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How can I utilise measured tide data available via the Channel Coastal Observatory website?

Posted 03/06/2016 14:00 by Anonymous

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Tidal data for many parts of the UK is freely available via Channel Coastal Observatory (CCO) website. This data may prove valuable to your coastal study, for example to compare measured water levels in relation to flood defences. The following steps will help you obtain and utilise this data within SANDS: 1) Get the data via the Channel Coastal Observatory website www.channelcoast.org/ -Select 'Map Viewer & Catalogue' then 'View Maps & Search Data Catalogue' -Login (or register/login) -Navigate the map and highlight the area of interest -Select 'Next' (all data for your selected area will be summarised) -Select the data required (in this case Tide) -Select 'Next' and 'Add all results to basket' -Select 'View your basket' and 'Download basket' -Save the zip file to your system 2) Import the data, into SANDS -Unzip the downloaded data (Tip, in the interests of good housekeeping create and unzip into a new 'Tide data' folder under the SANDS project folder) Note that in addition to the actual 'tide data' other files are also downloaded including metadata that provides valuable background information. -If required setup a location to associate the data to (Tip, the tide buoy name, type and location coordinates are all provided in the metadata file, use the information provided. And why not link this document to your tidal station for future reference) -From the SANDS window, select 'File' then 'Import/Export data' then scroll down and select 'CCO Tide Data' (under Import CCO Format Data) -Select the appropriate location you wish to associate the data to and 'Add File..' to select the files for import, next press 'Import All' (Note, you have the option to import the data in Ordnance datum or Chart datum) -The newly added tidal data will now be visible via the 'Graph' (e.g. Water Level and Surge Residual) 3) Check the data, in SANDS (Tip, always check data before undertaking any analysis) -From the SANDS window, select the 'Graph' button, select the imported data then plot (Tip, set the plot range to cover the date extent of the data you have imported) -Perform a visual check of the water level data to ensure the range of the data looks sensible (Tip, compare to known levels e.g. levels quoted in the Admiralty tide tables) -Explore and understand any data that is out of range. Tip, any questionable data is flagged in the data files and explained in the metadata e.g. Flag can be 1 (correct value), 2 (interpolated), 3 (doubtful), 4 (isolated spike or wrong value), 5 (correct but extreme), 6 (reference change detected), 7 (constant value), 8 (out of range) or 9 (missing) 4) Edit the data, in SANDS (if required/optional) -From the From the SANDS window, select 'Time Series' and then 'Edit Time Series Data', select the appropriate tab (Water Level Data) and select the imported data. -Data can be filtered by selecting any of the headers e.g. Date, Water Level Data, Residual Surge and Data Flag (Tip, a 'Custom' filter can be used to filer data within a specified range. An easy way to filer questionable data is via the Data Flag e.g. Flag 8 is data out of range -Filtered data can be edited or deleted using the edit tools at the bottom of the 'Edit Time Series Data' window. Note that it may be preferable to edit or remove a value that is known to be out of range, note that values set to 999 will be retained the dataset but ignored by SANDS. If required all filtered data can be deleted by right clicking the mouse and selecting 'Delete Filtered Data Set'. 5) Make good use of the data, in SANDS. The four steps above describe how tide data can be downloaded, imported, checked and edited, after these procedures the data should be ready to use. Some examples of how the tidal data can be used within SANDS are noted below: -Compare with corresponding wave data to explore the relationship -Compare with flood defences or beach profiles -Extremes analysis, to examine the highest water levels and estimate the likelihood of occurrence -Harmonic analysis, to enable tidal predictions -Fill gaps in recorded tidal data with predicted data -Extend the limits of recorded tidal data with predicted data -Use tidal data for wave transformations -Export tidal data merged with predicted data to 'gap fill' or 'extend the range' of the recorded data at user specified interval (e.g. for usage in models) -Export tidal data merged with predicted data to 'gap fill' or 'extend the range' of the recorded data at user specified interval and match to wave data (e.g. for usage in models

Tidal Predictions

Posted 02/04/2015 10:53 by Anonymous

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The SANDS team have recently been asked if tidal predictions can be produced in the absense of any recorded data? Yes, but this requires the input of the appropriate tidal constituents E.g. as provided in the Admiralty Tide Tables (published by the UK Hydrographic Office) Note the values are added under 'Timeseries', 'Tidal Constituents' Note, if a suitable recorded/measured data was available at at location the 'Tidal Harmonic Ananlysis' fuction may also be of use here I.e.to extract the constituents from the timseries and store them in SANDS automatically.

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