Runs obis_spue_sql() at a fixed resolution and returns, per effort cell,
the target and effort record counts and their ratio.
Arguments
- con
connection from
obis_store_connect().- num_aphiaid
target-taxon AphiaID(s) (numerator subtree).
- den_aphiaid
effort-taxon AphiaID(s) (denominator subtree); typically a higher-order taxon such as the target's parent class.
- res
H3 resolution (1-7).