Showing items related by title, author, creator and subject.

• 

  Mapping saguaro cacti using digital aerial imagery in Saguaro National Park

  Carter, Forest; van Leeuwen, Willem J. D.; Univ Arizona, Sch Geog & Dev; Univ Arizona, Sch Nat Resources & Environm (SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2018-09-10)

  Population research on the saguaro cactus (Carnegiea gigantea) has historically been limited to repeat monitoring efforts in small plots with areas of 1 to 4 hectares. Large extent saguaro censuses of areas >2.59 km(2) have not been undertaken. This research developed an automated shadow detection method for mapping mature saguaros in digital aerial imagery using saguaro shadows as proxies for saguaro locations. The shadow method detected 446,092 saguaro shadows in aerial imagery of 231 km(2) of the Saguaro National Park (SNP) near Tucson, Arizona. The results were validated against saguaro location data in 11 small plots provided by SNP staff. The shadow method correctly identified 58% of mature saguaros in these 11 plots. Twenty-one percent of the saguaros in the plots did not produce a shadow signature in the imagery. Fieldwork was conducted in two plot locations to investigate reasons why these mature saguaros failed to produce shadow signatures in the aerial imagery, which showed that vegetation interference, rocky slopes, and shadow alignments were the primary factors that precluded shadow signatures from appearing in the imagery. This research provides a methodology for automated large-area saguaro mapping, which will be useful in long-term population monitoring and saguaro ecology research. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
• 

  Mapping Saguaro Cacti Using Digital Aerial Imagery in Saguaro National Park

  van Leeuwen, Willem; Carter, Forest; Barron-Gafford, Greg; Guertin, Philip (The University of Arizona., 2018)

  The 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.
• 

  Traditional Saguaro Harvest in the Tucson Mountain District, Saguaro National Park

  Toupal, Rebecca; Stoffle, Richard W.; Dobyns, Henry; Bureau of Applied Research in Anthropology, University of Arizona (Bureau of Applied Research in Anthropology, University of Arizona, 2006-12-15)