* The algorithm is implemented as envelope on envelope overlays rather than
* complex polygon on complex polygon overlays.
* Spatial relevance scoring algorithm:
* <DT>queryArea</DT> <DD>the area of the input query envelope</DD>
* <DT>targetArea</DT> <DD>the area of the target envelope (per Lucene document)</DD>
* <DT>intersectionArea</DT> <DD>the area of the intersection between the query and target envelopes</DD>
* <DT>queryTargetProportion</DT> <DD>A 0-1 factor that divides the score proportion between query and target.
* 0.5 is evenly.</DD>
* <DT>queryRatio</DT> <DD>intersectionArea / queryArea; (see note)</DD>
* <DT>targetRatio</DT> <DD>intersectionArea / targetArea; (see note)</DD>
* <DT>queryFactor</DT> <DD>queryRatio * queryTargetProportion;</DD>
* <DT>targetFactor</DT> <DD>targetRatio * (1 - queryTargetProportion);</DD>
* <DT>score</DT> <DD>queryFactor + targetFactor;</DD>
* Note: The actual computation of queryRatio and targetRatio is more complicated so that it considers
* points and lines. Lines have the ratio of overlap, and points are either 1.0 or 0.0 depending on wether
* it intersects or not.
* <p />
* Based on Geoportal's
* <a href="http:>
* SpatialRankingValueSource</a> but modified. GeoPortal's algorithm will yield a score of 0
* if either a line or point is compared, and it's doesn't output a 0-1 normalized score (it multiplies the factors).