Accurate site surveys are essential for a range of industries, from civil construction to mining, waste management to earthworks. Survey technology has advanced quickly in recent years, with drones taking to the skies to provide more accurate survey data faster, safer and more affordably than traditional survey methods. Two primary workflows are making drone technology more accessible for survey teams — RTK (real-time kinematic) and PPK (post-processing kinematic). While RTK has been used since the 1990s, more industries are relying on PPK workflows as their data processing solution. So why is drone PPK becoming the preferred method for survey processing?
PPK workflows have set a new standard for survey reliability. PPK processing solutions, like Propeller Aero, are also user-friendly and give survey teams the flexibility they need to fly challenging large-scale sites with ease. Moreover, PPK enables surveying with centimeter-level accuracy — a level of reliability that’s not always easy to achieve with RTK processing.
Here’s an in-depth look into the primary characteristics of these two processing systems showing how they differ.
Image source: Propeller Aero
RTK Basics
RTK refers to both onboard drone hardware and the data processing that occurs post-flight. Survey teams using RTK processing use drones that communicate with the global navigation satellite system (GNSS) to triangulate their location and correct positional data during flight.
But satellite data typically isn’t error prone — survey teams need to place another GNSS receiver, called a “base station” on solid ground at a point with known coordinates. By employing the base station, survey teams can boost the accuracy of RTK from a 1-meter range to a centimeter-level range.
How does using a base station improve measurements so dramatically? Essentially, the base records signals sent from positioning satellites and sends them directly to the drone during flight. The drone’s onboard GNSS technology takes the more accurate information from the base station to correct any errors affecting accuracy. The result is highly verifiable, real-time measurements of the distance between drone and base.
While RTK provides accurate, real-time data, the process relies on a consistent connection between the drone and the base. Unfortunately, the connection can be compromised if a disrupton in the signal connecting them occurs. The data collected during times when the drone and base station aren’t in-sync is generally unreliable and unusable. Breaks in the connection can directly compromise the accuracy of each flight. PPK processing eliminates this gap in data.
PPK Basics
PPK is a data processing workflow that, as its name suggests, processes data after the flight rather than in real-time. While the drone still collects data during flight with RTK technology, PPK workflows match data sets from both the base and the drone to timestamps on the photos collected during flight. Then, operators use verifiably accurate data from the base to correct the drone data. The end result is a dataset that’s accurate down to the centimeter level.
Because they’re able to reconcile data post-flight, survey teams using PPK processing don’t need to worry about maintaining a constant connection between the drone and the base station. On sites that are exceptionally large — or where signals may be unreliable — this level of flexibility is a huge advantage.
Ultimately, PPK provides a greater level of reliability than RTK. Not having to worry about signal strength allows teams to fly longer distances with user-friendly technology. Moreover, the post-flight drone data processing platform does the heavy lifting when it comes to aggregating flight data.
PPK Delivers Extraordinary Accuracy
When it comes down to RTK vs. PPK, data quality and truth are the most important factors when determining which is the best approach. It’s no surprise, then, that PPK comes out on top. It provides precise accuracy with minimal demands on operators to scrub or reconcile in-flight data.
Survey teams simply place the base station on the ground and conduct their flight. All data collected during the flight is sent automatically over Wi-Fi, and the processing software takes it from there. It’s fast, convenient, and accurate: everything operators need it to be.
For all the reasons discussed, PPK is being used widely in a variety of sectors. From large-scale earthworks projects to waste management and mining, accurate and precise location measurements are improving operations across industries, enhancing reliability in every site survey.
Image Copyright: Propellor Auto
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