Geo++ SSRZ Python Demonstrator

Disclaimer

The Geo++ SSRZ Python Demonstrator does not intend to be a tool for post-processing or real-time positioning applications. Therefore, it is not computationally optimized for such operations. Its purpose is to be a demonstrative tool that accompanies the Geo++ SSRZ format documentation.

1. Introduction

   The Geo++ SSRZ Python Demonstrator is a software package designed to decode SSRZ binary files, providing the SSRZ message content in a human-readable format and to compute the SSR components influence for a user location, dealing with general GNSS-related aspects.

   In summary, the Geo++ SSRZ Python Demonstrator can perform the following main tasks:

   • Decode SSRZ messages.
   • Compute a State Space Influence (SSI) for a user location (GNSS satellite coordinates are computed by using broadcast navigation data).

   The decoding involves the following messages:

   • Metadata (satellite, metadata, and grid groups)
   • Low and high-rate corrections
   • Global VTEC ionosphere corrections
   • Global satellite-dependent ionosphere corrections
   • Regional STEC corrections
   • Gridded ionosphere corrections
   • Regional troposphere corrections
   • Gridded troposphere corrections
   • QIX bias.

2. Requirements

   The Geo++ SSRZ Python Demonstrator has been developed and tested in Python 3.9 (64-bit) environment on Windows.

   The following elements are needed in order to use the demo:

   • a Python 3+ installation (e.g., downloading Anaconda from https://www.anaconda.com/)
   • bitstruct Python module (e.g., from cmd: "conda install bitstruct -c conda-forge")
   • crcmod Python module (e.g., from cmd: "conda install crcmod -c conda-forge")
   • tkinter Python module (e.g., from cmd: "conda install tk -c conda-forge")
   • a ssrz binary file (e.g. *.ssz).

   The python dependencies can be installed by using the following pip command in a command prompt.

   pip install -r requirements.txt
   

3. Notes

   Demo assumptions:

   • The number of regions is hard-coded to one.
   • The regional troposphere message ZM007 is always present and always the last one. Following this assumption, the .csv output is filled with the SSI influence at each epoch after the ZM007 message.

   The source code is formatted by adopting autopep8 (conformed to the PEP 8 style guide).

   The script "main.py" shows how to execute the demo. The required inputs are:

   • path of the ssrz binary file
   • name of the ssrz file
   • name of the RINEX navigation file
   • output folder (optional)
   • ellipsoidal (WGS84) latitude, longitude, and height (if no input coordinates are given default values are considered: lat = 52.5 deg, lon = 9.5 deg, height = 100 m) Other optional inputs are described in the source code. Remark: to decode, only the path and name of the ssrz file are required.

   The script "start_ssrz_demo.py" is a simple GUI to execute the demo similarly to the "main.py" script.

   The results of the decoding of the input ssrz file (binary) are saved in a text file named as the input file with "_ssr.txt" attached at the end of the name.

   The results of the ssr influence computation are saved in a text file named as the input file with either "_ssi.txt" or "_ssi.csv" attached at the end of the name. The .csv file output is activated by setting csv_out variable True when calling the demo.

   In addition to the output files, a debug file is provided for the computation of the global VTEC. This file has the same name as the input file with "_gvi.txt" attached at the end.

   A test dataset is provided within the folder "test_data".

4. Reference

   Geo++ State Space Representation Format (SSRZ) Document version 1.1.2 https://www.geopp.de/SSRZ/

5. Additional information

   Geo++ GmbH is the owner of the SSRZ Python Demonstrator. The position of one of the developers was initially funded from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No 722023.