We live in a world where wireless signals surround us, effecting our every movement and more importantly our devices. If you are a UAV/Drone designer or user looking for the ultimate performance then this article is essential reading.
Traditional Manual Surveying involves taking 300 individual readings over the course of a day, after which the raw data has to be quality checked and approved to ensure the accuracy. With the advent of more sophisticated and affordable drones it is now easier than ever to produce a survey which captures over 1 million highly accurate individual data points (cm accuracy) in a single 15 minute flight, making this new technology an invaluable tool for the surveying and data collection industries.
Could Interference Stop such accurate data collection?
Interference when a UAV is in the air could prove to be detrimental to the success of the UAV’s mission.
The biggest forms interference being to the GNSS signals. This could leave the drone no option but to reduce the quality and the accuracy of the information it is storing. This could result in having to re-fly the mission once the data has been analysed. In the most extreme case, interference could result in a total loss of signal and the potential loss of the drone as it will lose tracking and positioning.
A significant source of interference on UAVs is often from other electronic sources on the drone. Their small size means that some the GNSS Antenna(s) are positioned in close proximity to other electrical and electronic systems.
Whether they are intentional or not, other sources of interference can emanate externally from the drone itself.
Some missions for which UAVs are employed are based next to roads, such as inspection of bridges and other related structures. In this environment there is an increased chance of interference from in-car devices such as jammers, this kind of device though illegal are cheap and can be easily obtained.
Some devices are capable of disabling a GNSS signal over a radius of hundreds of meters on the ground. When unhindered by ground based obstacles, the effects can be much further reaching. UAVs are particularly susceptible to these as they can often have a clear line of sight to the location of the device.
Overcoming interference on UAVs
In order to achieve both high accuracy and high rejection of interfering signals from third parties it is recommended a UAV designer considers using very accurate receivers and antennas which are designed to give highly reliable data:
Septentrio’s AsteRx4 receivers includes their proprietary AIM+ software. As well as mitigating the effects of interference, AIM+ includes a spectrum plot to view the RF input from the antenna in both time and frequency domains.
The Septentrio AsteRx4 digitises the antenna signal immediately after analogue filtering and automatically cleanses it of interference using multiple adaptive filtering stages.
At the installation stage, being able to view the RF spectrum is an invaluable tool for identifying the source of interference. Each interfering signal has its own individual footprint which allows UAV designers/users to identify sources of self-interference (motor or camera shutter noise for instance). For UAV installation the loss of RTK can be readily diagnosed and solved by moving the source of interference or placing it in a shielded case while the UAV is still in development.
When in the air, The Septentrio AsteRx4 AIM+ is able to mitigate interference from external sources: a set of configurable notch filters are complemented by an adaptive wideband filter capable of rejecting more complex types of interference such as that from chirp jammers, frequency-hopping signals from DME/TACAN devices as well as high-powered Inmarsat transmitters.
Innovelec also highly recommend Tallysman’s TW1829 which is designed with a pre-filter to increases the antennas immunity to interfering signals.
Specifically designed for use in UAVs, the TW1829 is designed using Tallysman’s unique Accutenna technology, providing dual band GPS L1/L2+ GLONASS G1/G2 coverage and is especially designed for precision dual frequency positioning where light weight is important.
Does Interference Affect your drone? Yes!
Working alongside industry experts, Innovelec Solutions is proud to bring a wealth of GNSS expertise to your finger tips.