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#107: CF Data Model 1.7
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Reporter: markh | Owner: cf-conventions@…
Type: task | Status: new
Priority: medium | Milestone:
Component: cf-conventions | Version:
Resolution: | Keywords:
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Comment (by davidhassell):
Hello,
Jonathan, Jon and I have taken advantage of our geographic colocation and
have been discussing the Transform construct offline. As a result, we'd
like to propose the replacing it with a "Geolocation construct", described
below. The geolocation construct is similar (but not identical) to the
transform construct, and we hope that its definition is much clearer.
We'll be very interested in your comments.
All the best,
David
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'''Georeference construct'''
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A georeference construct provides information needed to locate spatial
dimension and auxiliary coordinates within a frame of reference relative
to the planet.
Whilst the spatial coordinate constructs themselves serve to locate the
data within the domain of the field, some applications may require more
information about the relationship of the domain to a planetary reference
frame. Moreover, some of the information may be identical for multiple
constructs and therefore needs to be defined only once.
A georeference construct contains
* An unordered collection of the field's dimension and auxiliary
coordinate constructs to which the georeference construct applies.
* Scalar parameters (which may include descriptive strings), other
dimension or auxiliary coordinate constructs of the field, or other field
constructs; all of which provide information about the frame of reference.
The most common purposes of a georeference construct are
* To specify the relationship between vertical coordinates which are not
geolocated and coordinates of height (with respect to some geophysically
located surface) or pressure (which is a proxy for
height).
* To specify the relationship between horizontal coordinates which are not
geolocated and a logitude-latitude coordinate system with a particular
reference ellipsoid for the shape of the planet.
The functions of the CF-netCDF attributes formula_terms and grid_mapping,
which describe the locations of spatial coordinate variables (CF
Appendices D and F), correspond to georeference constructs.
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Ticket URL: <http://kitt.llnl.gov/trac/ticket/107#comment:55>
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