Thursday, September 02, 2010

Ground Penetrating Radar (GPR) Technology on Space Archaeology

Two NASA Earth scientists are using satellite data and ground penetrating radar (GPR) technology to map and protect areas of archaeological interest for an excavation project in central Turkey. Scientists Compton Tucker from NASA's Goddard Space Flight Center in Greenbelt, Maryland, and Joe Nigro, who works at Goddard through Science Systems and Application Inc., hope to use the data to pinpoint the position of tombs and artifacts prior to excavation, protecting them from both natural elements and looting. In the past, NASA radar has been used on satellites and spacecrafts to detect ice deposits and to explore deep canyons on the moon’s surface.

"The radar assists in excavation by helping archaeologists identify areas where there are features under the ground, but GPR is also used as a non-invasive technique so that the site doesn't have to be excavated," said Nigro, a GIS specialist and archaeologist by training.

"Archaeology is inherently labour intensive, and thus expensive in terms of time and money, so we rarely get to excavate an entire site. GPR and other geophysical techniques allow us to collect data on parts of the site we might otherwise not be able to investigate," said Philip Mink II, a GIS manager and staff archaeologist from the University of Kentucky, Department of Anthropology. "These investigations may locate archaeological features such as houses, tombs, burials, trash and storage pits, and ceramic firing areas that can be targeted for excavation given the limited money and time field archaeologists often face."

Mink, who has no affiliation with the Gordion project, believes that GPR is one of the most diverse and useful tools of all geophysical techniques used in archaeology.

State of the art software will be used to process the 3-D radar data and construct virtual representations of the buried features. According to Mink, the amount of data collected per unit area surveyed by GPR definitely surpasses the other geophysical techniques because it is collecting data constantly at a variety of depths.

GPR also allows the scientists to carry out their work while remaining culturally sensitive to the land, preventing the disturbance of burial sites or relics from the past, an activity that may be considered taboo by some indigenous groups.

From satellite images and digital elevation data, the team of space archaeologists will anchor and standardise reference points using GPS. They will compare land measurements with computed GPS data to correctly locate archaeological features by creating a network of points partially based on existing maps. Aerial and balloon photography from previous years will also serve to better locate trenches and structures from various excavation seasons.

In addition, the team is also using remote sensing technology to detect the dynamic changes in the environment caused by both natural processes and human practices, such as climate and agriculture. These environmental changes may be hidden to the naked eye.

"We don't want to be limited by our eyes, so we use electromagnetic spectrum radar to look beneath the surface," Tucker said. To observe land use and land cover change in Central Turkey from 1950 to 2010, the project will also examine NASA Landsat satellite images. The imagery will be processed and analysed to map natural and human-induced vegetation changes. For each time period, the Landsat data will categorically be divided by areas with variations of water, forest, pastures and cultivation. Apart from contributing to the continued preservation of Turkey's cultural legacy, the data from these NASA images will further promote sustainable development, according to Tucker and Nigro.

Both men anticipate the techniques developed in the Gordion Project will be applicable to many other archaeological sites with similar mapping problems such as the Hassanlu site in Iran and Tikal in Guatemala.

Provided by NASA.


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