Abstract. We have generated sub-millimetre-resolution DEMs of weathered rock surfaces
using SfM photogrammetry techniques. We apply a close-range method based on structure-from-motion (SfM)
photogrammetry in the field and use it to generate
high-resolution topographic data for weathered boulders and bedrock. The
method was pilot tested on extensively weathered Triassic Moenkopi sandstone
outcrops near Meteor Crater in Arizona. Images were taken in the field using
a consumer-grade DSLR camera and were processed in commercially available
software to build dense point clouds. The point clouds were registered to a
local 3-D coordinate system (x, y, z), which was developed using a specially
designed triangle-coded control target and then exported as digital elevation
models (DEMs). The accuracy of the DEMs was validated under controlled
experimental conditions. A number of checkpoints were used to calculate
errors. We also evaluated the effects of image and camera parameters on the
accuracy of our DEMs. We report a horizontal error of 0.5 mm and vertical
error of 0.3 mm in our experiments. Our approach provides a low-cost method
for obtaining very high-resolution topographic data on weathered rock
surfaces (area < 10 m2). The results from our case study confirm
the efficacy of the method at this scale and show that the data acquisition
equipment is sufficiently robust and portable. This is particularly important
for field conditions in remote locations or steep terrain where portable and
efficient methods are required.
A Structure-from-Motion Pipeline for Generating Digital Elevation Models for Surface-Runoff Analysis
