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Frank Warmerdam wrote:On 6/22/05, John Caron <caron@xxxxxxxxxxxxxxxx> wrote:I am realizing that striped.nc also has irregularly spaced vertical coordinates. I was thinking that didnt matter, but now im realizing that i cant use a RectifiedGrid like the one below. Can anyone give me an example of how it should be changed to accomodate an irregular vertical coordinate?John,To the best of my knowledge there is no GML well defined mechanism to describe such a grid. Please describe to the list if you find a way of doing so.
That's correct - the definition of the RectifiedGrid element follows ISO19136, which specifies grids with constant spacing along each axis. There is just one offsetVector per dimension.
The ISO 19123 ReferenceableGrid is a more general object, which maps grid coodinates (i.e. integer coordinates) to an external corodinate reference system, but it is defined in terms of operations only, with nolimitation on how it might be implemented (function, lookup, etc). For obvious reasons, this is not implemented in GML
In order to specify a regular grid with non-constant offsets, a newspecialization of CV_Grid/gml:Grid would be required. Not hard conceptually - just replace the single offsetVector on each axis with an ordered list of vectors. (Of course there are various kinds of constraints you might want to apply - e.g. are all vectors on one axis are parallel, or not?)
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