The density of ALSM data provides more than three noncollinear points on many bedding surfaces, which theoretically provides a means for calculating local surface orientation. Decimation is performed after projection because constraint points too near each other may result in numerical instabilities in the MCS interpolation [Sandwell, 1987; Wessel and Bercovici, 1998]. After GPS processing, a Kalman filter algorithm, implemented in the Applanix™ software POSProc™, was used to integrate 1 Hz differential GPS data and 200 Hz IMU recordings to produce a smoothed and blended solution for aircraft position and orientation at 200 Hz. Approximately half of the points extracted from the DEM (258,769) represent the top of the Tensleep Sandstone (mapped orange), while the fewest points (167) represent the surface in the Gypsum Springs Formation mapped in gold. Ninety‐five percent of outcrops are characterized by RMS error less than 25 m, 92% by error less than 20 m, and 83% by error less than 10 m. The maximum RMS error, however, is 1327 m, corresponding to omission of the most southeastern outcrop in the Gypsum Springs Formation, northeast of the forelimb syncline. The Bighorn Basin is a structural low, with the Absaroka Range to the west, the Bighorn Mountains to the east, and the Owl Creek Mountains to the south. However, thickness measurements show significant variability (standard deviation is typically about 10% of the mean thickness for a given stratigraphic package) and error bars are relatively large. RMS difference was 5.9 cm. One is filtered to remove vegetation and buildings, and the other is unfiltered. The upper Phosphoria Formation consists of a massive, carbonate‐rich quartz arenite [Bellahsen et al., 2006a], the top of which is mapped red. [26] Subtle but apparent thinning of the Chugwater Shale in the forelimb calls into question the parallel fold assumption, but is accounted for by reducing the projection distances through the Chugwater in the forelimb by 17 m. Projection of ALSM points in the Cloverly formation at the northwest tip of the fold present an additional challenge to the parallel fold assumption. Down‐plunge view (6° plunge at N34°W) of the fold on cross section A‐A′ (, Triangulated surfaces are generated from ALSM points representing each outcrop to calculate local surface orientation. Deformation of the rock concentrates along the fractures. Although the method has limitations, the resulting surface captures details of fold geometry that are not represented in models developed using traditional methods. Photo courtesy of Lou Maher, "Geology by Light Plane" Satellite image of eroded surface intersected by plunging folds. Several surfaces are less continuous, but were mapped because they are in a similar stratigraphic position to other mapped surfaces, and are exposed in areas where the adjacent surface does not provide good outcrops. [50] A good example of the improvement offered by the new model, although subtle, may be observed in the change of bedding strike along the fold in the backlimb northwest of the thumb structure (around point A in Figure 11b). Additionally, the Green's function approach enables the implementation of a variety of regularization (smoothing) techniques, by which it is possible to relax the requirement that the interpolated surface exactly honor all data constraints. However, uncertainty would be very great, given the 200 m thickness and homogeneous composition of the Chugwater Shale. [10] Airborne laser swath mapping (ALSM), also known as airborne lidar (light detection and ranging), utilizes a laser rangefinder mounted on a fixed‐wing aircraft or helicopter, which emits pulses and records reflection returns at a high temporal frequency while scanning laterally and compiling a dense swath of data points representing the topography of Earth's surface beneath the flight path. Geologic map of the Sheep Mountain--Little Sheep Mountain area, Big Horn County, Wyoming / U.S. Department of the Interior, U.S. Geological Survey ; by Robert L. Rioux. Subtle features of the fold between cross sections are not captured by these methods. [1996] model the strike changes relatively abruptly; however, in the new model this change is gradual. google_ad_height = 600; Shown above is a railroad cut that runs through this northwest-southeast trending anticline. Geologic map of the Sheep Mountain--Little Sheep Mountain area, Big Horn County, Wyoming / U.S. Department of the Interior, U.S. Geological Survey ; by Robert L. Rioux. [11] An ALSM survey at SMA, covering approximately 86 km2, was flown by the National Center for Airborne Laser Mapping (NCALM) in July 2007. RMS error across the model is 2.09 m, and 95% of outcrops are characterized by RMS error less than 5 m. Maximum RMS error for any outcrop due to smoothing of the interpolated surface is 40 m. Average misfit magnitudes are several times greater where training points are omitted in cross validation than the misfit magnitudes inherent to the smoothed interpolation. Shown above is a railroad cut that runs through this northwest-southeast. Aerial view of the Sheep Mountain Anticline in Wyoming, USA. (b) Thickness versus local dip. This contradicts the parallel folding hypothesis, and is accounted for as described in section 5.1. Cross section B‐B′ displays the greatest deviation from parallel folding, which persists from the hinge, northwest through the forelimb and forelimb syncline. [2009] address this issue at Raplee Ridge by simultaneously interpolating multiple surfaces while applying inequality constraints to intervening layer thicknesses to maintain a physically realistic model without surface interpenetration or excessive thinning or thickening. Even if the specific data points used by Forster et al. comment type: geology: comment: geol.desc: placer-fossil-beach and marine: comment type: geology: comment: The sandstone at the base of the Frontier Formation is the youngest ridge‐forming unit exposed in the extent of the ALSM survey. It is the surface expression of an upward fold in the earth’s crust that geologists refer to as an anticline. An About 30 such points were identified and discarded from the constraint set. The highway was nicknamed “Sweet 16” because it presents the modern traveler with a scenic and safe route across this 90 mile long and 30 mile wide mountain range. Small horizontal errors are prevalent among the projected data in this region, particularly for data points projected more than 200 m across the Chugwater Shale, because a large component of the projection vector for steeply dipping surfaces is in the horizontal plane. The Bighorn River cuts the anticline normal to the fold