GNSS AUGMENTATION

In the last chapter we explained what GNSS positioning was. This system needs to be augmented in order to meet the RNP statements, specially when we are in an urban environment. In these situations, the context gets very complex and the system requires a real-time response. There are several techniques to achieve this augmentation:

1. 3D map-aided GNSS

There are several examples that improve positioning based on 3D maps. In cities, buildings can block GNSS signals making that geometry and positioning accuracy worsen. Whenever this happens 3D maps are used to counter the lack of signal. In a vehicle, the receiver is at a certain distance from the surface so the actual height can not be calculated. Again, 3D maps can help improve both, horizontal and vertical accuracy.

2. Dead reckoning augmentation

This second type involves estimating the vehicle’s state in terms of acceleration, velocity, elapsed time…A common solution is the inertial navigation system (INS), a combination of a navigation and an inertial measurement. It contains three gyroscopes and three accelerometers that obtain the mentioned data. Odometry is also quite used, it measures the number of wheel revolutions in order to calculate the steering angle to get heading of the vehicles.

3. Terrestrial radio navigation

We have two types of terrestrial navigation: (1) bespoke which is only designed for navigation and (2) overlaid positioning systems which also uses other systems such as Wifi, Bluetooth or cellular networks.

4. Vehicle-to-vehicle positioning

Vehicles transmit information about their current situation, their position can give support to GNSS with information over traffic and road conditions. It offers valuables information concerning area coverage, latency, data rate and security.

5. Visual sensor-based positioning

Finally, GNSS can also be aid with on-board sensors such as radars, lidars and cameras. For example, radar (radio detection and ranging) emits radio or micro waves based on a transmitter and a reflector of the signal and calculates distances to close objects.

Apart from all these existing technologies, there are other experimental ones that are currently being developed. As you probably know, 5G is going to change industries specially those where a real-time response is required so it is trivial to think that 5G will improve vehicle positioning at real-time. Another key point is map matching; this means going through maps accuracy and precision including as many details as possible. 

As we can see, we can not assure GNSS quality but there are several methods to improve it. These techniques integrate external information to improve navigation attributes such as accuracy, reliability and availability.  


What do you think about these methods? Do you have any new ideas for GNSS augmentation?Technology (Part Two) Technology (Part One)