Haaring, P.A. (MIA-RIKZ) wrote:
> Dear John,
>
> We would be most happy if this would be added.
> In the Netherlands we use it along our National grid.
> There is an additional problem we both use it based on the ED50 and
> the WGS84 ellipsoide.
> How would you code this into the metadata?
>
> Pieter Haaring
>
> Ministry of Transport, Public Works and Water Management
> National Institute for Coastal and Marine Management (RIKZ)
> P.O. box 20907 / 2500 EX The Hague / The Netherlands
> Tel:+31703114570 Fax:+31703114321 Email: p.a.haaring at rikz.rws.minvenw.nl
>
It was my understanding that each UTM zone has a standard ellipsoid. I
am not sure if thats the case or not, does anyone know? In any case, it
appears that other ellipsoids are needed, so one should be able to
specify them, so we should allow an additional parameter, eg:
zone="13S";
ellipsoid="WGS84";
Issues:
1. If there is standard ellipsoid for each zone, it would be nice if
the ellipsoid parameter could be optional, since many may not know what
to put there.
2. We probably want a controlled set of ellipsoid names (?)
3. It appears that one only needs to specify north or south
hemisphere, that one doesnt need the A-Z part. Anyone know if thats
really true?
>
> -----Oorspronkelijk bericht-----
> Van: John Caron [mailto:caron at unidata.ucar.edu]
> Verzonden: 21 oktober 2003 21:46
>
> Aan: CF-metadata
>
> Onderwerp: [CF-metadata] UTM projections
>
>
> How do people feel about adding Universal Transverse Mercator (UTM) as a
> Grid Mapping? We are talking to someone who wants to use UTM, and we'd
> like to steer them to CF.
>
> As I understand it, UTM uses the ellipsoidal Transverse Mercator
> projection The earth is divided up into approximately 60 x 24 "zones",
> each with specific projection parameters. There are a number of
> complications, like the fact that the reference ellipsoid may differ
> between zones, and near the poles it in fact switches to a polar
> stereographic projection.
>
> All of this complicates the client that has to implement it, but in
> terms of CF coding it would be just a matter of specifying the UTM
> zone, eg:
>
> grid mapping name = UTM
>
> Map parameters:
>
> zone - eg "13T"
>
> A client has to have a table that maps the zone name into the right
> Transverse Mercator (or Polar Stereographic) projection parameters. The
> alternative would be to make the user use the Transverse Mercator (or
> Polar Stereographic) projection directly, and figure out the right
> paramters themselves.
>
>
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>
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Received on Wed Oct 22 2003 - 10:06:44 BST
