Mapping an annual weed with colour-infrared aerial photography and image analysis

Silverleaf sunflower (Helianthus argophyllus, Torr and Gray) is an annual weed found on rangelands in south and southeast Texas. Colour-infrared aerial photography and computer image analysis techniques were evaluated for detecting and mapping silverleaf sunflower infestations on a south Texas rangeland area. Supervised and unsupervised image analysis classification techniques were used to classify photographs from two study sites. Supervised classification of the two photographs showed that silverleaf sunflower had mean producer's and user's accuracies of 95.2% and 91.3%, respectively. Unsupervised classification of the two photographs had mean producer's and user's accuracies for silverleaf sunflower of 65.7% and 80.1%, respectively. These results indicate that the supervised technique is superior to the unsupervised technique for mapping silverleaf sunflower infestations using colour-infrared aerial photos.