Comparison of AR. Drone quadricopter video and the visual CTLA method for urban tree hazard rating

Abstract

The Parrot AR. Drone 2.0 unmanned aerial vehicle was used to assess the condition of 52 trees using a hazard rating system designed for an urban landscape. AR. Drone hazard ratings were compared to the Council of Tree and Landscape Appraisers (CTLA) method of tree condition based on six variables: Trunk Condition, Growth, Crown Structure, Insect and Disease, Crown Development, and Life Expectancy. For each tree, streaming video from the AR. Drone was captured onto an iPad2 using the AR. Free Flight 2.4 app. The AR. Drone was stable in flight and easy to manipulate and produced video that could be stored for later study. The hazard rating of the trees within the AR. Drone video was compared with the visual hazard assessment of the CTLA method. Comparison of the six variables revealed no statistical difference in the measurements using a Wilcoxon paired-sample test at the 0.05 level of significance. A strong correlation was observed between the two approaches based on Spearman’s rank-order analysis. Results indicate that urban trees can be effectively rated for hazard from a distance using a drone that can reach and assess areas of a tree not accessible or viewable from ground level.