Garmin 551s plotter updates

[themannsindorse]

I have a small cruiser and on board is this Garmin 551s plotter. I use the cruiser in Poole harbour Dorset UK a lot and am a bit confused about updates. My questions are:
1. Poole harbour is known for its shifting sandbanks and the plotter shows the various deep-water channels. Does my plotter update the map showing the latest surveyed channels all by itself everytime I turn the unit on and there is a new update?

2. If not then can I get a free update via the web?

3. If not then can I buy a current map showing the recently surveyed channels and download it to my PC. Assuming the answer is yes then can I use the SD card from my camera to upload the plotter?

I have downloaded a copy of the “Garmin Express application” but cannot make any sense of it.

I wold be grateful for any advice. All I want to end up with is a map that has the latest information on Poole harbour channels dredged or otherwise.
Many thanks.
Peter

[Ziggy]

Garmin GPSMAP 551s is a UK version of the US GPSMAP 541s--it comes preloaded with the UK coastal charts. It does not update the charts automatically. You will need to pay for an SD card with updated charts. Keep in mind that the Hydrographic Office charts, on which the Garmin charts are based, may not have kept up with all the changes in the channels anyway.