Why are tides important in satellite mapping and managing our coasts?

  • Jonathan Hendry, Bristol based Marine Data Analyst for TCarta created this month’s blog explaining how knowledge of tides,  Satellite Derived Bathymetry and Topographic Bathymetry Models can be used in many applications. Jonathan explains….

    Why are tides important in satellite mapping and managing our coast?

    By Jonathan Hendry

    Answering this question depends who we are and very importantly where we are. As a Maritime Civil Engineer, working within Newfoundland Canada I might see, over the course of a day, a 16.3 metre difference in the water height within the Bay of Fundy. Without knowledge of the tides I risk flooding my multi-billion dollar port. However, if I lay back in my linen deckchair amongst the Bahamas shells I may mistake a larger than usual wave for the 30cm rise and fall in sea level as the tide gently grazes my Long Island iced tea - that is now more tea than ice in the golden sun.

    The important take home message is that for every location there is a different tide. The tides significance is a function of the tidal magnitude, vulnerability of population and the accuracy of the tidal information.

    As my colleague Ross stated in his blog last month Satellite Derived Bathymetry, ‘What is Satellite Bathymetry?’  is all about uncertainty of data. But surely a tide is a tide is a tide, it's a single value...right? However, at TCarta our chosen satellite images are treated at tidal snapshots. Hence to deliver excellent water depth data (in the form of Satellite Derived Bathymetry) we need to know that tidal depth difference between each satellite image.

    TCarta uses the standardised value of Chart Datum (CD) (approximating to the Lowest Astronomical Tide (LAT)) for Bathymetry products and in bathymetric Electronic Nautical Charts (bENC) helping ship captains/skippers to plan their routes through treacherous waters and avoid the dangers of obstacles like sand banks. But tide stations can be few and far between especially in areas in the Pacific Ocean. So to ensure correct tidal corrections at these far off dreamy beaches we need sophisticated, well calibrated and thoroughly tested models. We at TCarta pride ourselves on affordable excellence for all our data.

    Why are tides important in satellite mapping

    With this in mind we can test for the most accurate tidal curve. These curves (showing the tidal height at a given time) take into account not only the Moon and Sun  (the most powerful drivers of our tides) but also Jupiter and many other planets as well as the actually morphology of the specific region the satellite image is taken at. In summary we ensure every tide is specifically defined to a given area so our project’s data is accurate and honestly as good as technology may allow.

    Other articles related to this subject:

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