gnssIR_matlab_v3

Update: April 11, 2020 I have updated get_navfile.m. This removes a previous poor choice of nav archive (UNAVCO), and provides two new and better ones: CDDIS and NGS. As before, it also checks SOPAC.

This code is basd on a previous matlab library that was published in GPS Solutions (https://link.springer.com/article/10.1007/s10291-018-0744-8) and the GPS Tool Box (https://www.ngs.noaa.gov/gps-toolbox/GNSS-IR.htm) That version is also hosted on this gitHub account. Version 3 is my attempt to make code available that is better oriented towards routine analysis and more similar to the python code.

There is no RH dot correction as yet. There is a simple refraction correction that you can turn on/off in the main code.

WARNING: These codes do not calculate soil moisture.

Installing the code

You need to define three environment variables:

• EXE = where the non-matlab executables will live.

• ORBITS = where the GPS/GNSS orbits will be stored

• REFL_CODE = where the reflection code file (SNR files and results) will be stored

• Until I can figure out how to access environment variables in Matlab using bash, you also need to define the wget executable and store that as environment variable WGET

Executables

• My RINEX translators are on this gitHub acccount, bu if you are using Linux on a PC or MacOS, I will be posting static executable files as soon as I get a chance. The ones you need must be named gpsSNR.e and gnssSNR.e and stored in EXE.

• CRX2RNX, Compressed to Uncompressed RINEX, which you can find at http://terras.gsi.go.jp/ja/crx2rnx.html This must be stored in the EXE directory.

Running the Code

Change this function to set your environment variables: set_reflection_env_variables.m

The main function call is gnssIR_lomb.m It has both required and optional inputs. The function run_mulitple_days.m gives you an idea of how it could be called and used in a loop (i.e. through multiple days and years). I have also provided testcase_cryosphere.m for a site in Antarctica.

Required:

• station name (4 characters, lowercase)

• year

• day of year

• freqtype, for GPS this is 1, 2, or 5. Glonass, 101 or 102. Galileo, 201, 205, 206, 207, 208.

• snrtype is integer shorthand for the kinds of elevation angle data you want to save from the RINEX file. Here are the allowed options:

• 99 5-30 elev.

• 66 < 30 elev.

• 88 5-90 elev.

• 50 < 10 elev.

• plot2screen - boolean for whether you want to see the raw data plots. You will set this to false once you understand your site.

• gps_or_gnss - 1 is for GPS (nav orbits) and 2 is for GNSS (sp3 orbits which include all constellations).

Optional inputs (in this order):

• elevation angle minimum, degrees - default is set to 0.5
• elevation angle maximum, degrees - default is set to 6
• min Reflector Height (m) - default is set to 0.5
• max Reflector Height (m) - default is set to 6
• min Azimuth, degrees - default checks 8 quadrants - 45 degrees each
• max Azimuth, degrees
• minimum allowed Lomb Scargle Periodogram amplitude - 8

Don't ask me where version 2 went - that is a secret.

Kristine M. Larson https://kristinelarson.net