http://wiki.openstreetmap.org/wiki/Proposed_features/Tag:man_made%3Dtower
http://wiki.openstreetmap.org/wiki/Tag:power%3Dtower
http://wiki.openstreetmap.org/wiki/Tag:aeroway%3Dcontrol_tower
http://wiki.openstreetmap.org/wiki/Proposed_features/measurement_station
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HB: probably based on fields.tower_use

Glen: Filled in the fields based on the types given. Defaults to man_made:tower if we don't have any further info