However, this is defined differently in different countries and situations. In many countries the diameter has been measured usually at 1.3 metres above ground.[1][2] In some countries, such as Australia, New Zealand, the United States, Burma, India, Malaysia, and South Africa, breast height diameter has historically been measured at a height of 1.4 metres at some times, but because of much active research into allometrics that are being applied to trees and forests, the convention of 1.3 m is now more appropriate. Previously 4.5 ft (1.37 m) was used.[3] The height can make a substantial difference to the measured diameter.[4] Ornamental trees are usually measured at 1.5 metres above ground.