Large-area mountain pine beetle infestations: Spatial data representation and accuracy

Point data generated from helicopter surveys are used to determine the location and magnitude of mountain pine beetle infestations. Although collected for tactical planning, these data also provide a rich source of information for scientific investigations. To facilitate spatial research, it is important to consider how to best represent spatially explicit mountain pine beetle infestation data. This paper focuses on the spatial representation of point-based aerial helicopter surveys, which can be difficult to represent due to issues associated with large data quantities and data uncertainty. In this paper, the benefit of using a kernel density estimator to convert point data to a continuous raster surface is demonstrated. Field data are used to assess the accuracy of the point-based aerial helicopter survey data and the kernel density estimator is extended to incorporate data uncertainty. While the accuracy of point-based aerial surveys is high, with 92.6% of points differing by no more than ± 10 trees, there is a general tendency to overestimate infestation magnitude. The method developed for incorporating uncertainty into the kernel density estimator reduces overestimation and improves the correspondence between estimated infestation intensities and field data values.