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The Absolute Tides app, which i use, definitely uses UKHO data but it's predictions are not identical to Admiralty Easytide nor again to NavionicsĬlick to expand.Navionics products? Navionics have a mobile app, they used to make plotters. The variation will be differences in the calculation method and parameters However, since there are to the best of my knowledge only two databases of tidal harmonics covering the whole of the UK and of those only the UKHO database is at all comprehensive, i would hazard that most of the available tidal predictions are calculated from the UKHO harmonics Nor for that matter do many other sources as the detailed predictions for the tides on a particular day can vary, sometimes significantly, across sources e.g Navionics, Easytide, published tide tables and various apps which include tidal predictions

Navionics are clearly not using UKHO predictions. Navionics has certainly included tidal height predictions since i started using it in 2011 and whilst the tidal stations correspond to the UKHO tidal stations, the predictions do not I'm mystified as to why the OP has asked the question but for what it's worth there seems to be some confusion reigning There is certainly no evidence of 'non-UKHO' TSDPs in Navionics for the area of the Thames Estuary that I can see. But 'other sources' will only be very localised and I think it is only the National Authorities that Navionics could practically approach. I understand that the UKHO 'hope' that such data is shared with them. For the past year, work has been undertaken to collect data for preparation for the New Nuclear Power Station on the Dengie Penisula, the Port of London Authority has oudles of data about the Thames and the Estuary and we can be sure the Wind Farm peeps collected data. There are sources of other tidal stream data. It was obvious that no funding could be available to answer the question. I won't bore you with the reason for the question but the answer was ' there is no data for that area'. I also had an email conversation with the UKHO about tidal stream data: I asked whether there was data for a particular location where currently there was no diamond. The UKHO passed on the query to the French but I got no reply. I queried data in a diamond in the English Channel and the UKHO responded saying the data originated from the French. But not all diamonds on an Admiralty chart are sourced by the UKHO. Other positions must have been subject to specific research many, many years ago.

So I reckon we can guess where that data was collected. For example in the Thames Estuary the position of many of the tidal diamonds coincide where Trinity House used to have Lightships. I have a small library of old charts, pilot books etc so you can get an idea of where the data goes from. Not that anything about that is relevant.īut I reckon the answer to your question about TSDPs is 'probably most from the UKHO from the time Navionics started'. I always used the term 'Tide Diamonds' but I just looked up the UKHO technical term - "Tide stream data position". Tide stream data not tide table data so we wasn't thinking about the right thing.