[mapguide-trac] #1392: OGC WMS 1.3.0 Support

[MapGuide Open Source]

#1392: OGC WMS 1.3.0 Support
-----------------------------+----------------------------------------------
   Reporter:  liuar          |       Owner:  liuar   
       Type:  enhancement    |      Status:  new     
   Priority:  medium         |   Milestone:          
  Component:  WMS Interface  |     Version:          
   Severity:  trivial        |    Keywords:  WMS CITE
External_id:                 |  
-----------------------------+----------------------------------------------

Comment(by liuar):

 One significant change in WMS 1.3.0 is the axis orientation. In order to
 align
 with the definitions from the EPSG database, OGC WMS 1.3.0 specification
 reversed the axis sequence for some EPSG code include EPSG:4326. Which
 means for
 some EPSG CRS, the meaning of (x,y) is changed from (lon,lat) to (lat,lon)
 or
 even other orientations. [[BR]]
 [[BR]]

 1) To obtain the axis orientation from a particular EPSG coordinate
 system, CS
 team enhances the Mentor_CS library and provides an API named
 MgCoordinateSystem::GetEpsgQuadrant

 {{{
 // 0    X increases to the East,  Y increases to the North
 // 1    X increases to the East,  Y increases to the North
 // 2    X increases to the West,  Y increases to the North
 // 3    X increases to the West,  Y increases to the South
 // 4    X increases to the East,  Y increases to the South
 // -1   X increases to the North, Y increases to the East
 // -2   X increases to the North, Y increases to the West
 // -3   X increases to the South, Y increases to the West
 // -4   X increases to the South, Y increases to the East
 INT16 MgCoordinateSystem::GetEpsgQuadrant (void)
 }}}

 2) Because different coordinate system has different axis orientation, the
 request parameter boundingbox (coord1,coord2,coord3,coord4) may indicate
 different area.[[BR]]
 Therefore, after getting the quadrant of the EPSG coordinate system, it's
 necessary for MapGuide to process boundingbox
 (coord1,coord2,coord3,coord4) to
 the normal format (minX,minY,MaxX,MaxY). There are 3 methods to help
 handling
 the boundingbox axes orientation, and these method are implemented as
 utility
 methods[[BR]]

 {{{
 class MgWmsMapUtil
 {
     public:

     ...

     // Handle the CRS(SRS) which have their axis orientation changed
     static void ProcessBoundingboxAxes(STRING sSrs, REFSTRING bbox);
     //Help method to swap coordinates in boundingbox
     static void SwapCoords(double* coord);
     //Help method to make coordinates about-turn
     static void SwerveCoords(double* coord1, double* coord2);
 }
 }}}

 3) If the required wms version is higher than 1.3.0. then the request
 parameter
 boundingbox should be processed at three different places. When the
 request
 parameters are initializing in two MgHttpRequestResponseHandler:
 MgHttpWmsGetMap
 and MgHttpWmsGetFeatureInfo, and when it's need to validate the "GetMap"
 request
 request parameters in MgOgcWmsServer. Note that because the
 ValidateMapParameters is invoked by ValidateGetFeatureInfoParameters, so
 it's
 not necessary for ValidateGetFeatureInfoParameters to process the
 boundingbox
 axes.

 {{{
 void MgHttpWmsGetMap::InitializeRequestParameters(MgOgcWmsServer& oServer)
 {
         ...

         if(m_version >= _("1.3.0"))
     {
         MgWmsMapUtil::ProcessBoundingboxAxes(m_crs,m_bbox);
     }

         ...
 }

 void MgHttpWmsGetFeatureInfo::InitializeRequestParameters(MgOgcWmsServer&
 oServer)
 {
         ...

         if(m_version >= _("1.3.0"))
     {
         MgWmsMapUtil::ProcessBoundingboxAxes(m_crs,m_bbox);
     }

         ...
 }

 bool MgOgcWmsServer::ValidateMapParameters(MgStringCollection*
 queryableLayers)
 {

         ...

         if(sVersion >= _("1.3.0"))
     {
         CPSZ crs = RequestParameter(kpszQueryStringCrs);
         if(crs == NULL || szlen(crs) == 0)
         {
                 crs = RequestParameter(kpszQueryStringSrs);
         }
                 MgWmsMapUtil::ProcessBoundingboxAxes(crs,sBBox);
         }

         ...
 }
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/mapguide/ticket/1392#comment:6>
MapGuide Open Source <http://mapguide.osgeo.org/>
MapGuide Open Source Internals