Raymarine plotters serie "a", "c" and "e" are able to log tracks to a Micro-SD card. You will find the track in the file "archive.fsh". Tracks contain at least position, water depth and time. OpenSeaMap can use this format.
May be works not with older devices of "C"-Serie (capital letters).
Raymarine plotters (MFD) save recorded tracks. Fortunately these tracks do contain depth data. So if your boat is equipped with a Raymarine plotter and a sonar connected to the plotter (as usually), you are ready to start logging depths. Here is how to:
Sounding depths is done by recording the track you went, as you would do e.g. to find the way back. These tracks are exported to SD cards, afterwards.
By default tracks are recorded with few waypoints at relevant changes of course. As we want to have lots of sounded spots, we need lots of waypoints. So first you should set your plotter to record waypoints in short a tracking interval.
Go to "Chart > Menu > My Data > Track Set-Up" and set "Record Track By" to "Distance" and set "Track Interval" to an appropriate small distance.
Record track and save to SD-card
The procedure to record a track and save it to SD-Card is described very good in this document by Navionics
Offset to waterline
The depth recorded in the tracks is the one which is reported to the plotter. It is the depth below the sonar probe plus the offset, which in set in the system (e.g. depth below keel). To know the real depth below waterline, it is important to know the difference to the depth reported by the plotter. So figure out this difference and note it (manually) with the tracks recorded.
- There is an mistake in the German translation of the menu item "Save tracks to card" of the Raymarine software. What should be "Tracks speichern" is named "Einstellungen speichern". But it does export the tracks, not the settings, so just go straight forward with the menu item pictured in the document.
- While you can select one ore more tracks to be exported to the SD card or just export all tracks, it always saves a file named archive.fsh to the root of your SD card. Existing files with that name are overwritten without asking. Be careful not to loose previously exported tracks on your card. And keep this in mind when planning to track on holidays. Without renaming archives on the SD card with a PC, there is no way to save several exports to one big SD card. Prefer to take several of smaller SD cards with you and export (and delete) all tracks when the plotters memory is full.
Similar procedures should be possible with plotters of different brands. So if you have one, please have a look at yours and share the exported tracks with the developer list.