With the increasing interest in crowdsourced bathymetry, and the number of data loggers able to store raw NMEA-0183 strings from a vessel’s GPS and depth sounder, is a need to convert raw data into easier-to-use, generic tables of latitude, longitude, date, time, speed, course, depth.

James Cook University provides an online NMEA Converter service where users can upload a zip file of input raw NMEA files and then output CSV tables, or an option to output IHO DCDB-preferred CSV tables of longitude, latitude, depth, datetime.

The backend is a python script hosted on a virtual server, protected by a DMZ firewall. The script looks for cycles of both RMC and DBT (these strings must be selected in a vessel’s chart plotter), and if present, looks for data within the fields and writes a record, then moves onto the next cycle.

The output tables can be used as is, or input to hydrographic software for 3D point cloud cleaning, tidal adjustment etc. Try it yourself with a zip file of NMEA-0183 data from the vessel Flying Fish V in the southern Great Barrier Reef.