The calculations of distance appears to be off.
Note: "The radius of the sphere to be used when calculating distances on a sphere (i.e. haversine). Default is the Earth's mean radius in kilometers (see org.apache.solr.search.function.distance.Constants.EARTH_MEAN_RADIUS_KM) which is set to 3,958.761458084784856. Most applications will not need to set this."
The radius of the earth in KM is 6371.009 km (≈3958.761 mi).
Also filtering distance appears to be off - example data:
45.17614,-93.87341 to 44.9369054,-91.3929348 Approx 137 miles Google. 169 miles = 220 kilometers
Nothing shows. d=285 shows results. This is off by a lot.
SOLR-1568 Implement Spatial Filter