look for cells where there are multiple clusters of sightings

[cooperq]

short version:
first pass:
arithmetic mean of lats and lons

get sigma vs. arithmetic mean

if it's too high
it probably requires a multicluster
else
sum signal weight, signal-weighted lat and log

multicluster pass:
iterate through points
if point near-enugh an existing cluster
add point
else
start a new cluster with point