Work package 6 focuses on the structure, definition and implementation of GNSS processing software. This work package serves as a focal point for the integration of different work packages in iNsight and their realisation through software implementation to generate what is known as the Insight Software Suite (ISS). The work package builds on capability from the four academic institutions in the iNsight project drawing on their expertise and software libraries.

The main capability of the ISS is multi-constellation GNSS data processing. The two principle algorithms of interest are differential carrier phase processing (RTK) and Precise Point Positioning (PPP). One of the first tasks has been to build on the existing RTK GPS processing engine developed at IESSG and extend it to handle multi-constellations, principally—although not restricted to—GPS, Galileo and GLONASS. This task particularly draws on the outputs of WP2 where different timescales and reference frames must to be handled for multiple GNSS.

Another main task is to implement PPP capability in the software. PPP allows high accuracy non-differential processing of GNSS measurements by carefully handling all the error sources such as satellite clock and orbit errors (through precise products from agencies such as the IGS (http://igscb.jpl.nasa.gov/); reducing atmospheric effects through dual frequency measurements and tropospheric mapping functions; and modelling effects such as carrier phase wind-up and site displacement. Currently, the principal models have been implemented in the software including: using SP3 and high rate RINEX clock data; correcting for satellite antenna offsets; forming ionosphere free linear combinations of measurements; estimating residual tropospheric delays through mapping functions; and compensating for receiver antenna offsets.

Already, ISS is able to provide effective PPP positioning capability as the following example shows. Below are results from processing dynamic data from an aircraft using a dual frequency GPS receiver with PPP using precise orbits from IGS and high rate 5 second clock corrections from CODE (http://www.aiub.unibe.ch/content/research/gnss/code___research/index_eng.html).

The figure below compares the position accuracy from PPP by comparing to a differential RTK solution using a local base station. A comparison is given for the position error for ISS and the Waypoint GrafNav 8.30 PPP processing software. Here we see that similar position accuracies are already being achieved from both softwares. Further improvements to ISS will be made by including the remaining error models for PPP (such as site displacement effects) as well as addressing the core issues of the iNsight project of multi-constellation integration. Work package 6 will focus on optimal processing of these measurements as well as investigating issues such as INS integration and PPP research.