	Can I obtain tidal predictions for foreign ports?

	Yes, but there are conditions attached to this. Where the UKHO owns the underlying data upon which the tidal predictions are computed, then we are able to compute the bespoke predictions in the normal way. However, where the UKHO is not the owning authority, then you must seek permission from the relevant Foreign Government Hydrographic Office so that they may permit us to compute those predictions accordingly. Contact lists are available on the International Hydrographic Organization (IHO) website at www.iho.shom.fr. UKHO Copyright Section (copyright@ukho.gov.uk) can assist in determining which foreign ports are available directly, and those for which permission must be sought prior to release of the predictions.

	Can I obtain tidal predictions for periods of less than one calendar year?

	Not via the Tidal Prediction Service (TPS). For such information you can obtain/view the relevant volume of Admiralty Tide Tables (ATT) and obtain the predictions for Standard Ports directly from there, or compute predictions for Secondary Ports. ATT can be purchased from any Admiralty Distributor listed at www.ukho.gov.uk/howToBuy, or via our Admiralty Online shop at www.admiraltyshop.co.uk. It may also be possible to view it free of charge in a good reference library. The EasyTide website (www.ukho.gov.uk/easytide) will allow you to obtain these predictions quickly, free for the next seven days, and for a nominal charge for longer time periods. The UKHO also publishes tidal prediction software entitled TotalTide (product number DP550) and SHM for Windows (DP560) which provide tidal predictions - see www.ukho.gov.uk/total_tide.html and Electronic Products and Services for details.

	Can I obtain back-dated tidal predictions?

	Yes. Back-dated bespoke predictions can be provided via the TPS for the appropriate charges as listed; however, EasyTide (www.ukho.gov.uk/easytide) provides the facility to obtain predicted data back to the year AD100 and so should be used as the primary tool, especially if the data required covers disjointed periods of time. It is important to realise that the UKHO tidal database is subject to continuous updating, where new data is added to the database as it becomes available, and as new tidal analyses are completed. Therefore, back-dated predictions computed today may not necessarily agree with those actually published at that time.

	How far into the future can you predict for, and can I obtain predictions for ‘x’ years from now?

	Theoretically, tidal predictions can be produced for any number of years into the future. However, as with the provision of back-dated predictions, the UKHO tidal database is being continuously updated and so cannot release predictions to customers who are intending to publish the data for years over and above those already published in Admiralty Tide Tables (ATT), or which are about to be published in the next year's editions. This is so that UKHO can guarantee that predictions published in the ATT match those published in the individual tide tables for the relevant years concerned. If required a ‘standing order’ arrangement can be initiated where a quotation can be supplied year-on-year for the next year's data. Predictions which are to be used for planning purposes can be supplied in advance for years other than already published but it is still important to emphasise that there may be slight differences with these when compared with predictions eventually published in ATT. Once again, EasyTide (www.ukho.gov.uk/easytide) can be used to obtain tidal predictions for up to 50 years in advance, to be used with prudence.

	Can I obtain Tidal Stream predictions?

	Not via the TPS, which provides tidal height predictions only. All tidal stream data, where available, is contained on the largest scale Admiralty Charts of the particular area concerned. In the main it takes the form of the position marked by a Tidal Stream Diamond, which then refers to a table of Mean Spring and Mean Neap Rates and Directions for the whole tidal cycle, i.e. from 6 hours before to 6 hours after the time of High Water at a suitable reference port (Standard Port), the predictions for which can be obtained from EasyTide or the relevant volume of ATT. The UKHO publishes a series of Tidal Stream Atlases, covering the north-west European Continental Shelf, displaying structured observed tidal stream rates and directions, embellished by schematic flow diagrams, intended for navigation. Please see http://www.ukho.gov.uk/admiralty_tidal_stream_atlases.html for details. You can also obtain daily tidal stream predictions in regions where they are available in ATT Volumes 3 & 4. In addition, Volumes 2, 3 & 4 of ATT contain the necessary data (Harmonic Constants) which enable the user to obtain tidal stream predictions via the use of the Simplified Harmonic Method of Tidal Prediction (SHM) in areas where a diurnal tidal regime predominates. The SHM methodology is explained in each Volume of ATT, and there is also a dedicated piece of software available for purchase, entitled SHM for Windows (DP560) which will compute the data once it has been entered from ATT. See Electronic Products and Services for details.

	Why don’t you supply tidal predictions in Word or Excel format?

	Only PDF (industry standard for printing and publishing purposes) and ASCII formats are supplied. All the ASCII files can be opened in either Word or Excel and manipulated as appropriate, however the UKHO cannot give advice and guidance on the use of other software packages for this purpose.

	Can I put your tidal predictions on my website?

	Yes. However, you must restrict the output to only display 7 days (i.e. the current day plus 6 days) at any one time. This accords with the UKHO tidal predictions website ‘EasyTide’ (www.ukho.gov.uk/easytide). The UKHO also welcome links through to the EasyTide website, providing they meet the criteria outlined in UKHO Links Policy. Further details can be found at www.ukho.gov.uk/linksPolicy.

	Are the Harmonic Constants themselves available for purchase?

	No. The UKHO does not release the full sets of Harmonic Constants for any port. However, the “abridged” sets of constants (i.e. those published in Part III of Admiralty Tide Tables and intended for use in the SHM software) are available for licensed use. Please contact UKHO Copyright Section for further guidance, e-mail copyright@ukho.gov.uk.