Cartografía semi-automática de terrazas de cultivo a partir de datos LiDAR

The mountain systems surrounding the Mediterranean suffered a huge transformation related with the agriculture, mainly as a consequence of the agricultural terraces construction. These structures modify the topography and soils distribution, and, as a consequence, the drainage basins hydro-erosive dynamics. The massive land abandonment especially during the second half of the 20th century conduced to an afforestation associated with the occurrence of wild fires. The combination of fires and the collapse of the terraces walls has accelerated soil erosion processes. Actual sources of topographical data –mainly the airborne LiDAR- and the image analysis tools, offers an adequate resolution to get the land surface elements patters and map landforms such terrace steps. This paper explores the possibilities of such data sources and tools and pretends mapping the terrace walls both active and abandoned for the agricultural practices. Two small catchments have been selected in Mallorca and Castelló as samples characterised by the massive presence of agricultural terraces and using airborne LiDAR data has applied a procedure that produced satisfactory results. The maps have been check by means of photointerpretation and field work, and an exploratory work has been done analysing the influence of the terraces over the erosion processes by means of the study of the structural connectivity applying to the DTMs a Connectivity Index (IC)

Determinación cartográfica de los muros de piedra seca de la Sierra de Tramuntana mallorquina (Islas Baleares): Análisis exploratorio

The «art of dry-stone walling», declared as Intangible Cultural Heritage by UNESCO, has historically materialized, in Mallorca, with a varied list of constructions with different functions. The massive habilitation of dry stone walls in the Mallorcan rural area has left an outstanding landscape and territorial footprint, which constitutes a rich source of geographical analysis. We present, as an essay, an unpublished cartography of the dry-stone walls located in the Sierra de Tramuntana (Majorca), cartography that has served as the basis for its classification and provisional quantification. With the support of basic techniques of cartography, photointerpretation and GIS, the detailed examination of two official cartographic bases has allowed to determine their usefulness as reliable sources of location and knowledge of dry stone walls in our study area, with a view to a longer range geographical analysis.La técnica constructiva de la piedra seca, declarada Patrimonio cultural inmaterial de la Humanidad por la UNESCO, se ha materializado históricamente, en Mallorca, en forma de un variado elenco de construcciones con diferentes funciones. La masiva habilitación de muros de piedra seca en el espacio rural mallorquín ha dejado una sobresaliente huella paisajística y territorial, que constituye una rica fuente de análisis geográfico. Se presenta, a modo de ensayo, una cartografía inédita de los muros localizados en la Sierra de Tramuntana mallorquina, cartografía que ha servido de base para su clasificación y cuantificación provisional. Con el apoyo de técnicas básicas de cartografía, fotointerpretación y SIG, el examen pormenorizado de dos bases cartográficas oficiales ha permitido dirimir su utilidad como fuentes fidedignas de localización y conocimiento de los muros de piedra seca en nuestro ámbito de estudio, con vistas a un estudio geográfico de los mismos de más largo alcance

Physical geomorphometry for elementary land surface segmentation and digital geomorphological mapping

