Nearest Neighbor Aggregation in GeoMedia 6.1
Posted by jeffhobbs on June 27, 2007
Started playing with the two new aggregation operators (pipes) in GeoMedia 6.1 today. There appear to be a few bugs, but overall it looks very promising.
For my testing I used the US Sample data set and aggregated the cities and the highways. My summary feature was the cities feature class while my detail feature was the interstates feature class.
The first operator is labeled "are nearest to". From what I can tell (no documentation yet), this operator will aggregate ONLY the first summary graphic to its respective detail graphic. In other words, if I have 20 cities that are near one highway segment (not the overall highway, but the individual segment), then only one city will receive the respective highway number from the highway segment. Looking at the screen shot below, you’ll notice that each highway number (the second column that’s highlighted) has a respective unique identifier (third column), however no unique identifier is repeated for the same highway number.
Now, when comparing this to the second operator, "accumulate nearest", the opposite is true. With this operator EVERY city has a respective nearest highway. As a result, you DO get repeating highway numbers (second column) for each unique identifier.
Now the value…that can be a little harder to understand. I personally have never had a need (that I can think of) for an operator like "are nearest to". Anybody have any ideas?
However with the "accumulate nearest", this to me makes a lot more sense. Often times I’ll want to bulk update a set of geometries in feature class B with information from feature class A. For instance, you might want to update your fire hydrants with the nearest one or two street names. In the past, if you’re an Oracle Spatial kinda user, this can be done at the SQL level. However for those that would rather do it in the client GIS, this makes it a lot easier.
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