Thanks to Heather North who has passed on this link to where we can buy Diameter Tapes [http://www.geosystems.co.nz/Category/67,11,57/Diameter-Tapes.aspx]. This is the best (most efficient and accurate) tool for measuring the growth of our trees.
The tape gives you a diameter measurement rather than the circumference. Remember, we are measuring trees at 600mm above ground level. Use the webform to send in your data so we can add it to the benchmark project.