Karsten Lambers

Neolithic to Bronze Age (4850–3450 cal. BP) fire management of the Alpine Lower Engadine landscape (Switzerland) to establish pastures and cereal fields

Agro-pastoral activities in the past act as environmental legacy and have shaped the current cultural landscape in the European Alps. This study reports about prehistoric fire incidents and their impact on the flora and vegetation near the village of Ardez in the Lower Engadine Valley (Switzerland) since the Late Neolithic Period. Pollen, charcoal particles and non-pollen palynomorphs preserved in the Saglias and Cutüra peat bog stratigraphies were quantified and the results compared with the regional archaeological evidence. Anthropogenic deforestation using fire started around 4850 cal. BP at Saglias and aimed at establishing first cultivated crop fields (e.g. cereals) and small pastoral areas as implied by the positive correlation coefficients between charcoal particles and cultural and pastoral pollen indicators, as well as spores of coprophilous fungi. Pressure on the natural environment by humans and livestock continued until 3650 cal. BP and was followed by reforestation processes until 3400 cal. BP because of climatic deterioration. Thereafter, a new, continuous cultivation/pastoral phase was recorded for the Middle to Late Bronze Age (3400–2800 cal. BP). After rather minor human impact during the Iron Age and Roman Period, intensive agriculture was recorded for the Medieval Period. The area around Ardez was used for crop cultivation from about 1000 cal. BP until the start of the ‘Little Ice Age’ (600 cal. BP). Despite a land-use reorganisation, the following gradual decrease in agricultural activities led to the extant mixture of a cultivated, grazed and forested landscape in the Lower Engadine. In addition, this study demonstrates the excellent value of the fungus Gelasinospora as a highly local marker of past and today’s fire incidents, as well as of the use of micro-charcoals from pollen slides and macro-charcoals (>150 µm) from pollen sample residues for the reconstruction of short- and long-term fire histories.

Morphological operators for segmentation of high contrast textured regions in remotely sensed imagery

We develop a transformation based on morphological filters that measures the contrast of image texture. This transformation is proportional to texture contrast, but insensitive to its specific type. Though the transformation provides a high response in textured areas, it suppresses individual high contrast features that stand apart from textured areas. It can serve as an effective texture descriptor for unsupervised or supervised segmentation of textured regions, provides high accuracy of localization and does not involve heavy computations. The method is robust to variations of illumination and works on different types of images without needing to be tuned. The only parameter is a scale related parameter. We illustrate the use of the proposed method on satellite and aerial images.

A morphological approach for distinguishing texture and individual features in images

We present a morphological texture contrast (MTC) operator that allows detection of textural and non-texture regions in images. We show that in contrast to other approaches, the MTC discriminates between texture details and isolated features and does not extend borders of texture regions. A comparison with other methods used for texture detection is provided. Using the ideas underlying the MTC operator, we develop a complementary operator called morphological feature contrast (MFC) that allows extraction of isolated features while not being confused by texture details. We illustrate an application of the MFC operator to extraction of isolated objects such as individual trees or buildings that should be distinguished from forests or urban centers. We also propose an MFC based detector of isolated linear features and compare it with an alternative approach used for detection of edges and lines in cluttered scenes. We furthermore derive an extended version of the MFC that can be directly applied to vector-valued images.

Detection of Texture and Isolated Features Using Alternating Morphological Filters

Recently, we introduced a morphological texture contrast (MTC) operator that allows detection of textural and non-texture regions in images. In this paper we provide comparison of the MTC with other available techniques. We show that, in contrast to other approaches, the MTC discriminates between texture details and isolated features, and does not extend borders of texture regions. Using the ideas underlying the MTC operator, we develop a complementary operator called morphological feature contrast (MFC) that allows extraction of isolated features while not being confused by texture details. We illustrate an application of the MFC operator for extraction of isolated objects such as individual trees or buildings that should be distinguished from forests or urban centers. We furthermore provide an example of how this operator can be used for detection of isolated linear structures. We also derive an extended version of the MFC that works with vector-valued images.

