Computer Vision‐based Orthophoto Mapping of Complex Archaeological Sites: The Ancient Quarry of Pitaranha (Portugal–spain)

Abstract

Ancient quarries are intriguing archaeological sites, but their detailed recording is complex. This paper presents a cost-effective approach to mapping of the Roman quarry site of Pitaranha (Portugal-Spain). First, aerial photographs were acquired using a radio-controlled digital reflex camera attached to a Helikite, which allowed the acquisition of the necessary low-altitude aerial footage in the very unstable wind conditions above the quarry. Using computer vision algorithms, the resulting set of photographs was semi-automatically transformed into a Digital Surface Model (DSM) and a corresponding orthophotograph. Besides focusing on the acquisition and processing method, this paper evaluates the accuracy of the generated products. The orthophotograph proved to be satisfactorily accurate for 1:200 hard-copy mapping.

Mapping with strings attached: Kite aerial photography of Durai Island, Anambas Islands, Indonesia

“…This degraded PhotoScan's ability to detect tie points automatically in water areas, so it was necessary to manually create approximately 200 tie points in order to include these areas in the model. These sources of error are not common to all projects that employ KAP and PhotoScan or similar software; others (e.g., Doneus et al, 2011;Verhoeven et al, 2012;Westoby et al, 2012), in addition to the two previously noted, have mitigated or avoided these sources of error by using more accurate positioning instruments or by modeling terrestrial areas, exclusively, where access allows a more homogeneous distribution of GCPs.…”

“…In contrast to the heavy plate and film cameras of the nineteenth and early twentieth centuries, today's lightweight digital cameras make KAP a practical means of collecting large-scale aerial imagery using consumer-grade equipment. Imagery collected via KAP has been used in a variety of scientific applications, for example to investigate forest cover and stream channel characteristics (Aber, Sobieski, Distler, & Nowak, 1999); to create digital elevation models (DEMs) for studying geomorphological processes (Marzolff & Poesen, 2009;Smith, Chandler, & Rose, 2009); and to create maps of vegetation canopy structure (Dandois & Ellis, 2010), the geomorphology of periglacial features (Boike & Yoshikawa, 2003), archaeological sites (Doneus et al, 2011;Kersten & Lindstaedt, 2012;Verhoeven, Taelman, & Vermeulen, 2012), intertidal rocky shores (Bryson, Johnson-Roberson, Murphy, & Bongiorno, 2013); and coral reefs (Scoffin, 1982). Other platforms for collecting aerial photographs include balloons, poles, and unmanned aircraft systems (UASs).…”

Coastline Zones Identification and 3D Coastal Mapping Using UAV Spatial Data

“…However, such small changes are not distinguishable at the spatial resolutions generally obtained using manned aircraft and satellite systems. Furthermore, the high level of automation, the ease of deployment, the ease of survey repeatability, and the low running costs of UAVs in comparison with other traditional remote sensing methods, allows for frequent missions that provide spatial datasets with a resolution of less than 5 cm and a high temporal repetition due to the ease of survey deployment [12,22,23]. Georeferenced orthophotos and digital surface models (DSMs) are used to measure and depict the morphology of a beach in 2D and 3D, which allows the assessment of changes to the beach due to extreme wave phenomena [6].…”

Terrestrial Laser Scanning in the Age of Sensing

“…The current major shift in 3D mapping and 3D modeling is due to proven computer vision technologies based on Structure from Motion (SFM) and Dense Stereo Matching (DSM) algorithms (Verhoeven 2011;Verhoeven et al 2012;De Reu et al 2013;De Reu et al 2014). SFM and DSM proved to be reliable technologies that can be used to process large datasets of aerial photographs captured by uncalibrated digital cameras mounted on lightweight aircrafts flying GPS waypoint missions.…”