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) <jukka.rahkonen@…486…> 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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Ing. Andrea Aime
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