jasonglee / ppp-tools

Scripts for GPS-Precise Point Positioning based on RINEX files

ppp-tools

This is a collection of python scripts for GPS-Precise Point Positioning post-processing of RINEX files. GPS-PPP solutions can be found with the following software packages:

• rtklib, http://www.rtklib.com/
• ESA gLab, 5.1.3 released 2018-01 http://gage.upc.edu/gLAB
• NRCan gpsppp (CSRS-PPP) (NOTE: this fortran code is not publicly available, but can be obtained from NRCan/CSRS for academic/non-commercial use)

In addition to the GPS-PPP software some utilities may be required:

• Teqc, for concatenating many 1-day RINEX files into multi-day files, https://www.unavco.org/software/data-processing/teqc/teqc.html, install it to e.g. /usr/local/bin, and verify with $ teqc -version that it is working. as of 2018 March the latest version is "2018Jan11"
• RNXCMP, for decompressing Hatanaka compressed RINEX files, http://terras.gsi.go.jp/ja/crx2rnx.html, install to e.g. /usr/local/bin and verify that CRX2RNX is working with $ CRX2RNX -h As of 2018 March the latest version is 4.0.7.

Running PPP

The steps for PPP-processing are roughly:

1. Download RINEX files (from e.g. BIPM or other ftp-server)
2. Optionally pre-process RINEX files (i.e. decompress Hatanaka-files, and/or assemble daily files into longer batch)
3. Download SP3 orbit and CLK clock files (from e.g. CODE or other IGS datacenter)
4. Run PPP-algorthm
5. Post-process and visualize the results

Post-Processing PPP results

Post-processing may include:

• Calculation of double-differences for time-transfer purposes, e.g. (StationA - IGS) - (StationB - IGS) = StationA - StationB.
• Some UTC-laboratories submit both a RINEX file and an "LZ" file with the offset between the RINEX receiver clock and the UTC-realization. The PPP receiver-clock result should be modified using the LZ file.
• Plotting using matplotlib
• Calculation of Allan deviations or other statistics (using e.g. allantools)
• Comparison to UTC-UTC(k) numbers published by BIPM monthly in Circular-T, or to Rapid-UTC published weekly.

Folders

The scripts store input and output files under the main folder:

• 'stations' stores RINEX and LZ files from receiver stations
• 'products' stores clock, ephemeris/orbit, and ERP files from IGS datacenters
• 'common' has common files
• 'results' stores the output results of PPP processing
• 'UTC' has Circular-T data from the BIPM ftp site.
• 'UTCr' has rapid-UTC data from the BIPM ftp site.
• 'doc' has documentation
• 'temp' is used as a temporary directory for gps-ppp calculations

ESA gLAB installation

• dowload package from http://gage.upc.edu/gLAB
• build binary gLAB_linux" with "make"
• test that it works $ ./gLAB_linux -help
• move the binary to e.g. /usr/local/bin

NRCan gpsppp Installation

This Fortran code is not publicly available, but can be obtained from NRCan/CSRS for academic/non-commercial use.

The gfortran package is required on Ubuntu. NRCAN gpsppp is compiled with

Dist34613b/source/$ gfortran -o gpsppp *.f

The resulting binary can be placed in e.g. /usr/local/bin

RTKLib installation

• clone from https://github.com/tomojitakasu/RTKLIB
• run "make" in RTKLIB/app/rnx2rtkp/gcc
• move the binary "rnx2rtkp" to e.g. /usr/local/bin
• test with rnx2rtkp -help