Deriving shrub heights from high resolution stereo-pair aerial imagery: An application for broad-scale rangeland monitoring

TitleDeriving shrub heights from high resolution stereo-pair aerial imagery: An application for broad-scale rangeland monitoring
Publication TypeConference Proceedings
Year of Publication2011
AuthorsGillan JK, Karl JW, Duniway M.C.
Conference Name65th Annual Meeting of the Society for Range Management
Volumep. 0114
Date Published01/2012
PublisherSociety for Range Management
Conference LocationSpokane, Washington
ARIS Log Number286814
Abstract

Vertical vegetation structure in rangeland ecosystems can be a valuable indicator for monitoring rangeland health or progress toward management objectives because of its importance for assessing riparian areas, post-fire recovery, wind erosion, and wildlife habitat. Federal land management agencies are directed to monitor and manage rangelands at landscapes scales, but traditional field methods for measuring vegetation heights are often too costly and time consuming to apply at these broad scales. Emerging remote sensing techniques (e.g., LiDAR or synthetic aperture radar) are too expensive, require specialized sensors, or are not of high enough resolution for broad-scale application. An alternative remote sensing approach is to measure vegetation heights from digital stereo aerial photographs. The purpose of this study was to test the feasibility and accuracy of estimating shrub heights from highresolution (HR, 3-cm ground sampling distance) digital stereo-pair aerial images. Overlapping HR imagery was taken in March 2009 near Lake Mead National Recreation Area and 5 cm resolution digital terrain models (DTMs) were created for five 2,500 m2 test plots. Average shrub heights from the DTMs were compared to field measurements from the test plots, yielding results suggesting this technique has potential for estimating shrub heights. However, compared to typical field methods, average shrub heights from the DTMs were consistently underestimated because the resolution of the imagery was not able to capture fine branches measured in the field. Through the use of statistically derived correction factors, though, vegetation heights from HR DTMs could be a valuable technique for broad-scale rangeland monitoring needs.