Many surveyors have experienced problems when they drive under bridges and the GPS receiver takes a long time to regain its high accuracy (RTK Integer) position mode. This process is not easy for GPS receivers to solve. Now the Inertial+ can help Javad GPS receivers and speed up the relock time. This new technology offers unparalleled improvements to RTK algorithms.
Using a new output format, the Inertial+ generates a serial output message in the GREIS format. This message is sent to the Javad GPS receiver. It includes time, position and accuracy information about the antenna position. The Javad GPS receiver then uses this information to speed up its ambiguity resolution algorithms and regain RTK Integer more quickly.
“Javad have focussed on improving the speed and accuracy of their RTK algorithms and they are already cited as one of the fastest in the industry,” explains Brendan Watts, “but using the input from the Inertial+ they are able to speed up the ambiguity resolution and achieve even faster relock times.”
For customers measuring the road network altitude can be very important, either for drainage or to ensure data from a laser scanner is properly geo-referenced. Typically the vertical velocity accuracy of the inertial navigation system is about 1cm/s and so the expected vertical drift after 10s is at least 10cm. Without using post-processing there is very little any inertial navigation system can do about this drift, no matter how accurate its inertial sensors are.
Using the inertial-aided RTK algorithm, the Javad receiver is able to resolve the ambiguities as fast as 4 seconds using the aiding message from the Inertial+. This significantly reduces the vertical drift of the inertial navigation system during the time that GPS position is unavailable.