Digital Mobile Sketch Mapping Forest Mortality from 2016 to 2023 on East Hawai'i Island

Digital Mobile Sketch Mapping (DMSM) is a USDA Forest Service custom app with tablet hardware, software, and back end data support processes (ArcGIS Desktop Tools) that allow trained aerial surveyors, in light aircraft, and ground observers to record forest disturbances and their causal agents. Helicopter-based state-wide forest health surveys for ROD using Digital Mobile Sketch Mapping (DMSM) began in 2016 and are semiannually conducted by the Hawai‘i Island Department of Land and Natural Resources, Division of Forestry and Wildlife (DLNR DOFAW) and Big Island Invasive Species Committee (BIISC) as part of the annual Forest Health Monitoring (FHM) Program of the Forest Service, US Department of Agriculture. The DMSM survey protocol for Hawai‘i Island includes mapping fresh mortality (brown and red crowns) up to 1.6 km out from the helicopter track, though this can extend to 3.2 km with clear visibility and a surveyor’s knowledge of landmarks and geographic identifiers. Helicopter flightline track buffers were generated from recorded DMSM flight track data at widths of 1.6 km, 2.4 km, and 3.2 km to calculate flight coverage area. The maximum buffer distance was set to 3.2 km since accurate mortality identification beyond this distance is uncertain. The most conservative area extent was chosen for DMSM coverage area using the best fit buffer that encompassed the majority of mapped mortality each year. Mortality points were buffered based on tree quantity and converted to polygons as part of the post-processing procedure to calculate total mortality area. Annual DMSM forest mortality polygons containing any level of recorded mortality, ranging from very light (1- 3%) to very severe (>50%) were included with no filtering and used to generate a time series of mapped mortality area from 2016 to 2023 within East Hawai'i. Datasets are in WGS-84, UTM Zone 5N (EPSG: 32605).