Helicopter-based laser scanning: a method for quantitative analysis of large-scale sedimentary architecture

Abstract

Studies of large-scale sedimentary architecture are mainly based on the interpretation of two-dimensional photomosaics. This method cannot account for the natural rugosity of outcrop exposures, introducing errors in the measurement of geobody sizes and orientations. In the past, three-dimensional outcrop studies have relied on time-intensive fieldwork, with irregular sampling and low geometric accuracy. More recently, terrestrial laser scanning, or LiDAR (Light Detection and Ranging), has been widely applied to small-scale outcrops, but range and accessibility preclude its usage on larger-scale outcrops. Oblique helicopter-based laser scanning, however, allows the collection of tens of kilometres of outcrop sections in a relatively short time frame. In this paper, a procedure for collecting and processing such virtual outcrop data is outlined, and the application of the technique for extracting dimensions of fluvial geobodies from two large and otherwise inaccessible outcrops from Utah is presented. The results are compared to interpretations from more conventional photomosaicking of the same outcrops. Results show that the use of helicopter-based laser scanning enables geoscientists to rapidly acquire georeferenced data that can then be used for sedimentological interpretation and analysis on reservoir scales. It is concluded that helicopter-based laser scanning promotes sedimentological research and is well suited to capturing quantitative geometrical data from large outcrops.

The application of outcrop analogues in geological modelling: a review, present status and future outlook

“…Bellian et al 2005) but, more recently, the points are triangulated and images are draped on to the surface generating a photo-realistic model that can be used to generate highly accurate and precise measurements of geobodies in the outcrop (van Lanen et al 2009;. More recently, helicopter-mounted LiDAR has been used to collect very large datasets, km to tens of km long (Buckley et al 2008b;Rittersbacher et al 2013).…”

“…Stephen et al 2001;. A number of databases has been built to facilitate the storing and accessing of such data (Cuevas Gozalo & Martinius 1993;Reynolds 1999;Eschard et al 2002;Baas et al 2005;Gibling 2006;Colombera et al 2012;Rittersbacher et al 2013), making such data more readily available. The generation of synthetic seismic data from outcrops (e.g.…”

“…channels or bars) and/or barriers (e.g. intrashoreface shales) formed by the relative proportions of a particular set of facies (Reynolds 1999;Gibling 2006;Rittersbacher et al 2013); † relationships between directional dimensions (e.g. width v. thickness); † variograms, in cases where facies are to be modelled using a pixel-based method (e.g.…”

Point clouds from oblique stereo-imagery: Two outcrop case studies across scales and accessibility

“…Traditional air-and space borne nadir-looking sensors are appropriate for regional structures but fail to resolve the finer details because of inappropriate field of view [Dueholm, 1992;Rittersbacher et al, 2013]. This makes photogrammetry from oblique images using handheld cameras interesting because it can be deployed from a helicopter or a small aircraft at an optimal viewing angle perpendicular to the slope of the outcrop without the need to modify the aircraft.…”

“…Using photogrammetry at close range with a helicopter Digital photogrammetry may be applied at closer range from for example a helicopter, similar to the obliquely looking lidar systems developed for mapping of steep terrains [Vallet et al, 2004;Buckley et al, 2008b;Rittersbacher et al, 2013]. Although obliquely looking lidar systems have been successfully used for detailed mapping of inaccessible near-vertical cliffs, data collection with such systems is very expensive [Hodgetts, 2013].…”