Visitors from the south coast need to be aware that, whist most of the region has been recently surveyed, there are parts (notably the west coast of Anglesey) which were last surveyed in the 1850's (eighteen hundred and fifty - it's not a typing error!). The issue of spurious precision is not academic in some of these waters.

For normal cruising, this causes no problems at all, but anyone relying on the third place of decimals on their GPS could be in for a nasty surprise. Any users of AIS (purported to be 'accurate' to 5 decimal places) need to ignore the last few places!

Most charts for British waters have been converted from the Ordnance Survey datum (OSGB) to WGS84 but the differences of 0'.01Lat and 0'.08 Long are well within the limits of accuracy of the chart and are probably best ignored. Only Imray Chart C52 currently remains in OSGB datum (January 2004).

Mark One eyeball is still the most appropriate close quarters pilotage tool around here