Improve your GNSS position thanks to multi-constellation and multi-frequencySeptember 25, 2019 12:47 pm
How to improve your GNSS position thanks to multi-constellation and multi-frequency ?
A GNSS receiver calculates its distance to the satellite thanks to the time, position and trajectory of the satellite. By trilateration, it gets its position. Three minimum satellites are therefore necessary to obtain a position. This position calculation is imprecise and has errors related to the environment and the quality of the components.
Indeed the signal slows and accelerates, depending on the density of the elements crossed, which varies according to the composition of the ionosphere and the troposphere. In addition there is also an error on the position of the satellite and the precision of the atomic clocks of the satellites. The accuracy of the positioning obtained is of the order of a hundred meters.
There are several ways to correct the accuracy obtained by a gnss receiver. The main one is to use a fourth satellite to determine the offset between the atomic clocks so the position error of the three satellites used to determine the position of the receiver. This improvement is so necessary that this fourth satellite is at the minimum required to obtain a position.
A second means is coupled on all modern receivers, it is the multi-constellation. Indeed the receivers will work with several constellations at the same time to average the positions. For example, our Sirius F9P receiver will calculate positions from GPS and GLONASS at the same time, then average both positions. Besides, multipath phenomena can be reduced using more constellations.
A third lever can be added to the two previous is the fact of observing, thanks to a receiver sized for several phases. The position error is averaged, in addition to the multi constellation, on several frequencies observed (for example L1 and L2) as our Sirius F9P receivers handle.
The use of multiple signals on different carriers helps significantly improve a receiver’s position estimation in terms of accuracy and reliability. It is the most effective way of eliminating the ionospheric error from the calculation of the position. The ionospheric error varies with frequency, so it has a different impact on different GNSS signals. By comparing the delays of two GNSS signals, L1 and L2, for example, the receiver can correct the impact of ionospheric errors.
A multi-constellation receiver can access the signals of several constellations: GPS, GLONASS, BeiDou and Galileo for example. The use of other constellations, in addition to GPS, increases the number of satellites in the field of view, which has the following advantages:
-Reduced signal acquisition time.
-Improved position and accuracy of time.
-Reduced problems caused by obstructions such as buildings and foliage.
-Improved spatial distribution of visible satellites, resulting in improved dilution of accuracy.
When a receiver uses signals from a variety of constellations, the solution is integrated with redundancy. If a signal is blocked due to the work environment, it is very likely that the receiver will simply be able to pick up a signal from another constellation, thus ensuring the continuity of the solution.
Drotek multi-constellation & multi-frequency gnss receivers
We offer a complete range of new generation gnss receivers that handle multi-constellation and multi-frequency. Unlike previous U-blox GNSS module generation, new ZED-F9P high precision GNSS module now handles multi-band GNSS L1/L2 which implies better estimation and correction of ionospheric interferences. Our module will bring you all major constellations reception (GPS, GLONASS, Galileo , BeiDou, plus QZSS reception) owing to their multi-band RF front-end architecture.