My source data is GML, and is based upon a network model of
RoadLinks connected by RoadNodes. Each RoadLink feature has an
attribute which holds the id of the 'start' RoadNode for the link,
and likewise for the 'end' RoadNode. So far so simple.
However, the source data includes nodes where one wouldn't
necessarily expect/want them, for example at the point where the
road on an overbridge crosses a different road underneath. To
distinguish between such roads and therefore enable navigation of
the network data, an extra couple of attributes are included in the
RoadLink feature, namely StartNodeGradeSeparation and
EndNodeGradeSperation. At a given node, traffic can only physically
navigate between links if they have the same grade separation value
(typically these values run 0,1,2,...). Thus, in my example of an
overbridge, you would have 4 links referencing the same node (some
as start node, some as end node), but 2 links would have a grade
separation value of 0 for their appropriate node, and the other 2
would have a grade separation value of 1.
If you're still with me / awake, what I'd like to do is one or both
of the following:
1. Pick out all such 'unwanted' nodes, i.e. determine all RoadNode
features that are referenced by >1 RoadLinks such that the number of
different grade separation values is >1. This would, for example,
allow me to draw such nodes in a different colour on a map.
2. For every such node, merge each pair (assuming that there are
exactly two) of RoadLink features which are attached to the node
with the same grade separation value into a single RoadLink feature.
In other words, I'd like a facility to get rid of the unwanted nodes.
After much head-scratching and a spaghetti of transformers on my
canvas, I'm no nearer to solving this - if indeed it's the kind of
thing for which it's appropriate to use FME.
If anyone can make sense of this without diagrams and come up with
an answer, consider me impressed.
Simon
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