Using Unmanned Aerial Systems (UAS) for Remote Sensing of Archaeological Sites

BY RACHEL QUIST


Unmanned vehicles are becoming more widely available both in the military and civilian sectors for their usefulness for remotely acquiring a variety of data. Unmanned Aerial Systems (UAS), previously referred to as Unmanned Aerial Vehicles (UAV), are integrated ground, air, and data systems in which an aircraft (fixed wing or rotary) are either remotely piloted or operates autonomously and can perform a number of missions, including reconnaissance and remote sensing.

Beyond the military’s interest in UAS’s, the civilian sector has become increasingly aware of these systems and due to lower tech options; UAS’s have become useful in a number of scientific discipline studies.

RQ-8A FIRE SCOUT VERTICAL TAKEOFF AND LANDING TACTICAL UNMANNED AERIAL VEHICLE (VTUAV) SYSTEM. SOURCE: U.S. NAVY PHOTO BY PHOTOGRAPHER’S MATE 2ND CLASS DANIEL J. MCLAIN

Archaeological researchers are an early adopter of remote sensing technology but until the early part of the twenty-first century data was primarily limited to aerial/satellite imagery and photogrammetry. These methods were rather successful for a number of projects, most notably investigations of the geoglyphs of Nazca, Peru, but were still rather limiting in many ways.

Examining the Nazca case study, these archaeological features are highly unique and unusual and have been a bit of a mystery for the last century, largely due to the difficulty of recording these large features. The Nazca lines are huge, some measuring 200 meters, and are combinations of lines, trapezoids, stars, human figures, and animal figures. The geoglyphs are made by removing reddish pebbles of the high desert plateau and exposing the light colored ground underneath.

FIGURE IS KNOWN AS THE DOG, AN EXAMPLE OF NAZCA GEOGLYPHS LOCATED IN THE NAZCA DESERT, A HIGH ARID PLATEAU THAT STRETCHES 53 MILES BETWEEN THE TOWNS OF NAZCA AND PALPA ON THE PAMPAS DE JUMANA. SOURCE: COLEGTA (WIKIMEDAI COMMONS).

In a study published in 2000, Grün et.al used digital photogrammetric technology and integrated their data intovector and raster GIS data. This was the first time that these archaeological features were recorded using a GIS approach. Unfortunately, their study encountered a technological limitation of the computers at the time; their computer memory was limited to 64 MB which was not enough to render some of their graphics and data.

A few years later, in 2004, Eisenbeiss published a study in which a mini unmanned aerial vehicle was used for photogrammetric recording and documentation of a previously identified heritage site in Peru, Pinachango Alto. This study used a Copter 1B from Survey-Copter equipped with GPS/INS stabilized system, an onboard Cannon D10/D60 camera, and a ground control station by weControl. The flight plan was developed with predefined points and stopped and once programmed into the helicopter the flight path was automatically flown.

The project was able to successfully map the archaeological site and to render a 3D model of the settlement but they still had their share of technological difficulties. Their conclusions and recommendations noted that UAS’s used to map heritage sites should be able to fly longer than 15 minutes, which in their case required attaching a larger gas tank and then increasing engine power to carry the heavier payload.

In more recent years, a wide variety of UAS systems have been developed to address these early problems of duration, payload weight, and computer memory. In addition, GPS, LiDAR, photography, and wireless data integration have also improved allowing for viewing of real-time imagery from UAS’s for a period of several hours.

Thermal infrared photography from UAS’s is another improvement that has allowed archaeologists to see previously unknown and subtle features on top and beneath the surface landscape. Linear features such as prehistoric roads and canals can be easily detected as well as some subsurface features and burials using thermal infrared photography. Due to these improvements in the technology a number of archaeological survey and recording projects around the globe have used unmanned aerial systems to locate and map archaeological sites. In fact, the technique is becoming so widespread it has earned the name “aerial archaeology.”

Despite these improvements, use of unmanned aerial systems is largely restricted to being used to locate and record very large archaeological sites and generally those sites that contain remains of structures. These types of archaeological sites, although very impressive and widespread throughout the world, are not the most common site type. More typically, archaeologists record artifact concentrations associated with specific activity types in the past; these may include hunting sites, tool resharpening stations, toolstone quarrying, plant gathering and processing stations, and ceremonial locations. At this point in time, the best method to locate these discrete clusters of small artifact remnants is with the unaided human eye during a pedestrian survey.

Other uses for UAS technology are quickly becoming evident and entering the civilian sector through private corporations marketing directly to specific industries. Current and future applications of UAS’s will include forest fire detection, fire fighting, emergency mountain rescue, avalanche survivor search, crop dusting, pollution monitoring, natural disaster monitoring, delivery of emergency medical/food supplies, road traffic surveillance, poaching patrol, and weather data and research.

References:
Eisenbeiss H., 2004. A mini unmanned aerial vehicle (UAV): system overview and image acquisition. International Workshop on “Processing and visualization using high-resolution imagery”.

Grün, A, Bär, S., Beutner, S., 2000, Signals in the sand: 3-D recording and visualization of the Nasca geoglyphs. PFG, Vol. 6

Source: GIS Lounge - Maps and GIS