Mapping Saguaro Cacti Using Digital Aerial Imagery in Saguaro National Park
Advisorvan Leeuwen, Willem
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe saguaro cactus has been the subject of extensive ecological research since the establishment of Saguaro National Monument in 1933. Saguaro mapping and monitoring has always been limited in extent due to inherent restrictions of in situ field methods. This research developed a method for automated mapping of mature saguaros over large extents using fine spatial resolution digital aerial imagery. Saguaro shadow signatures were identified using a novel contrasting custom search kernel method. The shadows detected were used as proxies for mature saguaro locations. This research focused on (1) the development of a method of automatically identifying saguaros using their shadows in aerial imagery, (2) applying the method to aerial imagery of Saguaro National Park (SNP) to conduct a large extent saguaro census, (3) validation of the saguaro distributions against in situ field measurements, (4) investigating causes of shadow omissions, (5) estimating total saguaro densities and populations in SNP. The shadow method developed identified 446,092 saguaros across 231 square kilometers in Saguaro National Park. These results were found to be highly correlated (R2 value of 0.966) with saguaro locations recorded by SNP staff in 11 field plots in 2011. This study demonstrates that mature saguaros can be reliably mapped automatically using digital aerial imagery. The method developed will facilitate saguaro monitoring and ecological resource management in SNP and throughout the range of the saguaro cactus.
Degree ProgramGraduate College