Tidal rates in World War 1

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  • #2874
    Brian D. H
    Participant

    I am presently investigating tidal effects during WW1. Although familiar with the use of present (modern) Admiralty Tidal Stream Atlases with their notations of Spring and Neap rates, I note that an Admiralty tidal atlas in my possession for Heligoland Bight dated 1940 specifies the MEAN rates of tides at the specific surveyed points on the charlets, with an associated calculation of 1/7.2 of the daily tidal range (r) to obtain the average range of a tide in question.
    Is anyone able to comment on the relative accuracy of this older method against the modern? And whether the 1940s method was in fact brought forward from WW1?
    The UKHO cannot comment at this stage without a more in-depth research request. I do not know when the present methods used in the current Tidal Atlases was introduced.
    I am at present using a computer program for back calculations on daily times of HW & LW.

    #2875
    Frank Scott
    Participant

    I am not entirely sure what you are trying to achieve, but for accuracy you should not use the tidal atlas – which only gives a general guide – but the tidal diamonds on the relevant large scale chart which are much more detailed. However when they came into use I am not sure. The Admiralty Pilots for the period also contain more data on tidal streams.
    If you are specifically interested in tidal stream data for Heligoland Bight, then German Naval Charts and publications would be much better than British.

    #2876
    Brian D. H
    Participant

    Thank you for this response. As part of a personal research project I am interested in certain things that happened in WW1 which may have been subject to tidal influences, both height and range, particularly near the Jade River.
    I am attempting to bring some conditions possibly experienced then, into the modern format with which I am more familiar. Older charts (1916) have tidal positions marked (pre-diamond), unfortunately not within 20 miles, and the only German chart I possess (Nr 49 from 1965, large scale of the Jade and Elbe) has no tidal info at all.
    All the older tidal information is in mean rate. I was curious as to how that related to the modern Spring and Neap categories on present charts. The tidal height information at ports is given in HW F&C – High Water Full and Change (of the Moon) – so the tidal height can be obtained and the range extracted.1
    If the calculation of 1/72r is relevant to the mean rates given in the tidal atlas or on the chart info then the approximate rate for the time can be extracted.
    It’s the matter of asking someone who may be familiar with that method of tidal calculation. I assumed that as tides have been flowing before navigators used them the Tidal Atlas would at least give me an idea.

    Note:
    1. High Water, Full and Change of the Moon, also called the Lunitidal interval or ‘Vulgar Establishment’, is effectively the interval between High Tide and the time of the Moon’s Meridian passage at the port in question at Full and New moon. It was the way that tides were calculated before the Harmonic method used today.
    It is the interval between the Moon’s Southing and the next high water at that port. Generally expressed as, e.g.: Gravesend, Ih 30m (one hour 30 minutes); Milford Haven Vh 15m (Five hours 15 minutes) etc.
    The complete calculation involves finding the Moon’s Southing on the particular day (a function of its age and epact), adding the HW F&C constant and working out local time. This can have similar accuracy to modern methods. The charts I have c.1916 are marked with the HW F&C constants for a number of ports around the North Sea. Apart from a computer programme or a list of tide tables for the period, this is a reasonably well-tried method of computing HW times and was certainly used in the 18th C. (Greenville Collins Pilot 1753) and the early 20thC. (UKHO charts refer).

    #2877
    P. H
    Participant

    The British method of calculating tidal streams for the years 1914-18 changed most markedly for Heligoland during that period. The original data is that of C N J Börgen who collected data, mostly elevational, during the 1880s. He applied harmonic methods of analysis and prediction independent of Thomson/Darwin/Roberts.
    Heinrich Rauschelbach succeeded him in his work in Germany on tides across the world in the early twentieth century. However the data collected by Börgen was also available in Britain to Edward Roberts, Harold Warburg and eventually Arthur Doodson. The German authorities also supplied them with modern prediction data up to the end of 1916.
    Warburg was particularly interested in tidal streams and after winning the Thomas Gray Memorial Prize with Doodson, they went on to produce A. T. Doodson and H. D. Warburg, The Admiralty Tide Tables Part III containing Instructions for Predicting Tides and Tidal Streams and for Analysing Observations and Tables to assist Prediction and Analysis, (London, 1938). This is more appropriate than their 1941 manual.
    Despite that Admiralty title, Doodson and Warburg undertook most of their work, particularly for the 1939-45 period, under the Liverpool Tidal Institute. The Proudman Oceanographic Laboratory now carries on their work, and the tide predicting machine made for Roberts, which Doodson and Warburg used for that most critical period, is also held in Liverpool.

    #2878
    Brian D. H
    Participant

    Thank you for the response on tidal rates, it is most helpful, as well as the note on Tide Tables pt III. Unfortunately I have been unable to source a copy as yet.
    I believe Harmonic predications are the current method used for tidal heights. As I mentioned [in my earlier signal], the 1940 Tidal Atlas deals with mean rate streams, and I have as yet been unable to find any information on how this information was used in navigational calculations, if indeed it differed very much from the current methods using Neaps and Springs.
    Is it likely that the mean rate streams were in use during WW1?
    I note that charts of the period (1916) do have information for the calculation of heights by the HW F&C method, just as they do not have Tidal Diamonds as such – just nominated locations, sometimes the crossing of Latitude And Longitude lines.
    I must point out of course that this is a theoretical exercise and that I will not be sailing with this calculated information! I suppose I need to talk to a WW2 Navigator?

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