Thanks Rangiroo for the comments ;-).
In addition about french maps (paper ones):
A lot of indications are given, in term of accuracy, in the legend or in the "inserted areas" (smaller charts in the corners) that detail the density and dates of the hydrographic surveys of the charts.
Actually, some charts (or some parts
of the chart) are based on very old survey
(specially in remote
areas like polynesia) and the density of the measurment can be very poor (it is shown by the number of depth
This can lead to a "not so accurate" document and when you sail in theses areas of the chart you must stay alert and navigate with caution (although, most of the time the chart is OK for our purpose).
A good watch in the spreaders is one of the solution in tricky passage
From this year, all french paper charts shall be under WGS 84 referential, FYI.
The ones that used to be under ED50 will not be edited and sold anymore.
Another (anecdotic) info is that french charts are usually french for the french areas....and french charts covering non-french areas are usually reproducing charts form the local authorities as all the hydrographic offices are exchanging their library to cover all the world easily.
This is another point to take care: the GPS
referential : make sure you are taking in account the differences that are coming from the GPS
referential applied on the paper chart (which can not be WGS84, but something else with non US charts) while plotting a coordinate with a GPS that is usually under WGS84.
It is not recommanded, however, to change the GPS referential of your GPS - but to stay in WGS84, as this "correction" is an average and not absolute for the location you are.
It is better to "manually" add the paper chart corrections while plotting and more accurate.
Last but not least, only the ECDIS systems are officially approved and garantueed as electronic charts and, normally, without errors.
It means that all the electronics
charts under commercial
brands can have some errors (Garmin recently call back some of their products for that reason) or inaccuracy and must always be counter-check by other navigation means or procedure.
Hope this will help.