By interpretations related to energy, elementary land surface segmentation can be treated as a physical problem. Many pieces of such a view found in the literature can be combined into a synthetic comprehensive physical approach. The segmentation has to be preceded by defining the character and size of searched units to result from the segmentation. A high-resolution digital elevation model (DEM) is the key input for this task; it should be generalized to the resolution best expressing information about the searched units. Elementary land surface units can be characterized by various parts of potential gravitational energy associated with a set of basic geomorphometric variables. Elevation above sea level (z) represents Global Geomorphic Energy (GGE). Regional and Local Geomorphic Energy (RGE and LGE) are parts of GGE, represented respectively by relative elevation above the local base level (zrel) and local relief (elevation differential in a moving window Δz). Derivation (change) of elevation defines the slope inclination (S), determining the local Potential Energy of Surface (PES) applicable to mass flow. Normal slope line (profile) curvature (kn)s and normal contour (tangential) curvature (kn)c express change in the PES value (ΔPES(kn )s, ΔPES(kn )c), responsible for acceleration/deceleration and convergence/ divergence of flow. Mean curvature (kmean) determines the Potential Energy of Surface applicable to Diffusion (PESD). Energetic interpretation of basic geomorphometric variables enables their direct comparison and systematic evaluation. Consequently, the homogeneity of basic geomorphometric variables defines a hierarchy of states of local geomorphic equilibria: static equilibrium, steady state, and non-steady state dynamic equilibrium. They are local attractors of landform development reflected in the geomorphometric tendency to symmetry (horizontality, various types of linearity, and curvature isotropy, together expressed by gravity concordance). Nonequilibrium and transitional states can be characterized by the PES excess (PESe) determined by difference curvature (kd), by gravity discordant change of the PES characterized by twisting curvature (τg)c, and by Integral Potential Energy of Surface Curvature (IPESC) expressed by Casorati curvature (kC) (general curvedness). Excluding zrel and Δz, all these energy-related geomorphometric variables are local point-based. Local area-based and regional variables such as Glock’s Available Relief, Melton Ruggedness Number, Stream Power Index, Openness, Topographic Position Index, Topographic Wetness Index, and Index of Connectivity also have energetic interpretations although their definition is more complex. Therefore we suggest exclusive use of the local point-based variables in designs of elementary land surface segmentation. The segmentation should take notice of natural interconnections, the hierarchy of geomorphometric variables, elements of Local Geomorphic Energy, and (dis)equilibria states, so that elementary segments are clearly interpretable geomorphologically. This is exemplified by Geographic Object-Based Image Analysis (GEOBIA) segmentation of Sandberg, a territory on the boundary of the Carpathians and Vienna Basin with a complex geomorphic history and marked morphodynamics. Compared with expert-driven field geomorphological mapping, the automatic physically-based segmentation resulted in a more specific delineation and composition of landforms. Physical-geomorphometric characteristics of the elementary forms enabled the formulation of their system and subsequent improvement of the expert-based qualitative genetic analysis, with interpretation leading to a deeper understanding of the development and recent dynamics of the landscape

Comparison of Pleiades and LiDAR Digital Elevation Models for Terraces Detection in Farmlands

Among the most evident anthropogenic modifications of the landscape, terraces related to agricultural activities are ubiquitous structures that constitute important investments worldwide, and they recently acquired a new relevance to modern concerns about land-use management and erosion control. Conservation agriculture and terraces management are an application with great potentialities for Satellite Earth observation and the derived high-resolution topography. Due to its high agility, the Pleiades satellite constellation provides new, high-resolution digital elevation models (DEMs) with a submetric resolution that could be potentially useful for this task, and their application in a farmland context is nowadays an open research line. This work provides a first analysis, performing an automatic terrace mapping from DEMs obtained from Pleiades images, as compared to LiDAR DEMs. Two existing methods are considered: 1) the fast line segment detector (LSD) algorithm and 2) a geomorphometric method based on surface curvature. Despite the lower performances of Pleiades DEMs with respect to that of the LiDAR models, the results indicate that the Pleiades models can be used to automatically detect terrace slopes greater than 2 m with a detection rate of more than 80% of the total length of the terraces. In addition, the results showed that when using noisy DEMs, the geomorphometric method is more robust, and it slightly outperforms the LSD algorithm. These results provide a first analysis on how effective Pleiades DEMs can be as an alternative to LiDAR DEMs, also highlighting the future challenges for monitoring large extents in a farmland context

Remote Sensing and Geosciences for Archaeology

This book collects more than 20 papers, written by renowned experts and scientists from across the globe, that showcase the state-of-the-art and forefront research in archaeological remote sensing and the use of geoscientific techniques to investigate archaeological records and cultural heritage. Very high resolution satellite images from optical and radar space-borne sensors, airborne multi-spectral images, ground penetrating radar, terrestrial laser scanning, 3D modelling, Geographyc Information Systems (GIS) are among the techniques used in the archaeological studies published in this book. The reader can learn how to use these instruments and sensors, also in combination, to investigate cultural landscapes, discover new sites, reconstruct paleo-landscapes, augment the knowledge of monuments, and assess the condition of heritage at risk. Case studies scattered across Europe, Asia and America are presented: from the World UNESCO World Heritage Site of Lines and Geoglyphs of Nasca and Palpa to heritage under threat in the Middle East and North Africa, from coastal heritage in the intertidal flats of the German North Sea to Early and Neolithic settlements in Thessaly. Beginners will learn robust research methodologies and take inspiration; mature scholars will for sure derive inputs for new research and applications