We’ve all become used to knowing roughly where we are on the planet when walking or driving, thanks to GPS. But GPS can be frustratingly imprecise at times. Is it possible to use the same satellite positioning signals that enable GPS to help put us more literally ‘on the spot’, with an accuracy of centimetres rather than metres?
Real Time Kinematics technology promises just that – but until recently has been limited to high-end surveying applications due to cost, weight and size considerations. Now, a new RTK+GNSS module is combining GNSS receiver technology and real-time kinematics in a compact, lightweight size that can bring survey-level positional accuracy to everything from drones to lawnmowers.
Real Time Kinematics Technology
Figure 1: RTK technology calculates precise positions by combining traditional GNSS positioning data from at least 4 satellites with correctional data from a Base station module.
A traditional GPS receiver works by communicating with at least four satellites, using the travel time of radio signals and orbital positions to calculate the position of the receiver. However, this is only accurate to a few metres, because of errors which accumulate from atmospheric delays as the radio signals travel through the ionosphere and troposphere, satellite clock drift, multipath, and orbital positioning errors.
Real Time Kinematics uses the principle that within a certain ground radius of about 10km to 20km, these errors are consistent. Using a real time communications link with a base station that has a known precise location, a rover can receive correctional data and use differential processing achieve accurate positioning down to the centimetre level.
From Heavy Equipment, to Delivery Drones
Since its invention in 1992, RTK has been vital to the surveying and construction industries, but the expensive, bulky receivers and base stations involved limited its use outside of these specialized markets.
As GPS and RTK technology has progressed, modules have finally become affordable, compact, light and power-efficient enough to be used in a wider range of applications, including weight-sensitive UAVs.
UAVs / Drones
Once the exclusive domain of the military, the cost of owning a drone has gone down and they are now within the reach of many businesses and hobbyists. Their full potential is still being realized but they’re already being used effectively in real estate, construction, outdoor photography, and many more areas.
For many UAV applications, GPS technology is essential. More precise positioning is extremely desirable but bulky, heavy, and power guzzling receivers have made them hard to incorporate in weight and size sensitive drones.
Now, u-blox has developed an RTK module with ultra-compact dimensions, weight savings, and low power consumption, promising to help both industrial and consumer UAVs do everything they normally do much better, and to open up new applications as well.
Unmanned surveying drones with RTK technology are able to map massive areas precisely in hours, eliminating the need for surveyors to spend days on foot. Delivery drones are able to autonomously ship packages to specific doors in densely populated urban areas. Aerial photography drones are able to move into a specific position for the perfect angle, or precisely track a pre-defined route for consistent shots across multiple takes, with minimal or no human control.
Autonomous Ground Vehicles
RTK isn’t just helping aerial vehicles fly better, but is also playing an important part in helping ground vehicles drive by themselves. RTK’s centimetre-level positioning allows for lane-level guidance of vehicles. Motorized vehicles in open air environments such as carts at golf courses or personnel transportation carts at airports can be autonomously guided on pre-defined routes through RTK navigation with high precision.
Besides transporting people, autonomous forklifts that transport goods, construction equipment that knows exactly where it needs to be, autonomous lawnmowers, and automated farm equipment that plants seeds, and harvests produce with little or no human aid, are all possible with the precise navigation of RTK.
RTK for Mass Market Applications
Figure 2: The NEO-M8P RTK modules are just 12.2×16.2.4mm.
The new RTK modules from u-blox are smaller, lighter, and more power efficient than traditional receivers, making all these applications, and many more, possible. The NEO-M8P modules are smaller than a penny and just slightly thicker. Power consumption is 5 times less than existing RTK solutions, making them ideal for power and weight sensitive UAV applications. Wide temperature support and automotive AEC-Q100 qualification makes them suitable for ground vehicles as well.
With the NEO M8P’s small size, affordable price and simplified setup including survey-in functionality for the base station, RTK is no longer just the domain of professional surveyors but can help realize the next generation of precisely guided UAVs and autonomous vehicles.