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[CF-metadata] FW: Proposed new standard name: projection_zone

From: Godin, Michael <godin>
Date: Thu, 27 Oct 2011 09:16:09 -0700

In my application, vehicle navigation is done in the WGS84 frame of reference, and the latitude and longitude of every data point is logged. So there's no problem being CF-compliant in the primary data product. I was seeking to generate am auxiliary data product compatible with a legacy plotting package that relied upon UTM coordinates. Since it seems I'm getting no traction on projection_zone, and the auxiliary data products are not widely broadcast -- I'll just make non-CF conforming files.
 
BTW, I do not believe there is any monotonic constraint on the coordinates of a trajectory.

Best, Mike

-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Hedley, Mark
Sent: Wednesday, October 26, 2011 09:48
To: cf-metadata at cgd.ucar.edu
Subject: [CF-metadata] FW: Proposed new standard name: projection_zone


Another potential approach would be to split your data into different data variables, and link each data variable to the required coordinate reference system.

Each data variable could have the same standard_name, unit, etc; an extra custom attribute could be used to indicate the chaining process.

If you use one data variable, it seems to me you run the risk of having major jumps and repetitions in the coordinates, such that coordinate variables, with their monotonic constraint, cannot be used.

mark

-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu on behalf of Kennedy, Paul
Sent: Tue 25/10/2011 16:12
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Proposed new standard name: projection_zone
 
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 Thu Oct 27 2011 - 10:16:09 BST

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