GNATSS

GNATSS is an open-source software for processing Global Navigation Satellite Systems - Acoustic (GNSS-A) data for seafloor horizontal positioning. The software is a redevelopment of existing FORTRAN codes and shell scripts developed by C. David Chadwell for processing data including measurements made with Wave Gliders. Existing code, which includes proprietary routines, is developed and maintained by John DeSanto.

Using the software

This software is available via PyPI, the Python Package Index

You can install the software with pip directly by running the following command:

bash pip install gnatss

Once the software is installed, you should be able to get to the GNATSS Command Line Interface (CLI) using the command gnatss. For example: gnatss --help, will get you to the main GNSS-A Processing in Python help page.

```console

Usage: gnatss [OPTIONS] COMMAND [ARGS]...

GNSS-A Processing in Python

╭─ Options ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮ │ --version Show version and exit. │ │ --install-completion Install completion for the current shell. │ │ --show-completion Show completion for the current shell, to copy it or customize the installation. │ │ --help Show this message and exit. │ ╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯ ╭─ Commands ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮ │ run Runs the full pre-processing routine for GNSS-A │ ╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

```

Pre-processing routines

Currently there's a single command available in the CLI, run, which will run the full pre-processing routine for GNSS-A. You can retrieve the helper text for this command by running gnatss run --help.

```console

Usage: gnatss run [OPTIONS] CONFIG_YAML

Runs the full pre-processing routine for GNSS-A Note: Currently only supports 3 transponders

╭─ Arguments ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮ │ * config_yaml TEXT Custom path to configuration yaml file. Currently only support local files! [default: None] [required] │ ╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯ ╭─ Options ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮ │ --extract-dist-center --no-extract-dist-center Flag to extract distance from center from run. [default: extract-dist-center] │ │ --extract-process-dataset --no-extract-process-dataset Flag to extract process results. [default: extract-process-dataset] │ │ --outlier-threshold FLOAT Threshold for allowable percentage of outliers before raising a runtime error. │ │ [default: None] │ │ --distance-limit FLOAT Distance in meters from center beyond which points will be excluded from solution. Note │ │ that this will override the value set as configuration. │ │ [default: None] │ │ --residual-limit FLOAT Maximum residual in centimeters beyond which data points will be excluded from solution. │ │ Note that this will override the value set as configuration. │ │ [default: None] │ │ --residual-range-limit FLOAT Maximum residual range (maximum - minimum) in centimeters for a given epoch, beyond │ │ which data points will be excluded from solution. Note that this will override the │ │ value set as configuration. │ │ [default: None] │ │ --qc --no-qc Flag to plot residuals from run and store in output folder. [default: qc] │ │ --from-cache --no-from-cache Flag to load the GNSS-A Level-2 Data from cache. [default: no-from-cache] │ │ --remove-outliers --no-remove-outliers Flag to execute removing outliers from the GNSS-A Level-2 Data before running the solver │ │ process. │ │ [default: no-remove-outliers] │ │ --run-all --no-run-all Flag to run the full end-to-end GNSS-A processing routine. [default: run-all] │ │ --solver --no-solver Flag to run the solver process only. Requires GNSS-A Level-2 Data. [default: no-solver] │ │ --posfilter --no-posfilter Flag to run the posfilter process only. Requires GNSS-A Level-1 Data Inputs. │ │ [default: no-posfilter] │ │ --help Show this message and exit. │ ╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯ ```

Currently the pre-processing routine have been tested to only supports 3 transponders, but this will be expanded in the future.

Configuration yaml file

The run command takes in a configuration yaml file, which is used to configure the pre-processing routine. You will need to provide a config yaml file when calling gnatss run.

Here's a sample configuration yaml file:

```yaml siteid: SITE #Site Identifier campaign: Region #Geographical region/Subduction Zone timeorigin: YYYY-MM-DD 00:00:00 #Time of survey arraycenter: lat: xx.yyyy #decimal latitude lon: xxx.yyyy #decimal longitude transponders: # list out all transponder and info, each entry is a different transponder (default: 3 transponders) - lat: xx.yyyyyyyyyy #decimal latitude lon: xx.yyyyyyyyyy #decimal longitude height: -zzzz.zz #transponder depth (m, positive up) internaldelay: t.tttt #Transponder Turn-Around Time (s) svmean: vvvv.vvv #Estimate of mean sound velocity (m/s) - lat: xx.yyyyyyyyyy #decimal latitude lon: xx.yyyyyyyyyy #decimal longitude height: -zzzz.zz #transponder depth (m, positive up) internaldelay: t.tttt #Transponder Turn-Around Time (s) svmean: vvvv.vvv #Estimate of mean sound velocity (m/s) - lat: xx.yyyyyyyyyy #decimal latitude lon: xx.yyyyyyyyyy #decimal longitude height: -zzzz.zz #transponder depth (m, positive up) internaldelay: t.tttt #Transponder Turn-Around Time (s) svmean: vvvv.vvv #Estimate of mean sound velocity (m/s) traveltimesvariance: 1e-10 #Default value traveltimescorrection: 0.0 #Default value transducerdelay_time: 0.0 #Default value

Posfilter configuration

posfilter: export: full: false #false for only required fields, true to include optional RPH value and uncertainties atdoffsets: forward: 0.0053 #Value for SV3 Wave Glider rightward: 0 #Value for SV3 Wave Glider downward: 0.92813 #Value for SV3 Wave Glider inputfiles: novatel: path: /path/to/file #File with INSPVAA strings novatelstd: path: /path/to/file #File with INSSTDEVA strings gpspositions: #Assume Chadwell format, (j2000 seconds, "GPSPOS" string, ECEF XYZ coordinates (m), XYZ Standard Deviations) path: /path/to/GPSPOSFREED #File path to antenna positions, use wildcards ** for day-separated data traveltimes: #Assume Chadwell format, (Time at Ping send [DD-MON-YY HH:MM:SS.ss], TWTT1 (microseconds), TWTT2, TWTT3, TWTT4), TWTT=0 if no reply path: /path/to/pxptt

Solver configuration

solver: referenceellipsoid: #These values should be constant unless the Earth changes semimajoraxis: 6378137.000 reverseflattening: 298.257222101 gpssigmalimit: 0.05 #Uncertainty threshold for transducer positions, data with larger uncertainties ignored stddev: true #true=standard deviation, false=covariance, probably deprecated geoidundulation: xx.yy #Geoid height in m bisectiontolerance: 1e-10 #Do not change harmonicmeanstartdepth: -4.0 #Shallowest water depth for calculating mean soundvelocity from CTD data inputfiles: soundspeed: #Assume 2-column text file with depth (m), sound velocity (m/s) path: /path/to/file # deletions: # Path to deletns.dat deletions file used by Chadwell code as well # path: ../tests/data/2022/NCL1/deletns.dat #gpssolution: #Path to pre-processed input data in standard GNSS-A data format, this skips the Posfilter step # path: ../gpssolution.csv #qualitycontrol: # path: /Users/lsetiawan/Repos/SSEC/offshore-geodesy/tests/data/2022/NCL1/qualitycontrol.csv

Output configuration

output: # Directory path to output directory path: /path/to/output/ ```

Contributing

Please refer to our Contributing Guide on how to setup your environment to contribute to this project.

Thanks to our contributors so far!

Open source licensing

This has a BSD-3-Clause License, which can be found here.