RT Software Release November 2011, Full list of changes

Software Releases

November 3, 2011

Full list of RT Software changes – November 2011

Here is a full list of the software changes in the November 2011 software release.

Forward and backwards processing

Processing the inertial data forwards and backwards in time reduces the drift when GPS is not available and tightens the error when GPS is available. To process backwards in time, the algorithm starts at the end of the file and uses the accelerations and angular rates to work out where you came from. When processing backwards the drift is reduced because the exit of a tunnel (from the forward time version) is the start of the tunnel in the backwards time version, so the drift is small. The two results are then combined, weighting the one with the highest accuracy, to give the best solution.
Processing forwards and backwards in time can result in improvements to roll, pitch and heading too. It is like having two inertial navigation systems in the vehicle at the same time and averaging them.
OxTS has been testing the forward and backwards algorithms for a few months now and we have managed to incorporate nearly all of the features of the forward (normal) processing algorithm. We have some data to show the improvements that the forward and backward processing brings and this can be downloaded. See the web page that describes the forwards and backwards processing results here…

 

Until now the position and velocity have been processed by the GPS receiver in the RT products and then used to update the Kalman filter. For most GPS receivers this isn’t a problem but on the RT2500 and RT2502 the GPS manufacture applies a filter to the velocity, which is hard for the Kalman filter to compensate. By using the gx GPS processing algorithms the raw pseudo-range and Doppler are used to compute position and velocity then used to update the Kalman filter. On the RT2500 and RT2502 products improves the accuracy for velocity by about 25%, with a corresponding improvement to heading and slip angle.

The gx GPS processing algorithms are configurable in RT-Config for both real-time and post-processed calculations. See the Options, GPS Control page.

The gx algorithms are robust in open sky conditions but they are very conservative, rejecting poor GPS readily. In urban conditions this can result in improved measurements but can also result in fewer GPS measurements so there can be more drift.

For the RT3000 and RT4000 products the gx algorithms currently do not significantly improve the results but they will form the basis of our ix algorithms in the future. The gx algorithms will also include differential processing in the future, so that the RT3000 and RT4000 can be post-processed to DGPS accuracy without needing external software. This is an area of intense research at OxTS at the moment and it will result in some fantastic improvements in the next RT release.
Filtered accelerations

The RT can now filter both the angular and linear accelerations. These are configured using RT-Config and the filtered values are output on the CAN bus and on the RT-ANA. The NCOM output retains its non-filtered outputs but the NCOM decoder will filter the outputs so that Ethernet based outputs can also be filtered. Enginuity and RT Post-process will write the filtered acceleration values to the CSV file, if the filter has been selected. RT-View has not been changed yet, so it will still show the unfiltered accelerations; this change is planned with a future update of RT-View, when there will be more measurements available for display.

New NCOM decoders

Customers using the OxTS NCOM decoders can benefit from the filters for angular acceleration and linear acceleration. All the filters have been added to the decoders so that applications can select either non-filtered or filtered measurements.

GrafNav 8.3 support

We have updated the GrafNav interface in RT Post-process so that it supports GrafNav version 8.3. It has always been possible to use GrafNav version 8.3 but only by exporting the raw GPS data and using the GrafNav interface. Now RT Post-process can reprocess the GPS data using GrafNav 8.3 automatically without having to learn and use the GrafNav interface. Advanced features will still require GrafNav to be used.

The supported versions of GrafNav in RT Post-process are now 7.6, 7.8, 8.1 and 8.3. Unfortunately GrafNav version 8.2 does not work correctly with external software and we Novatel have advised against using this version. Contact Novatel for further information.

MCOM output format

The latest version of RT Post-process supports outputting MCOM when processing data in the forwards direction. (Combined forward and backwards processing is only supported for NCOM.) MCOM is used by several software packages used in the marine industry and these can now benefit from post-processing, including using GrafNav to improve the accuracy of position in post-processing.

RT Post-process file clean-up

RT Post-process generates a lot of files while it is processing. These files can now be tidied up after processing, resulting in about 60% less disk space being used after post-processing.

RT Post-process manual

Finally we have written a manual for RT Post-process. This will be installed with the current release. You can download it here…

Calibration date output

We have added the calibration date to the NCOM status messages so that customers can find out, through software, when the RT was last calibrated. This feature will apply to new RT systems and old RT systems do not have their calibration date programmed into them.

Firmware expiry

Our demonstration systems and rental systems contain firmware that expires. Partly this satisfies export control and it gives OxTS an additional measure of protection against loss. Enginuity can now report if firmware has expired, making it clearer why an RT with expired firmware is not working.

Improvement to Korean character display

There have been several fixes to the way text is displayed on Korean computers. The DBC file has been changed so that the degrees symbol is displayed correctly. The Calibration window in Enginuity has also been updated.

Speed window in Enginuity

The speed window in Enginuity has been made sizeable so that speed can be displayed full screen. The font rendering is not perfect but it does allow customers to use a small tablet PC and to get a large display of speed from Enginuity.

The display of speed in m/s has also been fixed.