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ALS-derived raster visualization techniques have become common in recent years, opening up new possibilities for subtle landform detection in earth sciences and archaeology, but they have also introduced confusion for users. As a consequence, the choice between these visualization techniques is still mostly supported by empirical knowledge. Some attempts have been made to compare these techniques, but there is still a lack of analytical data. This work proposes a new method, based on gradient modelling and spatial statistics, to analytically assess the efficacy of these visualization techniques. A selected panel of outstanding visualization techniques was assessed first by a classic non-analytical approach, and secondly by the proposed new analytical approach. The comparison of results showed that the latter provided more detailed and objective data, not always consistent with previous empirical knowledge. These data allowed us to characterize with precision the terrain for which each visualization technique performs best. A combination of visualization techniques based on DEM manipulation (Slope and Local Relief Model) appeared to be the best choice for normal terrain morphometry, occasionally supported by illumination techniques such as Sky-View Factor or Negative Openness as a function of terrain characteristics. [ABSTRACT FROM AUTHOR]

Fifteen years ago, the introduction of mobile multipole arrays led to substantial improvements in shallow electric prospection because it allowed information related to the vertical distribution of ground resistivity, in complement to the horizontal pattern of the detected features, to be extracted. However, to make full use of this wealth of information, further progress is needed to extend the qualitative interpretation of data to a more quantitative evaluation of the explored terrain. To that intent, we developed a two-step process: In the first step, a 1D electric model is fitted to the data over the full explored area, and in the second step, using the moment method, localized 3D interpretation is applied to limited areas, for which the characteristics of a given feature require closer scrutiny. After a first test with synthetic data generated using the surface integral 3D modeling method, this process was applied to three different archaeological sites and one test site, for both handheld pole-pole array systems and a multipole continuous electric profiling mechanically pulled system. At the test site, the characteristics of a known wall were accurately recovered. At the Duntzenheim site, the thickness and width of the archaeological remains determined by 3D interpretation corresponded to the features observed through excavation. At the other two sites, 3D interpretation made it possible to establish that the conductive features extend across the full extent of the superficial resistive second layers. [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic induction (EMI) is one of the geophysical techniques widely used in soil studies, the slingram devices being held horizontally over the soil surface, i.e. with the coils located at the same height above the ground surface. Our study aims assessing the abilities of slingram devices when held vertically. 1D and 3D modelling have been achieved in order to compare the theoretical responses of vertical devices to the horizontal ones. Some comparative surveys were also undertaken in archaeological contexts to confirm the reliability of theoretical conclusions. Both approaches show that vertical slingram devices are suitable for survey and can constitute an alternative to the usual horizontal orientation. We give a table in Appendix A which contains the calibration coefficient allowing transforming of the values given by some of commercially available devices which would be advantageous to use in vertical orientation [Copyright &y& Elsevier]