Extract trackline bathymetry values using SonarWiz6 from the raw data:
1. Create a project (UTM-WGS84, Zone 19N, central meridian -69.0) and use all default import parameters for the Humminbird .DAT format in SonarWiz6 (use sensor heading, import 1024 samples per channel, use channels 1 and 2).
2. Once the .DAT file is imported, select the Tools menu in SonarWiz6, and select CSF, convert CSF file to CSV. This will save all information from the sonar file to a scratch comma-separated values (CSV) text file.
3. Using Excel (or other tabular data software), extract the date, time, altitude (depth below transducer), navigation (easting, northing of nadir line) from the CSV file created in step 2 and save these values to a new temporary scratch CSV file.
4. The DGPS horizontal coordinates recorded by the Humminbird unit are based on the WGS84 ellipsoid (WGS84 G1762, ITRF2008). Using vdatum (
https://vdatum.noaa.gov/ ), transform the horizontal UTM Zone 19 WGS84 coordinates using the file created in step 4 to the NAD83 HARN UTM Zone 19 reference frame, and save these coordinates to a new file containing date, time, transformed trackline coordinates (easting, northing), and depth below transducer (2016-030-FA_navigation.csv).
5. Using the UNIX utility gawk (Mac OS X ver 10.13.4, GNU gawk v4.2.1) to extract every 25th navigation entry from the CSV file created in step 5 (corresponding to every 1 sec) to a CSV file for efficient grid processing (2016-030-FA_navigation_dec25.csv).
Command line: gawk 'BEGIN{count=0}{if(!(count % 25))print;count++}' 2016-030-FA_navigation.csv > 2016-030-FA_navigation_dec25.csv