Tidal Diamonds

[Maso210]

Can anyone give me an indication of how far away from a tidal diamond your position needs to be before you wouldn't bother calculating the current's impact on your course to steer?

Thanks in advance!

[CharlieDelta]

Depends on the scale of the chart I suppose. Best answer would probably just be to use the nearest one, irrespective of distance, since it's all a best-guess really?

[ETwhat?]

interpolate between the two?

[CharlieDelta]

Interpolation between tidal diamonds? Not something you'll need to do for any MCA exam, and I can't imagine it being terribly accurate or even how it would work. Tidal set and rate are hugely influenced by local factors, so linear interpolation wouldn't be of much benefit.

Interpolating between springs and neaps or times for a single tidal diamond, that's doable.

[ETwhat?]

damn the answer is normally always interpolation,

[HolyNougat]

What I usually do is draw more than one in the vicinity for the same time - that will give you an idea of the general current flow for the area, it is usually not critical to know the EXACT rate for a passage (although it may be for a docking etc), but by drawing out as many as possible in the area you get a good overview of what is expected. On larger scale charts (although diamonds do not appear on very large scale of course) if you are more than about 25% of a chart away then the data is probably going to be a little dodgy... but it does depend on the nature of the topography.