(PDF) Visualising geomorphological traces of conflict in high-resolution elevation models | Ralf Hesse - Academia.edu
Visualising geomorphological traces of conflict in high-resolution elevation models Ralf Hesse, State Office for Cultural Heritage Baden-Württemberg STATE OFFICE FOR CULTURAL HERITAGE Conflict archaeology, remote sensing and geomorphology Of all search results containing „conflict archaeology“... • 47.7 % also contained „battlefield“ • 6.4 % also contained „remote sensing“ • 3.9 % also contained „geomorphology“ • 2.0 % also contained „remote sensing“ AND „geomorphology“ DEM visualisation techniques - why? • What is a DEM? DEM visualisation techniques - why? • What is a DEM? a (gridded) data set containing elevation values has to be converted into a human-readable image Shaded Relief • directional illumination from a point light source • specified azimuth and elevation (Imhof, 2007) Shaded Relief • directional illumination from a point light source • specified azimuth and elevation (Imhof, 2007) Exaggerated Relief • Rusinkiewicz et al., 2006 • based on simple Shaded Relief, but • multi-scale approach • locally adapted illumination elevation • combined by weighted mean Exaggerated Relief • pro: • single illumination direction • no overly dark or bright areas • contra: • loss of landscape forms • apparent ridges Trend Removal • subtraction of a smoothed (low-pass-filtered) version from the original DEM • pro: • highlights small topographic differences • contra: • loss of landscape forms • apparent banks and ditches Local Relief Model (LRM) • advanced trend removal method 1.6 Extraction 440 Interpolation 0m 440 Difference map 8.7 0m -3.7 0 175 m 70 m 0 175 m 0m 0 175 m -8.6 0 175 m Local Relief Model (LRM) • pro: • highlight small topographic differences • contra: • complexity, computation time • loss of landscape shapes • apparent banks and ditches Sky-View Factor (SVF) • diffuse illumination from a homogeneously bright hemisphere (Zakšek et al., 2011) (Zakšek et al. 2011, Fig. 6) Sky-View Factor (SVF) • pro: • intuitively readable • single illumination • negative relief features and features on slopes very well visbile • contra: • not suitable for low positive relief features and low features on horizontal planes Openness • diffuse illumination from a homogeneously bright sphere centered on each pixel (Yokoyama et al., 2002; Doneus, 2013) (Yokoyama et al., 2002, Fig. 5) Openness • pro: • good depiction of relief details • contra: • loss of landscape forms positive openness: Openness • pro: • good depiction of relief details • contra: • loss of landscape forms negative openness: Accessibility • What is the diameter of the largest sphere that can be placed on the surface? (Miller, 1994) Accessibility • pro: • intuitively readable • relief detail as well as landscape forms • contra: • not suitable for horizontal planes • difficult to establish suitabel contrast stretch Local Dominance • How dominant is an observer with regards to the local surroundings? Local Dominance • pro: • good depiction of detail • contra: • different contrast stretch necessary for horizontal/sloping terrain Cumulative Visibility • What percentage of the area (within a given radius) is visible? Cumulative Visibility • pro: • good depiction of detail (when choosing low radius) • analytical tool for site and landscape interpretation • contra: • level of detail depends on chosen radius Multi-Scale Integral Invariants (MSII) • for n spheres with different diameters, centered on each DEM pixel, the percentage of each sphere above and below the DEM surface is computed • the resulting sets of n values for each pixel are interpreted as n-dimensional vectors, and the distance to a reference vector can be computed (Mara et al., 2010) Multi-Scale Integral Invariants (MSII) • pro: • good depiction of detail • contra: • loss of landscape shapes Laplacian-of-Gaussian • Laplacian filter: edge detection filter (Mlsna & Rodríguez, 2005) • pro: • good depiction of detail • fast algorithm • contra • loss of landscape shapes LiVT – an Open Source toolbox for DEM visualisation • stand-alone software that computes various visualisations • spatial filters (incl. Laplacian of Gaussian) • Shaded Relief • Sky-View Factor • Trend Removal • Local Relief Model • Exaggerated Relief • Local Dominance • Accessibility • Openness • MSII • Cumulative Visibility downloadable from: http://sourceforge.net/projects/livt/ • alternative freeware for some visualisations: Relief Visualisation Toolbox downloadable from: http://iaps.zrc-sazu.si/en/svf Geomorphological traces of conflict through the ages • (violent) conflict has been present throughout history • geomorphological impacts have changed over time Prehistoric to early modern conflict • mostly defensive structures/earthworks: ramparts, moats • fortification = conflict? • examples: • Neolithic and Bronze Age hilltop fortifications • Iron Age oppida • Roman limes • medieval