Hi,
Oh, I see now. Geoserver is always sending the whole +1000 rows long list of
supported SRS/CRS codes in the same order and that can’t be used for guessing
the native SRS. Therefore BBOXes are analyzed. Well, that is a good guess for
Mapserver too because it does create BBOX for the first SRS on the list. Guess
may not be as good with ArcGIS servers, at least the one I checked seems to
like to put EPSG:4326 and CRS:84 boxes always on top of the list.
BTW, ArcGIS even translates “CRS:84” into code “SRS:84” for WMS 1.1.1.
So because WMS stardard has not defined the native SRS it seems to be
impossible to make a perfect guess for all WMS server brands. A possibility to
select manually the preferred SRS that Geoserver is using as native one would
be a good feature sometimes.
-Jukka-
Andrea Aime wrote:
On Mon, Sep 29, 2014 at 9:58 AM, Rahkonen Jukka (Tike)
<[email protected]<mailto:[email protected]>> wrote:
I have not thought thoroughly but my feeling is that WMS clients should not
care about advertised BBOXes but that is probably because I run Mapserver which
believes whatever layer extents I manually write into the mapfile and they are
systematically inaccurate and often totally wrong, I fear. WMS servers send
empty maps very fast if WMS client is sending BBOX which is outside the data
area. However, I can imagine that sometimes, for some servers, there can be
more trouble if client is sending a BBOX-SRS combination that does not work
because re-projection with those values is impossible.
Hi Jukka,
the main reason to guess the native SRS is just an accuracy one, most GeoServer
clients pick the first bbox we publish as the native
one, and if that is correct, you get less distortion in your output, either
because you're doing less resampling operations on your
raster data, or for vector data, because you're avoiding potential datum shifts
that can also incur in severe errors.
The second one is of course the convenience, in Tore's case he's not getting
the full bbox in the form by default, but just half of it
Cheers
Andrea
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