This is an archive of GNSS-Acoustic data collected by researchers
at UCSD, Columbia, University of North Carolina, USGS, and UW
between 2018 and 2022 at three arrays established along the 
Alaska subduction zone.



Some quick notes about the data:

-We have included processed data products, raw data as collected
by the instruments, and intermediate products extracted from the
raw data that could be used to reproduce the processed data. If
you would like to reproduce the reported positions, we
recommend using the intermediate products since the raw data may
require proprietary scripts to generate the intermediate products.

-With the exception of some raw data files, all files are in an
ASCII text format.

-All solutions are reported in ITRF14.

-Time is reported in j2000 seconds, relative to 12:00, Jan 1, 2000.



For each site, you will find an offsets file with a time series of
array positions and a YEAR directory with logged files. Each YEAR
directory contains the following:

  POSITION directory containing
    -sol_out, detailed solution file (human-readable)
    -sol_cov, abbreviated solution file for easy machine-reading,
       contains offsets (m) and covariance matrix.

  APRIORI directory containing
    -ctd directory with sound velocity information (depth, velocity)
    -master file with apriori transponder positions & delay times
    -lever_arms file with body frame offsets between antenna and
       transducer

  DDD directory containing
    -pxp_tt file with twtts in microseconds
    -pxp_tt_j2k, same as pxp_tt with time in j2000 seconds
    -TWTT, 2-column time file logging ping interrogations/replies
    -INS_VEL, wave glider velocities in m/s
    -COV_VEL, wave glider velocity covariances in (m/s)^2
    -INS_RPH, wave glider roll/pitch/heading values in degrees
    -COV_RPH, wave glider roll/pitch/heading covariances
    -sfg1ddd0.yyo, daily rinex file for wave glider antenna
    -GPS_POS_FREED, antenna positions in ECEF XYZ (m)
    -POS_FREED_TRANS_TWTT, interpolated transducer positions

  RAW_DATA directory containing data packets logged by the wave glider
    - 2018-2021 data contain data logged in txt files in NMEA formats
    - 2022 data contain binary files with NMEA strings within a JSON format
    -All years contain rinex extracts from the raw data, which can be 
     replicated by the Convert tool of the Novatel Application Suite.
    -2022 binary files must be interpreted by proprietary Sonardyne scripts
     to extract NMEA records and travel times.