Improving quantitative ventifact analysis for climate investigations using the Dyngjusandur sandsheet in Iceland as a planetary analogue

Abstract

We use the Dyngjusandur sandsheet, Iceland, as a testbed to assess the type and number of measurements required to accurately represent ventifact orientations and extract palaeowind information through a statistical evaluation of the differences between photogrammetric based and in situ measurements of ventifact feature orientations. Forty representative ventifacts were selected for in situ measurement, 20 of which were imaged for photogrammetric analysis to produce oriented and scaled virtual 3D models. An additional set of measurements were made on the ‘synthetic’ models to allow for statistical assessment of erosional feature orientation. Despite the similarity between the photogrammetric (1145 measurements) and the in situ datasets (500 measurements), there are small but significant differences in mean feature orientation that become more pronounced as sample size is reduced. Results indicate that in situ and photogrammetric methods of measuring feature orientation are comparable (to within 2° ± 2° at 1 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> mml:miσ</mml:mi> </mml:math> ( n = 20) for inferring palaeowind directions), but photogrammetric analyses require less time for data acquisition (by a factor of 0.36–0.66) and yield over five times (5.16 times) as many measurements per ventifact, with additional advantages of being able to examine digital objects under different illumination conditions and magnifications, and from angles that are otherwise not possible in the field.