Collecting Inexpensive High Resolution Aerial and Stereo Images of Small- to Mid-Scale Geomorphic and Tectonic Features
Abstract
Methods for collecting accurate, mm- to cm-scale stereoscopic aerial imagery of both small- and mid-scale geomorphic features are developed for a one-time cost of under $1500. High resolution aerial images are valuable for documenting and analyzing small- to mid-scale geomorphic and tectonic features. However, collecting images of mid-scale features such as landslides, rock glaciers, fault scarps, and cinder cones is expensive and makes studies that rely on high resolution repeat imagery prohibitive for undergraduate geology departments with limited budgets. In addition to cost, collecting images of smaller scale geomorphic features such as gravel bars is often impeded by overhanging vegetation or other features in the immediate environment that make impractical the collection of aerial images using standard airborne techniques. The methods provide high resolution stereo photos suitable for image processing and stereographic analysis; the images are potentially suitable for change analyses, velocity tracking, and construction of lidar-resolution digital elevation models. We developed two techniques. The technique suitable for small-scale features (such as gravel bars) utilizes two Nikon D3000 digital single-lens reflex (DSLR) cameras attached to a system of poles that suspends the cameras at a height of 4 meters with a variable camera separation of 0.6 to 0.9 m. The poles are oriented such that they do not appear in the photographs. The cameras are simultaneously remotely activated to collect stereo pairs at a resolution of 64 pixels/cm2 (pixel length is 1.2 mm). Ground control on the images is provided by pegs placed 5 meters apart, GPS positioning, and a meter-stick included in each photograph. Initial photo data gathered of a gravel bar on the Henry’s Fork of the Snake River, north of Rexburg, Idaho is sharp and readily segmented using the MatLab-based CLASTS image processing algorithm. The technique developed for imaging mid-scale features (such as cinder cones) consists of a tethered weather balloon with a gimbal that keeps the camera oriented vertically. A single DSLR camera is suspended at an elevation of approximately 45 m. The camera is operated via a radio-controlled apparatus that enables the user to view the area being photographed prior to activating the shutter. The balloon is physically moved to capture the second image of the stereo pair. Resolution of the images is 3600 pixels/m2 (pixel length is 1.6 cm). The techniques demonstrate that collecting high-resolution stereographic aerial photographs can be accomplished on a limited budget. The techniques and equipment will be used to collect repeat images for several multi-year studies, including monitoring gravel bar evolution, vector tracking of landslide and rock glacier motion, and monitoring fault scarp and cinder cone degradation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMIN33B1307W
- Keywords:
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- 1926 INFORMATICS / Geospatial;
- 1928 INFORMATICS / GIS science