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Re: [udig-devel] GML loading - over the top?
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Jody,
At 19:45 12/09/2007, Jody Garnett wrote:
Your file however does not contain all the information needed; often
for a roadMember you will end up with a networkMember refered to by
an xlink:href='#xxxxxx' - and that ID is not used anywhere in the
file. What are you expecting us to do in this situtation?
I'm not sure really. It could perhaps be that the reference is in a
another .gml file (they typically send lots of chunks, ranging in
size from a few k to a few megabytes) - we might have 60 or more GML
files for an area with a population of 100000 people.
Some of these references would appear to be in different layers, for
example this one:
<osgb:referenceToTopographicArea
xlink:href='#osgb1000001795448371' />
The 'topographic' layers from OS are generally supplied separately as
far as I am aware. The layers we care most about are the topological
ones: ITN and RRI, and the Address information. These are needed for
routing purposes. Topographic layers are only needed to draw pretty
maps (clearly useful, but not essential to us).
--
But, more generally, aren't there always going to be dangling
references at the edges of any topologically sound data of, say, a
road network. This particular data contains not just geometries for
visualisation of the roads, but also the connectivity information
(this road has these 2 junctions at its ends, those junctions connect
to these other roads, etc). This means at the edges one will surely
always have unknown references?
Do take all the above with a pinch of salt, since I've not really
digested the GML spec nor OS's use of it. (and I was hoping not to,
really... ;-)
The freeware Snowflake GML viewer manages to load all this data and
visualise it very nicely, however, so I can at least assure you the
data is good!
cheers,
Vince.