Tree metrology system

A method and apparatus for identifying a number of diameters for a group of trees (206). An unmanned aerial vehicle (236) moves on a route (522) through the group of trees (206) at a height that is configured to allow measurement of the number of diameters for the group of trees (206) by a sensor system (306) associated with the unmanned aerial vehicle (236). Information is generated about the number of diameters for the group of trees (206) using the sensor system (306) associated with the unmanned aerial vehicle (236).