#### CFarr

##### Member

I got the information from various sources stating that the West going stream commences +0410 HW Oban.

HW Oban 28th March was 1502 (easytide) so therefore West stream starts 1912

Then I look in the tidal stream atlas with tides based on HW Dover (and Ullapool)

At 2 hrs before HW Dover the stream is shown running East.

At 1 hr before HW Dover the stream is shown running West.

Therefore I assume the change of direction happens somewhere on the cusp of the two.

HW Dover on the same date was 1828 so the HW tidal hour was 1800 to 1900 (ignoring the 2 mins).

Therefore 1 hour before is 1700 to 1800 and 2 hours before is 1600 to 1700.

The cusp of the two you would assume to be 1700 then (or somewhere 15 mins either side).

But that is over 2 hours different to the time based on HW Oban!

Assuming the Oban based times are correct due to it being the local port does that then mean that the entire Tidal Atlas based on HW Dover is then 2 hours out for that day?

I’m sure HW Oban and HW Dover are not a constant time apart and that this error will change but if you’re sailing in the area it does call the Atlas into doubt doesn’t it?

Or am I missing something here?

P.S. If you base it on the Ullapool times you get to 1800, so that's 1700, 1800 and 1912! Take your pick.