Building precision localisation into a drone payload – what we’ve learned

It’s therefore plain to see that building precision localisation into a drone payload can be a challenging proposition. These are the challenges that OXTS has been working hard to solve over the years, and our xRED boardset GNSS/INS allows drone operators to overcome many of the accuracy challenges associated with building precision localisation into a drone payload. But even with a high-performing piece of equipment like the xRED, integration into your drone can be complex.

In this blog, we’re sharing some of the practical challenges that our team has encountered over the years developing localisation solutions for drones. If you’re involved in the building of drone positioning payloads, this blog is a must-read.

Building precision localisation into a drone – Lesson 1: Vibration dampening needs careful planning

Any GNSS/INS requires a level of vibration dampening – but when installing one on a drone, there are additional layers of complexity to account for. If you’re building precision localisation into a drone, you need to understand that drones vibrate a lot more than other vehicles! On top of that, smaller GNSS/INS units – like the xRED – are more susceptible to vibration interference than larger units, so if you’re used to working with big units, you will need more dampening than you might have expected!

An additional challenge is that different drones have different resonant frequencies. This leads to one of the major pieces of advice we would give anyone developing a drone positioning solution – make sure that your test model matches your production model as closely as possible. This is especially relevant if you’re developing a V2 model, for instance, and are considering using the V1 for testing the localisation.

Coming back to the vibration question, the only solution is to test, test, and test again. You can only tell if vibration is an issue once you’re looking at the data, which you can only do after a flight, in most cases. There is no fixed solution – you just need to build the right level of vibration dampening into your drone.

Building precision localisation into a drone – Lesson 2: airflow protection protects time sync

When testing the xRED on our drone, we discovered an interesting issue: we were getting RTK lock (the highest level of GNSS precision) far less than we were expecting to. 

After some investigation, it turned out that the GNSS sensors were the culprits. A resistor next to them that was exposed to the air was causing time drift in the system, which was preventing it from achieving RTK. We installed some shielding on the GNSS sensors, and the issue resolved.

Many GNSS/INS systems used in drones will be on printed circuit boards (PCBs) rather than fully housed units. The airflow protection that housing provides, as it turns out, has a measurable impact on the quality of the data the system produces. We now offer airflow protection on the xRED as standard as a result of this.

This is just one example of the kind of challenges that can come up during the integration process. Many will be impossible to account for, and can only be resolved by careful fault-finding and testing. Familiarity with your systems, therefore, is essential to resolving these issues quickly.

Building precision localisation into a drone – Lesson 3: boresighting is essential

When you’re trying to squeeze as much accuracy as possible out of your localisation setup, the smallest optimisations can make a huge difference. In particular, we have found that boresight calibration has the potential to change the game when it comes to LiDAR payloads.

Boresight calibration is the process of precisely aligning the coordinate frames of your GNSS/INS and your LiDAR scanner. Eliminating a misalignment of just a few tenths of a degree can dramatically increase the definition of our point clouds, remove the ‘double vision’ effect you can get in some point clouds and go some way to building precision localisation into a drone.

The importance of boresight calibration led us to speed up the development of our targetless boresight calibration solution. Previously, you needed two targets that you could survey at the start of a mission in order to perform boresight calibration – now, you can do it by surveying any flat planar surfaces at the start of your survey, and then run the calibration using the built-in tool in OXTS Georeferencer.

Much of our work developing our solutions has been done in conjunction with our clients. And the value of that partnership has been massive – for both parties. For our customers, they get access to our engineers and developers, who are working specifically on a solution for them. As a result, they get exactly the solution they need, and someone who can help them solve challenges that come up. 

In turn, OXTS gets a partner who is prepared to collaborate on integrating our technology into their product. The challenges we discover and overcome together all build up the level of expertise within our business, in ways we could never do working solely by ourselves. That expertise feeds back into our product development and customer support teams to ensure that we can continue to support all of our customers to make their projects successful. 

We hope that this blog has given you some useful practical insights into the challenges of building precision localisation into a drone. If you’ve got other challenges that you need support with, or are looking for a partner who will help you co-create a localisation solution that meets your needs, click below to talk to us today.