"GARPOS" (GNSS-Acoustic Ranging combined POsitioning Solver) is an analysis tool for GNSS-Acoustic seafloor positioning.

Version

Latest version is GARPOS v1.0.1 (Apr. 5. 2022)

Major change(s)

• v1.0.1: to set B-spline's knots by time interval (also need to change "Setup.ini" file)
• v1.0.1: to use Cholesky decomposition (module "sksparse" is needed)
  • NOTE: some reported that "sksparse" cannot be used on Apple M1 Chip.

Citation

for methodology

Watanabe, S., Ishikawa, T., Yokota, Y., & Nakamura, Y. (2020). GARPOS: analysis software for the GNSS-A seafloor positioning with simultaneous estimation of sound speed structure, Front. Earth Sci. (https://doi.org/10.3389/feart.2020.597532).

for code

Shun-ichi Watanabe, Tadashi Ishikawa, Yuto Nakamura & Yusuke Yokota. (2022). GARPOS: Analysis tool for GNSS-Acoustic seafloor positioning (Version 1.0.1). Zenodo. (https://doi.org/10.5281/zenodo.6414642)

Corresponding author

• Shun-ichi Watanabe
• Hydrographic and Oceanographic Department, Japan Coast Guard
• Website : https://www1.kaiho.mlit.go.jp/KOHO/chikaku/kaitei/sgs/index.html (in Japanese)

License

"GARPOS" is distributed under the [GPL 3.0] (https://www.gnu.org/licenses/gpl-3.0.html) license.

Algorithm and documentation

Please see Watanabe, S., Ishikawa, T., Yokota, Y., and Nakamura, Y., (2020) https://doi.org/10.3389/feart.2020.597532

Requirements

• Python 3.7.3
• Packages NumPy, Scipy, Pandas, Matplotlib, and Scikit-sparse are also required.
• Fortran 90 compiler (e.g., gfortran)

Environments under Anaconda for Linux is tested.

Compilation of Fortran90-based library

For the calculation of travel time, a Fortran90-based library is needed. For example, the library can be compiled via gfortran as,

gfortran -shared -fPIC -fopenmp -O3 -o lib_raytrace.so sub_raytrace.f90 lib_raytrace.f90

Path to the library should be indicated in "Settings.ini".

Usage

When using GARPOS, you should prepare the following files.

• Initial site-parameter file (e.g., *initcfg.ini)
• Acoustic observation data csv file
• Reference sound speed data csv file
• Settings file (e.g., Settings.ini)

"bin/solveSingleEpoch.py" is a driver code. Two observation epochs are stored in "sample" directory as demo data.

cd sample
./demo.sh

or run the program manually.

cd sample

# to solve position for each transponder (for epoch SAGA.1903)
solveSingleEpoch.py -i Settings-prep.ini -f initcfg/SAGA/SAGA.1903.kaiyo_k4-initcfg.ini -d demo_prep/SAGA
# to solve position for each transponder (for epoch SAGA.1905)
solveSingleEpoch.py -i Settings-prep.ini -f initcfg/SAGA/SAGA.1905.meiyo_m5-initcfg.ini -d demo_prep/SAGA

# to make the averaged array
makeFixCfg.py -d cfgfix --res_singles "demo_prep/SAGA/*res.dat"

# to solve in array-constraint condition (for epoch SAGA.1903)
solveSingleEpoch.py -i Settings-fix.ini -f cfgfix/SAGA/SAGA.1903.kaiyo_k4-fix.ini -d demo_res/SAGA
# to solve in array-constraint condition (for epoch SAGA.1905)
solveSingleEpoch.py -i Settings-fix.ini -f cfgfix/SAGA/SAGA.1905.meiyo_m5-fix.ini -d demo_res/SAGA

The following files will be created in the directory (specified with "-d" option).

• Estimated site-parameter file (*res.dat)
• Modified acoustic observation data csv file (*obs.csv)
• Model parameter list file (*m.p.dat)
• A posteriori covariance matrix file (*var.dat)

Note

Please be aware of your storage when searching hyperparameters,

since it will create result files for all combinations of hyperparameters.

List of functions

• drive_garpos (in garpos_main.py)
• parallelrun (in garpos_main.py)
  • MPestimate (in mp_estimation.py)
    • init_position (in setup_model.py)
    • make_splineknots (in setup_model.py)
    • derivative2 (in setup_model.py)
    • data_correlation (in setup_model.py)
    • calc_forward (in forward.py)
      • corr_attitude (in coordinate_trans.py)
      • calc_traveltime (in traveltime.py)
    • calc_gamma (in forward.py)
    • jacobian_pos (in forward.py)
      • corr_attitude (in coordinate_trans.py)
      • calc_traveltime (in traveltime.py)
    • outresults (in output.py)

Index list of obs.csv data

No.	Index	Description
00	SET	Names of subset in each observation (typically S01, S02,...)
01	LN	Names of survey lines in each observation (typically L01, L02,...)
02	MT	ID of mirror transponder (should be consistent with Site-parameter file)
03	TT	Observed travel time
04	ResiTT	Residuals of travel time (observed - calculated)
05	TakeOff	Takeoff angle of ray path (in degrees, Zenith direction = 180 deg.)
06	gamma	Correction term setting in the observation equations
07	flag	True: data of this acoustic shot is not used as data
08	ST	Transmission time of acoustic signal
09	ant_e0	GNSS antenna position (eastward) at ST
10	ant_n0	GNSS antenna position (northward) at ST
11	ant_u0	GNSS antenna position (upward) at ST
12	head0	Heading at ST (in degree)
13	pitch0	Pitch at ST (in degree)
14	roll0	Roll at ST (in degree)
15	RT	Reception time of acoustic signal
16	ant_e1	GNSS antenna position (eastward) at RT
17	ant_n1	GNSS antenna position (northward) at RT
18	ant_u1	GNSS antenna position (upward) at RT
19	head1	Heading at RT (in degree)
20	pitch1	Pitch at RT (in degree)
21	roll1	Roll at RT (in degree)
22	dV0	Sound speed variation (for dV0)
23	gradV1e	Sound speed variation (for east component of grad(V1))
24	gradV1n	Sound speed variation (for north component of grad(V1))
25	gradV2e	Sound speed variation (for east component of grad(V2))
26	gradV2n	Sound speed variation (for north component of grad(V2))
27	dV	Correction term transformed into sound speed variation (gamma x V0)
28	LogResidual	Actual residuals in estimation (log(TT) - log(calculated TT)

*Indices #04-#07, #22-#28 will be updated after the estimation.