Two-dimensional seismic models of geologic data are usually based on s
implified impedance functions: large ''seismic-scale'' lithologic bloc
ks exhibit uniform impedance values, and abrupt changes in impedance o
ccur at the boundaries of these lithologic blocks. For outcrop-based s
eismic models, erosional slope topography may be one possible proxy fo
r impedance that is relatively easy to measure in outcrop. In this pap
er, we use terrestrial photogrammetric techniques to establish the rel
ationship between outcrop topography, expressed as the rock slope angl
e, and impedance for a marl-limestone terrain in the Vercors, southeas
t France. The photogrammetric surveys were combined with sedimentologi
c descriptions and petrophysical measurements (including P-wave veloci
ty, bulk-density, clay content, and porosity). The slope angle along a
particular vertical profile was then converted into a pseudoimpedance
log, which was subsequently used to construct 1-D synthetic seismogra
ms. A comparison of these new seismograms with published seismic model
s of the same area revealed the benefits of the new approach, in parti
cular for seismic modeling using high-frequency source wavelets.