  Conventional fracture data collection methods are usually implemented on
planar surfaces or assuming they are planar; these methods may introduce
sampling errors on uneven outcrop surfaces. Consequently, data collected on
limited types of outcrop surfaces (mainly bedding surfaces) may not be a
sufficient representation of fracture network characteristic in outcrops.
Recent development of techniques that obtain DOMs from outcrops and extract the
full extent of individual fractures offers the opportunity to address the
problem of performing the conventional sampling methods on uneven outcrop
surfaces. In this study, we propose a new method that performs outcrop fracture
characterization on suppositional planes cutting through DOMs. The
suppositional plane is the best fit plane of the outcrop surface, and the
fracture trace map is extracted on the suppositional plane so that the fracture
network can be further characterized. The amount of sampling errors introduced
by the conventional methods and avoided by the new method on 16 uneven outcrop
surfaces with different roughnesses are estimated. The results show that the
conventional sampling methods don't apply to outcrops other than bedding
surfaces or outcrops whose roughness > 0.04 m, and that the proposed method can
greatly extend the types of outcrop surfaces for outcrop fracture
characterization with the suppositional plane cutting through DOMs.
