Multi‐scale relief model (MSRM): a new algorithm for the visualization of subtle topographic change of variable size in digital elevation models

Abstract

Morphological analysis of landforms has traditionally relied on the interpretation of imagery. Although imagery provides a natural view of an area of interest (AOI) images are largely hindered by the environmental conditions at the time of image acquisition, the quality of the image and, mainly, the lack of topographical information, which is an essential factor for a correct understanding of the AOI's geomorphology.More recently digital surface models (DSMs) have been incorporated into the analytical toolbox of geomorphologists. These are usually high-resolution models derived from digital photogrammetric processes or LiDAR data. However, these are restricted to relatively small areas and are expensive or complex to acquire, which limits widespread implementation.In this paper, we present the multi-scale relief model (MSRM), which is a new algorithm for the visual interpretation of landforms using DSMs. The significance of this new method lies in its capacity to extract landform morphology from both high-and low-resolution DSMs independently of the shape or scale of the landform under study. This method thus provides important advantages compared to previous approaches as it: (1) allows the use of worldwide medium resolution models, such as SRTM, ASTER GDEM, ALOS, and TanDEM-X; (2) offers an alternative to traditional photograph interpretation that does not rely on the quality of the imagery employed nor on the environmental conditions and time of its acquisition; and (3) can be easily implemented for large areas using traditional GIS/RS software.The algorithm is tested in the Sutlej-Yamuna interfluve, which is a very large low-relief alluvial plain in northwest India where 10 000 km of palaeoriver channels have been mapped using MSRM. The code, written in Google Earth Engine's implementation of JavaScript, is provided as Supporting Information for its use in any other AOI without particular technical knowledge or access to topographical data.

Mapping Archaeology While Mapping an Empire: Using Historical Maps to Reconstruct Ancient Settlement Landscapes in Modern India and Pakistan

“…It is important to acknowledge that the methods outlined here for making use of these Survey of India 1" to 1-mile maps are only likely to be useful for identifying mounded sites, and will not be suitable to aid detection of a wide range of other features of archaeological significance. Therefore, it is essential to integrate the use of these historical maps into comprehensive approaches that make use of the full suite of earth observation and remote sensing techniques, potentially integrating open-source multi-spectral data and the computational power of platforms like Google Earth Engine to identify hydrological and topographic features not easily visible on the surface [35,90,91]. It is also imperative that these remote prospection approaches are co-ordinated with large-scale ground-truthing surveys, that will verify which of the mound features are archaeological sites, and establish a reliable chronology for those sites and the associated landscapes.…”

Why Not a Single Image? Combining Visualizations to Facilitate Fieldwork and On-Screen Mapping

“…Some techniques are simple to compute, e.g., analytical hillshading and slope gradient, while others are more complex, e.g., sky-view factor [13], local relief model [19], red relief image map [20], multidirectional visibility index [21], or multiscale integral invariants [22]. While the first set of techniques focus on small-scale topographical forms, the latter consider topographic change of varying size and express it in a single image, similar to multiscale relief model [23]. An interesting approach uses a combination of a normalized digital surface model (nDSM) or a canopy height model (CHM) and shaded relief or a grayscale orthophoto image that help evaluate the immediate environment of archaeological features, especially when covered by forest.…”

COSMO-SkyMed SAR for Detection and Monitoring of Archaeological and Cultural Heritage Sites

“…First studies using this product (available now for 97% of global landmass) for geomorphological applications and landscape archaeology are now appearing in the literature (e.g., [41]). Additionally, there are some studies (albeit still few) presenting the results achieved with DEMs purposely generated for archaeological applications using higher resolution SAR images.…”