What's changed
We made the following changes:
- upgraded Bernese processing software from version 5.2 to 5.4
- added support for Glonass and Galileo signals in the processing
- started using coordinates calculated from our daily processing of CORS stations for the reference station coordinates — the coordinates are based on an average of 30 days of processing around the time of the submitted RINEX data
- started using a PPP process to determine the a priori coordinate for the user submitted RINEX file
- added support for a null antenna
- upgraded troposphere model to VMF3 with 1x1 degree gridded files for site specific coefficients.
Benefits and effects
These changes will mean that the ITRF coordinates generated by the service are more consistent and more accurate. However it may result in changes to the coordinates calculated by the service.
Typically the difference in coordinates between using the old and new processing is sub-centimetre, but with poor quality data or in areas where the deformation model is less accurate the differences may be up to a few centimetres.
Transition period
For some months after the upgrade you will be able to use the old processing strategy — PositioNZ-PP - GNSS Post-processing service.
This cannot be maintained indefinitely as it relies on up-to-date data from the University of Bern that will not be maintained in the future.
Accuracy of processing
The upgraded service can generate more accurate ITRF 2020 coordinates than the original service.
This comes from 3 factors, using:
- signals from multiple constellations means that it is using more data
- more consistent and current reference station coordinates
- more sophisticated processing algorithms.
This has been tested using datasets from a number of CORS stations across New Zealand and extracting test data of different session lengths.
The repeatability of the calculated coordinates based on session lengths is shown below — the plot shows the 95% confidence level for horizontal position (dh) and height (dv).
This demonstrates that the new processing algorithm is consistently more accurate than the old one. In particular, it is more accurate for heights and is more reliable for shorter session lengths (PositioNZ-PP requires session lengths of 1 hour or greater).
Null antenna support
An issue which has been experienced with some GNSS equipment is that the observations in RINEX data are already corrected from the antenna phase centre to the antenna reference point. This step is also done as part of the Bernese processing based on the antenna information in the RINEX headers. The result is that the correction is applied twice, resulting in incorrect coordinates (particularly the vertical coordinate).
In the new algorithm, PositioNZ-PP will allow you to replace the RINEX header antenna name with NULLANTENNA. This informs the algorithm that the correction has already been applied so that it won’t reapply it.
You select this option after you have uploaded your data as in the example screenshot below — the NULLANTENNA option is at the top of the list of antennae.)
