeller cloud platform.

Greater simplicity in the field

By moving the GNSS processing to our cloud servers, we made AeroPoints much simpler and easier to use than RTK systems. This approach minimizes the chance of things going wrong in the field affecting accuracy, and reduces power consumption to the point where AeroPoints run comfortably solely from the inbuilt solar panel.

Longer observations for fewer errors

Processing after the fact means that AeroPoints can be left onsite to record data for longer and more subsequent observations can be used in the processing algorithm. This is not possible in RTK as after each data point is collected the future observations won’t be available.

Using AeroPoints with an RTK-enabled drone

While it is possible to obtain survey accurate data using an onboard RTK or PPK GNSS unit, some sort of ground control data like that from AeroPoints is essential to validate the data and correct for optical distortion between your drone and the ground.

When using an RTK-enabled drone, we recommend still using AeroPoints to add ground truth to your model and as checkpoints to validate your processed model.

Abbreviations

GNSS: Global Navigation Satellite System, the catchall name for satellite positioning systems like GPS and GLONASS

Further reading

https://water.usgs.gov/osw/gps/

 

Interested in AeroPoints? Visit AeroPoints page for more information.

 

 

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