![]() How would I know that BTW? 'local knowledge' again? I cannot see 2.2M on my chart, so I guess that is knowledge people are born with (not me though). ![]() That would probably mean I am now about 1/2 meter out. OK, so the top of the slip may indeed be 2.2M high. I just want to get it *somewhat* right, that's all - to give myself some confidence in what I do in the future. It was only an exercise (for me) such that I can have some kind of faith in the data that I gather from charts and tidal predictions and how to apply that information. Like I said, I made many assumptions of which I claim no accuracy. but without local knowledge (which I don't have) I wouldn't argue with anyone who suggested any other figure between 0 and 2m !! We can see from the chart that the top of the slip is above MHWS, (because it is coloured yellow) and we can see that the bottom of the slip is above CD (because it is coloured green) Personally, I would guess at about 1m above CD. In December and June, it will generally get nowhere near it.Īt Town Quay Poole, for instance, Mean Low Water Springs is 0.6m - which means that although some Low waters will be more than 0.6m above Chart Datum, there will be roughly the same number that are less than 0.6m above CD. The logic is that they are as pessimistic as possible.īut it is a bit of an oversimplification to say that there is "always at least a metre more water than on the chart." At times (around March and September) low water will fall very close to LAT. ![]() HLB is broadly right when he says that there is always more water (and more headroom) than the chart shows, because the charted depths and drying heights are shown above Lowest Astronomical Tide, while bridge clearances are measured above Highest Astronomical Tide. The trouble is lack of information about the slip, rather than lack of information about the tide.Įven if you don't want to/can't be bothered to/don't know how to read a tide table will do it for you for free: you don't even have to register.
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