Winkler published  the methodology of a simple, accurate and direct dissolved oxygen analytical procedure in 1888. Since that time, the analysis of dissolved oxygen levels for water has been key to the determination of surface water. The Winkler method is still one of only two analytical techniques used to calibrate oxygen electrode meters; the other procedure is based on oxygen solubility at saturation as per Henry's law.
There are two recognized  methods for the measurement of dissolved oxygen for  BOD and a number of other methods not currently internationally recognised as standard methods