indexes on float8 vs integer

Anyone got any insight or experience in the speed and size of indexes on Integer(4 byte) vs float (8byte). For a project that I'm on, I'm contemplating using an integer for:

Latitude
Longitude

In a huge, publically searchable table.

In the INSERTS, the representation would be equal to:

IntegerLatOrLong = to_integer( float8LatOrLong * to_float(1000000) );

This would keep it in a smaller (4 bytes vs 8 byte) representation with simple numeric comparison for indexing values while still provide 6 decimals of precision, i.e. 4.25 inches of resolution, what google mapes provides.

I am expecting this table to be very huge. Hey, I want to be the next 'portal' :-)
Dennis Gearon

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