On Tue, Aug 14, 2012 at 8:24 AM, Andrea Aime
<[email protected]> wrote:
>> > The WCS spec uses the urn: form, urn:ogc:def:crs:EPSG::4326,  that
>> > mandates
>> > the data to be expressed in lat/lon order, GeoServer respects that to
>> > the
>> > letter.
>>
>> Do you mean that the GetCoverage result output is rotated for 4326?
>> That is exagerated IMO.
>
> It is rotated yes. It seems to me no more exagerated than having coordinates
> flipped in vector data. Very inconvenient with the existing tools, but
> that's how OGC wants it
> and it has been inconvenient for WFS as well.

I think that there is a difference between vector or ordered list of
coordinates and raster. Raster does not have any order of axis, it has
horizontal and vertical direction, but why should be the horizontal
considered to be the first (and thus used as second ...)?

>> >> The result with 1.1.1 is also larger by 1 pixel in each direction
>> >> (1.0.0 works OK), is it taken into account that 1.1.1 grid is using
>> >> cell centers, not edges?
>> >
>> > OGC mandates cell centers as the one and only way to deal with raster
>> > data
>> > as far as I know, I believe we should be using it on both WCS versions
>> > but
>> > I'm not sure, they were implemented by two different people and the code
>> > paths are quite different.
>>
>> I was wrong, GeoServer gives result smaller by 1 pixel if bbox is
>> defined  by "pixel" centers (grid points), so I have to use bbox
>> extended by 1 pixel, the same like WMS 1.3 which is not what WCS 1.1
>> requires AFAIK.
>
> Can you cite the parts of the spec that makes you think so?

Version: 1.1.2, Version 1.1 Corrigendum 2 release, Document: 07-067r5

7.6.3
Treatment of edge grid points

The spatial extent of a grid coverage extends only as far as the
outermost grid points contained in the bounding box. It does NOT
include any area (partial or whole grid cells or sample spaces) beyond
those grid points.

NOTE
This bounding box is NOT the extent sometimes considered, which also
includes rectangular sample spaces (pixels) centered on the outermost
grid points – as indicated in Subclause 7.3.3 6 of WMS 1.3 [OGC
04-042]. Such pixel extents are often poor approximations of the
sensor physics / grid data collection process.

EXAMPLE
The extent of a global data set in WGS84 geographic decimal degrees
with a grid spacing of 1.0 degree might be expressed as a
WGS84BoundingBox with LowerCorner and UpperCorner longitudes of
(respectively) -179.5 and +179.5, or -179.0 and +180.0, when that data
set is not considered continuous (interpolatable) across the
antimeridian at 180 degrees. When that data set is interpolatable
across the antimeridian, the LowerCorner and UpperCorner longitudes
(respectively) might be -180 and +180 (with redundant first and last
columns of data), or –INF and INF.

Radim

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