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    Re: Land or sea
    From: Nicolàs de Hilster
    Date: 2009 Oct 12, 14:25 +0200

    Wolfgang.Hasper{at}web.de wrote:
    > Dear Navlist members,
    >
    > I am currently working with climate data given in a database for the whole world.
    > Resolution is 1 deg latitude/ 1 deg longitude cells which makes 180 * 360 cells overall.
    > Since for every cell a number of year's data is available it is a lot of material.
    > My work requires only data for those cells on land.
    >
    > Does anybody know a quick and easy way to determine which cells are relevant (i.e. on land, not ocean)?
    > This should be a standard procedure for many purposes, however I couldn't find anything helpful yet.
    >
    >   
    First of all you need a dataset containing the world's coastlines, which 
    can be found here:
    http://gcmd.nasa.gov/records/GCMD_Signell_extractor.html
    or here:
    http://www.pdc.org/mde/full_metadata.jsp?docId={32F5F3B8-1CF1-48C5-9B81-57885C0CA448}
    
    Then you need to built yourself or download some software that that 
    create poligons from the coastline data and uses it to clip your climate 
    data. Routines and software for this can be found here:
    http://www.cs.manchester.ac.uk/~toby/alan/software/
    
    Or even easier: download the picture found at 
    http://www.ngdc.noaa.gov/mgg/shorelines/shorelines.html, which shows you 
    the world coastlines at the resolution you require (I also attached it 
    to this post). Then fill in all the land masses (in order to get 
    black=land and white=ocean/sea instead of black=coastline) and use the 
    image as a mask for your application.
    
    hope this helps,
    Nicolàs
    
    
    
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