Digital image analysis of outcropping sediments

The possibility to use colour data, a fast and inexpensive method of proxy data generation, extracted from two selected loess-paleosol sequences is discussed here. We compare the outcome from analysing outcrop images taking by digital cameras in the field and spectral colour data as determined under controlled laboratory conditions. By nature, differences can be expected due to differences in illumination, moisture, and sample preparation. Outcrop inclination may be an issue for photographs; correcting for this is possible when marks can be used for rectification. In both cases the data extracted from images match the visual impression of photos well, and are useful for obtaining a more quantitative measure for field observations. Smoothness (as measured by autocorrelation) is high for an image from Achenheim/France, where an image with a width of ca. 1.1 m and a depth of 1.6 m was analysed. Data from a narrower image part from Sanovita/Romania are noisier. In both example cases, a significant correlation between data extracted by digital image analysis and laboratory measurements could be established, suggesting that image analysis may be a useful tool where outcrop- and light-conditions allow useful photographs, especially where high resolution proxy data is required.