Hi,

Inspired by the "Get Height values fast" discussion I started to dream. The WMS 
GetFeatureInfo is nice tool for getting an answer to question "What's here". 
Unfortunately it is designed to work on top of a map that has previously 
captured from WMS and even it is possible to construct working queries as 
Andrea wrote, they are ugly. That made me to dream that it would be cool if all 
the WMS server projects under the OSGeo umbrella (Geoserver, Mapserver, 
deegree, QGIS Mapserver, MapGuide) would start to support GetFeatureInfo 
requests by plain coordinates in a common  way.

The request could look a much like the Standard GetFeatureInfo, but simpler. M 
means mandatory, O optional parameter.

VERSION=                M       
REQUEST=GetFeatureInfo  M       
QUERY_LAYERS=   M
INFO_FORMAT=    M
SRS or CRS=             M
LON_E=          M       longitude or easting of the queried point in given 
SRS/CRS, 
LAT_N=          M       latitude or northing of the queried point in given 
SRS/CRS
FEATURE_COUNT   O
EXCEPTIONS=             O
BUFFER          O 

Nothing special there. LON_E and LAT_N are as they are to prevent the struggle 
about the axis order. Order of the parameters would not matter. Common 
parameter for defining the buffer would be needed or otherwise it would be hard 
to hit points and linear features.

Another extension could be a profile query tool. Most typical use case would be 
to read a height profile along a line from a DEM layer.  The query would take 
in the line in for example WKT format and the relation which means the distance 
between returned height profile points is units of the SRS/CRS. Example:

REQUEST=GetProfile
PROFILE=LINESTRING(3413306 6974122, 3413316 6974132)
RESOLUTION=10
LAYER=
SRS/CRS=
INFO_FORMAT=

I do not believe so much that this idea will come true but I think that both 
query types could have real use cases.

-Jukka Rahkonen-

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