Units in notices to mariners

[AdamLein]

So I've just finished updating some old charts. It has definitely been a good learning experience, but I'm pretty frustrated by the unit conventions.

The Notices to Mariners (from Notices to Mariners / Avis aux navigateurs) give locations in degrees, minutes, seconds, and tenths of seconds. The chart, however, is in degrees, minutes, and tenths of minutes (and only the 0.5' tic is labeled -- as 30"!!!). What gives? The process would have been about three times as fast if I didn't have to get out the calculator to decimal decimal seconds to decimal minutes, measure it out on the latitude scale, and then transfer the distance.

Is it the same on U.S. notices to mariners? Am I missing something here? Is it all a ploy to get me to abandon paper charts?