Tidal Atlas

[steveej]

Morning all,

Being new to the Bristol Channel and knowing the tides being as they are, is it worth investing in a specific Tidal Atlas rather than just using the tidal information out of the Reeds Almanac?

Will it give me greater accuracy?

Thanks

 

[alant]

O

Morning all,

Being new to the Bristol Channel and knowing the tides being as they are, is it worth investing in a specific Tidal Atlas rather than just using the tidal information out of the Reeds Almanac?

Will it give me greater accuracy?

Thanks

The speed of those tides, make accuracy a bit academic.

 

[bitbaltic]

Morning all,

Being new to the Bristol Channel and knowing the tides being as they are, is it worth investing in a specific Tidal Atlas rather than just using the tidal information out of the Reeds Almanac?

Will it give me greater accuracy?

Thanks

It won't give you any greater time accuracy because the atlas is 'set up' from HW Dover, which itself comes from your almanac. Of course the atlases also say nothing about height. They are there to tell you the set and drift of the tide, which is not itself in the almanac, so you should be comparing atlas data to that represented in the tidal diamonds on your chart; to put it another way, the almanac is used for time and height information and the atlas or tidal diamond is used for set and drift information. They are telling you about different aspects of the tide.

If you are looking for set and drift accuracy, then without an atlas you would be getting that from your charts, and whether the atlas is better or not depends on the scale of the tidal atlas versus your intended journey and the charts you have to hand.

The arrows on a tidal atlas are only giving you the same information as the diamonds on the chart, but in a more pictorial form.

Looking at my Imray charts, I can see that the C59 passage chart covers about the same area as Admiralty tidal atlas NP258. However C59 only has ten tidal diamonds versus three or four times that number of arrows represented on NP258.

Looking at Imray 2600.7, which covers Cardiff to Avonmouth, there are still ten tidal diamonds and ten arrows in the part of NP258 which covers 2600.7.

So if you are staying local, there's no more info in the atlas than you'll have on your working chart, and the choice of data source is less important because the scope of the journey is more limited.

If you're making a long passage, then the atlas will present you with a more detailed overview than will the passage chart you will be working from, and in my experience makes it easier to route on longer passages or offshore races.

So I'd say buy an atlas if you're passage making (say Cardiff to Swansea) and use your tidal diamonds if you're going local (say Cardiff to portishead.

If you are looking to get the best possible height and time accuracy, buy a copy of Reeds (western is good enough) and make sure you know how to calculate secondary ports.
Hope this helps

 

[steveej]

Thanks for the detailed response.

In my Reeds Almanac there definitely small tidal atlas diagrams which, but I do not have a stand alone Bristol Channel tidal atlas to compare the two.

I believe the Tidal Atlas may be giving more 'zoomed in' view and therefore may be picking up back eddies and so forth but again I don't have one to compare.

Sounds like for £15 I need the NP258.

 

[bitbaltic]

Thanks for the detailed response.

In my Reeds Almanac there definitely small tidal atlas diagrams which, but I do not have a stand alone Bristol Channel tidal atlas to compare the two.

I believe the Tidal Atlas may be giving more 'zoomed in' view and therefore may be picking up back eddies and so forth but again I don't have one to compare.

Sounds like for £15 I need the NP258.

Yes you're right, there are the little tidal panels at the start of each sea area, I had forgotten about those.

They are much less detailed than either the chart diamond distribution or NP258 and it's adjacent atlases (I've just checked).

I don't know if they are generalised for the lower point data density. I would regard them as intended to give an overview and acceptable for unhurried cruising; I would not necessarily rely on them for optimising routing or for racing.

 

[Pigpen]

<snip>
Sounds like for £15 I need the NP258.

Have a look on Amazon or ebay before you spend so much!

 

[david_bagshaw]

Morning all,

Being new to the Bristol Channel and knowing the tides being as they are, is it worth investing in a specific Tidal Atlas rather than just using the tidal information out of the Reeds Almanac?

Will it give me greater accuracy?

Thanks

If doing a lot of critical depth anchoring I find belfield tide plotter very useful for quickly establishing the required minimum anchorage depth. Obviously you need some sort of tablet / laptop to run it on. Particularly good in rapidly changing areas such as Bristol channel. Served me well over the last 3 years 1500-2000 miles per year in south coast, BC and Irish tidal waters. Lots of new to me ports visited having moved from NL and baltic waters.

 

[King Penguin]

I made a tidal atlas by plotting all the tidal diamonds on the admiralty Bristol channel chart pack and I've got them on-line that you can download free of charge! Yep, you heard me right!

It's quite detailed and I use it all the time, as do my students. You can find it on the following link : http://www.penguinsailing.com/localguides.html

Enjoy

Ps, it's also based on Avonmouth HW, so no need to look up Dover tide times.....