Efficiency and Detection Accuracy Using Print and Digital Stereo Aerial Photography for Remotely Mapping Vernal Pools in New England Landscapes

Abstract

Aerial imagery has been used to identify potential vernal pools (PVPs) using stereo photographic prints. Stereoplotter photogrammetry now allows digital aerial images to be viewed in stereo (3-Dimensional) to enhance remote sensing capabilities. We used both print and digital imagery to map PVPs in 10 towns in Maine, USA. We used field verification of 771 PVPs to explore efficiency and accuracy of the two methodologies and to determine effects of pool size and land cover on accuracy. We compared known pool locations with National Wetland Inventory (NWI) data. The stereoplotter was more efficient and easier to use than prints. In the towns where print imagery was used, 77.4 % of surveyed PVPs were confirmed as compared to 60.8 % of PVPs surveyed in the towns with digital photography. The higher commission errors using the digital method were likely due to enhanced ability to detect smaller features. Omission errors were common using both print and digital methods. Only 43 % of confirmed vernal pools were located in areas mapped by NWI, suggesting that NWI information does not improve detection accuracy. Aerial photo interpretation continues to be effective for PVP identification in our region and is improved with the use of digital stereoplotters.