Aerial Photography for Archaeology

Monte Alban in southern Mexico

Learning Objectives What are advantages of aerial archaeology? What platforms are used for aerial archaeology? What are soil marks, shadow marks, and crop marks, and how are they used to find sites? What are some of the difficulties encountered when using aerial imagery for archaeology?

How can aerial photography contribute to archaeological research? “It is a common opinion that an aerial archaeologist is sitting in an aeroplane, trying to discover archaeological sites and to take a few nice photographs of them.” (http://www.univie.ac.at/Luftbildarchiv/intro/aa_aaint.htm)

Partly true…but aerial archaeology is more useful than that… Many archaeological sites have been severely damaged by land use – like plowing or urban development, or by natural processes like erosion. An important goal of archaeology is to find sites over large areas quickly and cheaply so that they can be preserved rather than destroyed or exploited Air surveys are an efficient way to accomplish this.

5 sites identified in one aerial photograph near Hornsberg, Austria (University of Vienna photo)

Other functions of aerial archaeology Big picture can allow archaeologists to learn about the relationships between sites and between a site and its environment. Signs of roads and trails connecting sites Remnants of old waterways Vegetation relationships with sites Associations of sites with particular landforms, etc. (e.g., sand dunes in Wyoming)

Neolithic circular ditches in southern Austria (University of Vienna photo)

Linear roads radiating from Chaco site in NM contrast with modern roads that follow topography more (from a TIMS image)

Another view of Chaco linear road features (NASA)

Applications, continued… Sites can be mapped effectively from the air to provide archaeologists with a guide for ground excavation

Roman villa (“lumps and bumps”) as seen at ground level in farmer’s field – difficult to tell something was there and farmer had no idea that it was an entire villa. Image by Ashley Dace: Creative Commons

Site continues into another field but obscured by different vegetation Plow disturbance of rock pile used for building Same Roman villa as seen from the air – site discovered from air in 1979 associated with pot shards found in 1977. Original walls 60 cm below surface.

Map of the villa created from the air photo and ground survey (http://www.villa-rustica.de/villa/indexe.html)

Partially restored villa

Archiving Aerial images also provide an archive of site characteristics that can be a valuable record of sites in their original condition Site configuration Surrounding features (e.g., ancient roads, etc.) Can serve as a permanent record of the undisturbed site “Nazca monkey,” Peru (from Wikipedia)

History of aerial photography for archaeology Balloon flights in early 1900s 1906 – Air photos of Stonehenge from military balloon Cameras attached to kites Open seated biplanes in 1920s and 30s O.G.S. Crawford in England active in this period and said to be the “father of aerial archaeology” P.A. Poidebard active at same time in Syria World War II pilots documented sites that they noticed Aerial archaeological survey became more systematic in the 1960s

1931 air photo of Braunsberg, Austria (University of Vienna photo) Circular forts

Ring Fort in Ireland

Platforms used for archaeolgical photos Manned fixed winged aircraft Manned helicopters Kites Balloons Ultralight aircraft Unmanned aircraft (UAVs) YouTube video: Drone Archaeology

Photo features useful for identifying sites Shadows of features (shadow marks) Differences in soil color (soil marks) Differences in height and color of crops (crop marks) Differences in susceptibility to frost (frost marks) Aerial view gives an archaeologist the perspective necessary to integrate clues over large areas to see pattern that might not be visible on the ground.

Shadow marks in New Mexico

Shadow marks in Wyoming – rocks point to a pass (Photo ©Rita Donham)

Crop marks: Signs of old walls in Moravia (Photos from University of Vienna, Austria)

Soil marks in Austria (University of Vienna photo)

Challenges and problems with air photo interpretation for archaeology Site visibility affected by many factors: Soil type Vegetation Climate Time of day or year when photos taken Sometimes only major features visible—or none at all expressed clearly at surface Some sites hidden in caves, under cliff overhangs, etc.

Aerial Archaeology with Google Earth New tools like Google Earth provide ability to do aerial archaeology of anywhere on earth Somewhat resolution-limited for non-populated areas Ability to tilt for terrain visualization

Summary Aerial photography is widely used for archaeological surveys, site mapping, site context and archiving Discovery of sites relies on clues – differences in soils, vegetation, topography Modern tools like Google Earth provide easy access to aerial archaeology Identification of sites can help preserve them—especially important as human developments expand globally