Originally Posted by codprawn
For a start my comments were "tongue in cheek".
Secondly the OS map seems to be far more accurate than even the best charts - just look at the satellite/aerial view - the OS maps are made from those.
I have noticed many times in our area(Gower) that the OS maps are much better for close in work.
Codders, if I may be so bold....
I see them to be somewhat tongue in cheek, but as a respected contributor to the forum, others less experienced on the seamanship front MAY have taken the point seriously. They may have got an OS of the S of England and gone to sea. (Remember the guy who took his narrow boat out from Fleetwood, aiming for the Isle of Man. With a road atlas (where the Isle of Man was an insert on the next page!!!!)
On close inspection of the arial photo you CAN clearly see the rocks that extend across The Run that are not shown on the OS map. I believe OS don't work from Chart Datum (lowest Astro) but from some other Datum, hence this sort of omission?
Your comment about the charts being for ships is a fair one, but much of the survey work was carried out close in by RN boats with lead lines, so, where there has not been much shift they are still the best reference. Likewise OS maps aren't for navigators at sea. Prehaps a happy medium, but we should still encourage newbies to learn with a principal method, from which they can enhance and refine their skill.
Surely the skill of navigation is to use all points of reference, and have the good sense to interpret them to build a picture.