Waikato Regional Council is about to start its annual monitoring of effluent management on dairy farms.
Compliance Manager Rob Dragten says helicopters will fly over about 1000 properties, which have been randomly selected from the 4000 dairy farms in the region.
Aerial monitoring is part of the council's effort to reduce nitrate pollution.
Mr Dragten says the results from a survey of more than 800 farms in 2010-11, showed 12% significantly breached the council's effluent rules, compared with 27% the previous year.