Detection of Fragmented Rectangular Enclosures in Very High Resolution Remote Sensing Images

We develop an approach for the detection of ruins of livestock enclosures (LEs) in alpine areas captured by high-resolution remotely sensed images. These structures are usually of approximately rectangular shape and appear in images as faint fragmented contours in complex background. We address this problem by introducing a rectangularity feature that quantifies the degree of alignment of an optimal subset of extracted linear segments with a contour of rectangular shape. The rectangularity feature has high values not only for perfectly regular enclosures but also for ruined ones with distorted angles, fragmented walls, or even a completely missing wall. Furthermore, it has a zero value for spurious structures with less than three sides of a perceivable rectangle. We show how the detection performance can be improved by learning a linear combination of the rectangularity and size features from just a few available representative examples and a large number of negatives. Our approach allowed detection of enclosures in the Silvretta Alps that were previously unknown. A comparative performance analysis is provided. Among other features, our comparison includes the state-of-the-art features that were generated by pretrained deep convolutional neural networks (CNNs). The deep CNN features, although learned from a very different type of images, provided the basic ability to capture the visual concept of the LEs. However, our handcrafted rectangularity-size features showed considerably higher performance.

Automated search for livestock enclosures of rectangular shape in remotely sensed imagery

We introduce an approach for the detection of approximately rectangular structures in gray scale images. Our research is motivated by the Silvretta Historica project that aims at automated detection of remains of livestock enclosures in remotely sensed images of alpine regions. The approach allows detection of enclosures with linear sides of various sizes and proportions. It is robust to incomplete or fragmented rectangles and tolerates deviations from a perfect rectangular shape. Morphological operators are used to extract linear features. They are grouped into parameterized linear segments by means of a local Hough transform. To identify appropriate configurations of linear segments we define convexity and angle constraints. Configurations meeting these constraints are rated by a proposed rectangularity measure that discards overly fragmented configurations and configurations with more than one side completely missing. The search for appropriate configurations is efficiently performed on a graph. Its nodes represent linear segments and edges encode the above constraints. We tested our approach on a set of aerial and GeoEye-1 satellite images of 0.5m resolution that contain ruined livestock enclosures of approximately rectangular shape. The approach showed encouraging results in finding configurations of linear segments originating from the objects of our interest.

Context matters : GIS-based spatial analysis of the Nasca geoglyphs of Palpa

In this chapter we report on the GIS-based analysis of the Nasca geoglyphs of Palpa, Peru, undertaken in the course of the Nasca–Palpa Archaeological Project. We focus here on the analysis of spatial relationships between the geoglyphs and the surrounding landscape in terms of visibility and orientation. Our motivation for this contextual analysis was to gain a better understanding of the function and meaning of the geoglyphs by virtually assuming the viewpoints of the people who conceived, built, and used the geoglyphs between approximately 400 BC and 800 AD. In this sense our study of geoglyph visibility and orientation is a contribution to current attempts to incorporate cultural variables into the quantitative environment of GIS, thereby rendering GIS a more useful instrument for archaeological research. This approach required the development of new GIS tools tailored to the specific needs of archaeological analysis. The results of our study indicate that the geoglyphs can be understood as stages for public rites performed by social groups, whereas the incorporation of the surrounding landscape through visual links was apparently not a major concern.

Detection of incomplete enclosures of rectangular shape in remotely sensed images

We develop an approach for detection of ruins of livestock enclosures in alpine areas captured by high-resolution remotely sensed images. These structures are usually of approximately rectangular shape and appear in images as faint fragmented contours in complex background. We address this problem by introducing a new rectangularity feature that quantifies the degree of alignment of an optimal subset of extracted linear segments with a contour of rectangular shape. The rectangularity feature has high values not only for perfect enclosures, but also for broken ones with distorted angles, fragmented walls, or even a completely missing wall. However, it has zero value for spurious structures with less than three sides of a perceivable rectangle. Performance analysis using large imagery of an alpine environment is provided. We show how the detection performance can be improved by learning from only a few representative examples and a large number of negatives.

Airborne and Spaceborne Remote Sensing and Digital Image Analysis in Archaeology

Remote sensing has a long and successful track record of detecting and mapping archaeological traces of human activity in the landscape. Since the early twentieth century, the tools and procedures of aerial archaeology evolved gradually, while earth observation remote sensing experienced major steps of technological and methodological advancements and innovation that today enable the monitoring of the earth’s surface at unprecedented accuracy, resolution and complexity. Much of the remote sensing data acquired in this process potentially holds important information about the location and context of archaeological sites and objects. Archaeology has started to make use of this tremendous potential by developing new approaches for the detection and mapping of archaeological traces based on digital remote sensing data and the associated tools and procedures. This chapter reviews the history, tools, methods, procedures and products of archaeological remote sensing and digital image analysis, emphasising recent trends towards convergence of aerial archaeology and earth observation remote sensing.