On Tue, May 31, 2011 at 5:19 AM, Chris Holmes <cholmes@anonymised.com> wrote:
Looks great. A few small questions - how does this interact with the
time.ftl and height.ftl KML templates?
Are you going to use templates for the configuration? Or just select an
attribute which must be a time or elevation? The .ftl's had a nice small
advantage of being able to do some formatting on the fly.
The proposal ignores KML solid, we are not going to touch or interact in
any way with it. This means if the time/elevation attributes happen to be the
same as the ftl the user will have to configure it twice.
Mind though, the behavior of the two is different different, if you don't say
anything once time is configured you'll get back a point in time, the
features that have the
latest time value, not the entire series.
Same goes for elevation, you get back features with a certain default value,
not the entire set.
So it's safe to say that you probably don't actually want to enable
TIME/ELEVATION
WMS behavior on data destined to GE animations unless the queries are
also changed to use TIME and ELEVATION KVP parameters to select an
interval.
That said, if someone maintaining KML land wants to pick them up from
the configuration
and use them when the ftl is not around, it should not be too hard, I guess
a new level of indirection masking whether the current value comes from
a ftl file or an attribute name would be needed.
And how will people select units for the elevation?
Units are ignored like in any other parts of GeoServer as well (think all
distance related filters, none of them deals with unit).
Time wise the WMS specification has just one unit, ISO8601, so we are
going to stick with it statically.
Elevation wise, in theory we could make a elevation unit chooser, in practice
that's too hard now.
Elevation units are expressed referring to a EPSG code for a vertical datum.
EPSG:5030, the sample value reported in the WMS spec would not even
decode property if you tried (and you would not be able to
use the CRS class too, you'd have to get the authority factory and cast it
to AbstractAuthorityFactory to just try.).
We'd have to first improve the referencing subsystem and then make a
popup chooser like for the CRS one, while we have the abilities to do that,
it bring us beyond the funding we have available at the moment.
So for the moment the proposal will advertise units ISO8601 for
time and EPSG:5030 for elevations.
However the way we're going to develop it will make it possible to add
the selectable vertical datum as a new attribute in a second time, as
resources to do so show up.
Cheers
Andrea
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Ing. Andrea Aime
GeoSolutions S.A.S.
Tech lead
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55054 Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 962313
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