Uncovering archaeological landscapes at Angkor using lidar

Abstract

Previous archaeological mapping work on the successive medieval capitals of the Khmer Empire located at Angkor, in northwest Cambodia (∼9th to 15th centuries in the Common Era, C.E.), has identified it as the largest settlement complex of the preindustrial world, and yet crucial areas have remained unmapped, in particular the ceremonial centers and their surroundings, where dense forest obscures the traces of the civilization that typically remain in evidence in surface topography. Here we describe the use of airborne laser scanning (lidar) technology to create high-precision digital elevation models of the ground surface beneath the vegetation cover. We identify an entire, previously undocumented, formally planned urban landscape into which the major temples such as Angkor Wat were integrated. Beyond these newly identified urban landscapes, the lidar data reveal anthropogenic changes to the landscape on a vast scale and lend further weight to an emerging consensus that infrastructural complexity, unsustainable modes of subsistence, and climate variation were crucial factors in the decline of the classical Khmer civilization.

Keywords: Southeast Asia; resilience; sustainability; urbanism; water management.

Fig. 1.

An overview of the lidar acquisition areas in northwest Cambodia (background data courtesy of the Shuttle Radar Topography Mission).

Fig. 2.

An oblique view of Angkor Wat and its immediate environs. Upper layer: Digital orthophoto mosaic, with elevation derived from the lidar digital surface model at 1-m resolution. Lower layer: extruded lidar digital terrain model, with 0.5-m resolution and 2× vertical exaggeration. Red lines indicate modern linear features including roads and canals.

Fig. 3.

The central area of Angkor, showing the “walled city” of Angkor Thom above Angkor Wat. Upper: lidar digital terrain model, with 1-m resolution. Red lines indicate postmedieval linear features including roads and canals; other features are Angkor era. Lower Left: conventional high-resolution satellite imagery of the central area, showing archaeological topography obscured by forest. Lower Right: previously documented (prelidar) archaeological features in the central area (2, 4).