Hi Mike,
We regularly have this issue at our shop. We attempted to preserve UTM
coordinates across long distances such as fibre cables across the
pacific, but if you have a very large spatial set, which spans multiple
CRS' it really is better to use a global CRS such as WGS geographicals.
UTM Projections are great for local grids but really do not scale well.
Hope this helps
pk
-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu
[mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Godin, Michael
Sent: Tuesday, 25 October 2011 10:32 PM
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Proposed new standard name: projection_zone
Hello Mark,
While the WKT format certainly can describe the mapping of one zone
well, I am trying to represent trajectories that cross multiple zones.
It's not clear how that can be done in the context of the proposal.
It's the same difficulty encountered with the current set of mapping
attributes: they define one and only one projection for the dataset.
Hence, I am proposing the new standard name "projection_zone" to allow a
trajectory to exist in multiple UTM zones, each of which has its own
well known and universally understood definition.
I had earlier suggested a new grid_mapping_name attribute value:
universal_transverse_mercator -- this may not be necessary since a value
of "transverse_mercator" in a trajectory file that includes the triplets
of projection_zone, projection_x_coordinate, and projection_y_coordinate
should be adequate for indicating a UTM trajectory.
Mike
-----Original Message-----
From: Hedley, Mark [mailto:mark.hedley at metoffice.gov.uk]
Sent: Monday, October 17, 2011 04:20
To: Godin, Michael; cf-metadata at cgd.ucar.edu
Subject: RE: [CF-metadata] Proposed new standard name: projection_zone
Hello Mike
there is a ticket open on the TRAC system proposing the use of OGC WKT
to describe coordinate reference systems:
https://cf-pcmdi.llnl.gov/trac/ticket/69
Would this give you the vocabulary you require?
mark
-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu on behalf of Godin, Michael
Sent: Tue 11/10/2011 14:35
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] Proposed new standard name: projection_zone
This has a corresponding new grid_mapping_name attribute value:
universal_transverse_mercator
This was last discussed in depth in 2005, and I believe the resolution
was that the attributes corresponding to the "transverse_mercator"
mapping were perfectly adequate to describe the projection within any
given zone.
However, I am trying to represent the trajectory of a vehicle that
typically crosses zones, and there does not seem to be a satisfactory
means for documenting a multi-zone trajectory with the current attribute
set. Granted, specifying only the UTM zone is much less descriptive
than the full set of transverse mercator mappring attributes, but UTM
really is pretty well universally understood, and I'd be surprised to
find a mapping library that can't handle a UTM zone integer as the full
description of the mapping.
Hence, I propose:
standard_name: projection_zone, units: 1
Best, Mike
_____________________________________________
Michael A. Godin
Software Engineer
Monterey Bay Aquarium Research Institute
Phone: 413-206-6444
http://www.mbari.org <
http://www.mbari.org>
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Received on Tue Oct 25 2011 - 09:12:40 BST
