Moving-Base Real Time Kinematic (MB-RTK) GPS Solution for Angular Measurement

Full Description

A good quality, single frequency, GPS receiver will typically obtain positional accuracies within about 3m most of the time, given a good clear view of the sky. The majority of the error is accounted for by variations within the ionosphere, clock drift on board the satellites, and deviations of the satellites from their broadcast orbits.

However, two receivers placed in reasonably close proximity to each other will see the same level of error from each of these sources, and so in theory the errors ought to cancel each other out, and give an accurate relative position between the antennas. In practice, the standard GPS data chips are broadcast at too coarse a resolution to obtain significant improvements in relative results using the normal solution. However, the GPS data chips are broadcast on an RF frequency of considerably higher resolution; the L1 carrier frequency of 1575.42MHz. In single antenna operation, it is not possible to use this higher resolution frequency to obtain more accurate ranges, since the number of cycles between the receiver and the satellite cannot be counted. However, the difference in the number of carrier cycles received from a given satellite by 2 receivers in reasonably close proximity can be determined, and this is the basis of the moving-base real time kinematic technique. By resolving the difference equation resulting from the carrier differences at the 2 antennas from all common satellites, the relative position of 1 antenna compared to the other can be determined to within millimeters.

In a full RTK solution, one antenna (the base antenna) is fixed in position, and the moving antenna is tracked relative to it. This is the basis for applications such as surveying, where the base antenna is fixed in a known surveyed location and the moving antenna used to accurately locate new positions. The disadvantage of the full RTK solution is that gaining an initial lock can take a considerable time, since the solution has three unknowns; the distance between the antennas and 2 angles.

In the moving-base RTK solution, both antennas are fixed relative to each other, and the whole assembly is mounted onto the object of interest. Both antennas then move, and the angles between the antennas can change as the object upon which they are mounted either pitches, rolls or yaws, but the distance between them remains the same. The great advantage of the MB-RTK system over the full RTK system is that it is significantly quicker to obtain an initial lock, since the distance between the antennas is known. This results in lock-on times of seconds, as opposed to minutes for the full RTK system. As a result, the MB-RTK system is ideally suited to attitude measurement of moving bodies, including in situations where reception may be intermittently interrupted, such as when passing beneath bridges.

Application areas include automotive, rail, aviation and maritime uses. Please contact us at here at Hynav to discuss licensing, price, custom work or consultancy regarding this solution:

Tel: +44 (0)1773 537631

Email: sales@race-technology.com

Overview of Moving-Base Real Time Kinematic (MB-RTK) GPS Solution for Angular Measurement

Performance Parameters

Moving-Base Real Time Kinematic (MB-RTK) GPS Solution for Angular Measurement Application Programming Interface