A while back I was sent some data files from Seamap’s GunLink system
http://www.seamap.com/products/seismic/gunlink/
It has been a long time since I have done any marine work, so I can’t comment on the system itself except to say that it looks very nice and quite capable.
Unfortunately, the way they decided to record data for offline QC is not so clever (IMNSHO). Instead of creating their own dedicated format that would have suited the job and the equipment, they decided to use SEGD. The problem being that their data does not easily fit into the SEGD format. SEGD is a bad enough format as it is without further abuse!
There are distinct sets of data with different sample rates and number of samples. Their solution was to use different channel sets for each set of data, which does make sense, but decoding gets messy. To complicate it further they (can and do) use a sample rate that is not supported by the SEGD format. Nor do they identify the origin of each channel set, so, unless there are exactly 5 channel sets, there is no telling what the data represents – Near field signature, Far field Signature, Hydrophones or something else.
That made writing a viewer for it interesting, but nothing is impossible.
The viewer provides for spectral analysis and first break picking of each channel set. The usual Gain, clip and colour settings are easily accessible.
The selected channel set’s data can be written to a SEGY file
And you can generate a PDF file of the current display, as well as copying images for use in reports.
More details and the download link here:
https://seismatters.com/SMGLV.html