fortifications • early modern fortifications Prehistoric to early modern conflict • Inca fortress Sacsayhuaman (Cusco, Peru) point density map (photogrammetric point cloud) Prehistoric to early modern conflict • Iron Age oppidum „Heidengraben“ Shaded Relief Sky-View Factor Prehistoric to early modern conflict • Roman limes Prehistoric to early modern conflict • medieval Prehistoric to early modern conflict • early modern: Philippsburg (War of Polish Succession, 1733-1738) Shaded Relief Prehistoric to early modern conflict • early modern: Philippsburg (War of Polish Succession, 1733-1738) ccLRM &Relief Shaded Shaded Relief Prehistoric to early modern conflict • early modern: Philippsburg (War of Polish Succession, 1733-1738) Shaded Relief Local Dominance Primary traces of modern industrial warfare • mass-produced, powerful explosives and delivery to the target • bomb and mine warfare • trenches, tank barriers WW II in Baden-Württemberg: bunkers, trenches, bomb craters „Westwall“ / „Siegfried Line“ Clusters of bomb craters Debris mounds Bunker remains • built 1936-1940 Tank barriers and trenches • c. 3500 structures >200 bunkers c. 60 km trenches c. 10 km tank barriers Hinterland • bomb craters Primary traces of modern industrial warfare • „Westwall“ near Hügelsheim Shaded Relief Local Dominance LD & SR Orthophoto Primary traces of modern industrial warfare • „Westwall“ near Müllheim Primary traces of modern industrial warfare • „Westwall“ near Müllheim Primary traces of modern industrial warfare • „Westwall“ near Rheinstetten Primary traces of modern industrial warfare • bomb craters (Ulm) Primary traces of modern industrial warfare • bomb craters (Esslingen) Secondary traces of modern industrial warfare • debris mounds • Birkenkopf (Stuttgart): 0,75 Mio. m3 • Grüner Heiner (Stuttgart): 4,7 Mio. m3 • Wallberg (Pforzheim): 0,55 Mio. m3 Birkenkopf Secondary traces of modern industrial warfare • debris mounds • Birkenkopf (Stuttgart): 0,75 Mio. m3 • Grüner Heiner (Stuttgart): 4,7 Mio. m3 • Wallberg (Pforzheim): 0,55 Mio. m3 Grüner Heiner https://plus.google.com/photos/+DieterThau/albums/5658092771702917521/5677561241283865058?pid=5677561241283865058&oid=103585898976472612049 Traces of warfare without war • military training and weapons testing facilities • conventional: Münsingen Local Dominance & Shaded Relief Traces of warfare without war • military training and weapons testing facilities • nuclear (Nevada test site) SR Traces of warfare without war • military training and weapons testing facilities • nuclear (Nevada test site) SVF SR Traces of warfare without war • military training and weapons testing facilities • nuclear (Nevada test site) SR LOG Traces of conflict sustenance • production of weapons etc. • war related mining • weapons production • infrastructure (railways etc.) • related housing etc. http://www.bergmannsverein-erfurt.de Conclusions • geomorphological traces of past conflict are common • from prehistory to modern • DEM visualisation techniques are important tools • variety of techniques with advantages and disadvantages • understanding of algorithms necessary for correct interpretation References Devereux, B.J., Amable, G.S., Crow, P., 2008. Visualisation of LiDAR terrain models for archaeological feature detection. Antiquity 82, 470–479. Doneus, M., 2013. Openness as visualization technique for interpretative mapping of airborne LiDAR derived digital terrain models. Remote Sensing 5(12), 6427-6442. Hesse, R. 2010. LiDAR-derived Local Relief Models – a new tool for archaeological prospection. Archaeological Prospection 17, 67–72. Imhof, E., 2007. Cartographic relief representation. English language edition edited by H.J. Steward. Redlands: ESRI Press. Mara, H., Krömker, S., Jakob, S., Breuckmann, B., 2010. GigaMesh and Gilgamesh – 3D Multiscale Integral Invariant Cuneiform Character Extraction, In: Artusi, A., Joly-Parvex, M., Lucet, G., Ribes, A., Pitzalis, D. (eds.), The 11th International Symposium on Virtual Reality, Archaeology and Cultural Heritage VAST (Paris, France, 2010), pp. 131–138. Miller, G., 1994. Efficient algorithm for local and global accessibility shading. Computer Graphics Proceedings, Annual Conference Series SIGGRAPH, 319–325. Mlsna, P.A., Rodríguez, J.J., 2005. Gradient and Laplacian edge detection. In: Bovik, A.C. (ed.), Handbook of image and video processing. 2nd. edition. Elsevier, Amsterdam. pp. 535–553. Rusinkiewicz, S., Burns, M., DeCarlo, D., 2006. Exaggerated Shading for depicting shape and detail. ACM Transactions on Graphics (Proceedings SIGGRAPH) 25(3), 1199–1205. Yokoyama, R., Shirasawa, M., Pike, R.J., 2002. Visualizing topography by openness: a new application of image processing to digital elevation models. Photogrammetric Engineering & Remote Sensing 68(3), 257–265. Zakšek, K., Oštir, K., Kokalj, Z., 2011. Sky-View Factor as a relief visualisation technique. Remote Sensing 3, 398–415. LIDAR data: LGL/LAD Baden-Württemberg