Terrestrial Survey Case Study
A recent study conducted by Chris Nichols from Brian Blakeman Surveys evaluated the performance of his existing Trimble GNSS equipment against Emlid Reach RS2 GNSS receivers.
Real World Survey Tasks
Equipment spec sheets don’t always tell the whole story. Therefore, the aim of this experiment was to undertake common ‘real world’ survey tasks and compare a high-end current model ‘brand-name’ receiver with an affordable alternative, evaluating the differences in performance. The survey was completed during January 2021 in central Australia, where a mix of urban and remote environments supports a range of equipment testing scenarios.
Detailed Case Study
The full case study includes:
- RTK Performance (Easy, Medium, Hard & Urban Terrain)
- RTK Performance Comparison Against Government Survey Marks Using Local Base
- RTK Performance Against Government Survey Marks Using AUSCORS
- A Comparison of RINEX Logs Post-Processed On AUSPOS
Aerial Survey Kits
Aerial Survey Case Study
At Uber Air Pty Ltd we were intrigued by the simplicity of the EMLID Reach2 Base and Rover setup in combination with our DJI Phantom 4 RTK drone. We usually use the drone as a PPK solution, using the RINEX file with Klau Geomatics’ PPK processing.
The drone mapping task over the Kulgera Roadhouse along the Stuart Highway about 280 kilometres south of Alice Springs – and no mobile phone coverage – made it like the perfect location to bring the new GPS tools to the test.
To extend our luck, the Northern Territory Government had also placed a survey benchmark nearby the roadhouse, which made this a one-day exercise without the need to post-process the location via AUSPOS.
Workflow
Onsite, the workflow was remarkably simple, with the added benefit of reduced setup time and less equipment to transport. Our standard was to use TopCon Hyper II base and receivers and a Satel Radio for the communication between the two. Even though the Satel enabled reception over a far greater distance, simplicity is key in such a rather confined location at Kulgera, hence the LoRa connection on the Emlids did not matter for the purpose of accuracy and range.
With the Emlid Reach app installed and ready to go on our iPhone, set up over the benchmark was a breeze. The rover connected instantly to the base and the ground control points were recorded.
Benchmark
We used the benchmark location also for the static PPK reference logging, with the RINEX recording over a few hours whilst setting up and flying the Phantom RTK. This gave us about 4 hours of GPS logging data that we also later put through AUSPOS to establish the global deviation of our dataset from the dated NT Government benchmark.
Retrieving the data off the Emlid is as easy as the setup. As an Apple user business, the only drag is when using an iPhone that you cannot save the downloaded file straight onto a memory device but have to go through a lengthy process of saving it on the phone then uploading the RINEX data onto a cloud-based drive before downloading and processing it on your computer. Again, this does not apply if you are using Android handhelds.
What struck us the most is how easy and fool-proof the setup of the system is. It is well designed to be operated by anyone with other qualifications than that of a surveyor, albeit without compromising on high level accuracy.
Nota bene: We did use the task to also cross-reference the PPK Klau Geomatics data processing for the Phantom RTK with another low cost solution. But this is for another field experience review.
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