[mapserver-users] WFS version and axis order

[Rahkonen Jukka]

Hi,

Unfortunately axis order in WFS 1.1.0 (or in GML3) is complicated.


> I need a second option so I can respond to a customer regarding their concerns of using our > WFS services.  Their concern is mainly confidence and the ability of moving forward.  As you > know in the WFS version 1.1 the axis order switched.

Too genaralised to say so. There are systems which have officially easting-northing axis order, like WGS84 UTM zones, and for them WFS 1.0.0 and 1.1.0 must behave similarly.


> These are their assumptions:

> * WFS v 1.0 will serve data in lon, lat order
> * WFS v 1.1 can serve data in lon, lat and lat, lon as well

The meaning of the standard is "No", each projection has one fixed, official and correct axis order. In real life WFS 1.1.0 servers may behave differently.  For example Geoserver, TinyOWS and probably deegree are using the WFS 1.0.0 style axis order if srsName is given in short format EPSG:4326.  When using long format srsname=urn:ogc:def:crs:EPSG::4326 servers are trying to use the correct order.


> MapServer-Users, Is there way in WFS v1.1 to maintain the lon,lat order for every projection, client request parameter or server configuration?


I think that if you ask for GML2 outputformat then the response should be lon-lat (easting-northing) always.


> * We need a way to clearly define how to build BBOX for request (lat,lon or lon,lat) and in what order will be the response – I think that > order should be consistent for request and response.

> MapServer-Users, the last bullet refers to the relationship between BBOX and the WFS versions.  > Please confirm BBOX will always be of the contruct: minx,miny,maxx,maxy


Yes, but the meaning of x and y varies :)  Order in BBOX axis follows the official definition of the projection. In addition, according to the WFS 1.1.0 standard BBOX=minx,miny,maxx,maxy defaults to EPSG:4326 projection and not to the default output projection. For being unambiguous for all WFS servers with WFS 1.1.0 the BBOX should be given with five parameters where the last one defines the projection of BBOX. However, not all WFS servers honour these rules or even understand the fifth BBOX parameter.  It gets a bit more complicated when OGC Filters are used instead of Key-Value pair BBOX because then the BBOX defaults to the default output projection. Better to give the exact srsName always with Filters too.


> Thanks in advance,

I promise you and your clients will get mad with this.

-Jukka Rahkonen-
> Randy