Aerial archaeology is the study of archaeological sites from the air. It is a method of archaeological investigation that uses aerial photography, remote sensing, and other techniques to identify, record, and interpret archaeological features and sites. [1] Aerial archaeology has been used to discover and map a wide range of archaeological sites, from prehistoric settlements and ancient roads to medieval castles and World War II battlefields.
Aerial archaeology involves interpretation and image analysis of photographic and other kinds of images in field research to understand archaeological features, sites, and landscapes. It enables exploration and examination of context and large land areas, on a scale unparalleled by other archaeological methods. The AARG (Aerial Archaeology Research Group) boasts that "more archaeological features have been found worldwide through aerial photography than by any other means of survey". [2]
Aerial archaeological survey combines data collection and data analysis. [3] The umbrella term "aerial images'" includes traditional aerial photographs, satellite images, multispectral data (which captures image data within specific wavelength ranges across the electromagnetic spectrum) [4] and hyperspectral data (similar to multi-spectral data, but more detailed).
A vast bank of aerial images exists, with parts freely available online or at specialist libraries. These are often vertical images taken for area surveys by aircraft or satellite (not necessarily for archaeological reasons). Each year a small number of aerial images are taken by archaeologists during prospective surveys. [5]
The origins of aerial photography, which led to the rise of aerial archaeology, began in the mid-19th century with early experiments in capturing landscapes from above. The French photographer Nadar (Gaspard-Félix Tournachon), who is credited with taking the first aerial photograph from a balloon in 1858 over the outskirts of Paris. [6] : 66 In America, a man named James Wallace Black, in 1860, became the first person to successfully take aerial photographs from a hot air balloon over Boston. Around the same time, Thaddeus Lowe, a scientist and aeronaut, also used balloons for military reconnaissance during the American Civil War.
In the years leading up to the First World War, several early attempts were made to use aerial photography for archaeological purposes, though they often faced significant technical and practical challenges. One of the earliest figures involved in this effort was Sir Henry Wellcome, a British-American pharmaceutical entrepreneur and philanthropist. In the early 1900s, Wellcome financed several archaeological expeditions in Sudan, where he employed aerial photography using a box kite to document excavations in Jebel Moya, Sudan. [7] : 14
Nevertheless, while the products of these efforts proved the potential value of aerial photographs for archaeological research, these early attempts to obtain usable photographs fell short. Camera technology of the time was insufficient, let alone the erstwhile methods for getting cameras into the air. [8]
The outbreak of World War I marked a critical turning point in the development of aerial archaeology. British and Belgian air forces pioneered the use of aerial photography for reconnaissance as early as 1914, marking the beginning of a systematic approach to aerial observations. [9] Aerial photography advanced rapidly due to its essential role in military reconnaissance. Both the Allies and Central Powers relied heavily on aerial photographs to map enemy positions and monitor battlefield activity. It was during this time that aerial photography techniques improved dramatically, particularly in terms of camera technology, altitude, and film quality. The use of specialized reconnaissance aircraft, which were equipped with advanced cameras, allowed for the collection of high-resolution images on a scale and precision previously unattainable.
Although aerial photography during the war was primarily a military tool, its application to archaeology was soon recognized. The thousands of aerial photographs captured over Europe revealed previously unknown archaeological features, such as crop marks, that were visible from the air but invisible from the ground. These images, primarily intended for military strategy, revealed unexpected archaeological features, especially in Europe. This discovery highlighted the potential of aerial photography not just for military purposes but also for archaeological discovery and documentation.
After the war, many of the techniques and technologies developed during the conflict were adopted by archaeologists. Figures like English archaeologist O.G.S. Crawford, who is widely considered the "father of aerial archaeology," were instrumental in applying wartime advances to peacetime archaeological research. Crawford recognized the potential of aerial photography for archaeological research and conducted extensive surveys of the English landscape from the air. He published numerous articles and books on the subject, laying the foundation for the development of aerial archaeology as a scientific discipline. Crawford's systematic use of aerial photography in the 1920s marked the beginning of modern aerial archaeology, building on the foundations laid by earlier pioneers and the technological leaps made during the war.
In the 1920s, Osbert Guy Stanhope Crawford emerged as a key figure in the development of aerial archaeology. Crawford recognized the potential of aerial photography for systematically documenting archaeological sites. His work in Britain and the Middle East demonstrated that aerial surveys could reveal features such as crop marks and soil disturbances that were undetectable from ground level. His pioneering efforts helped establish aerial archaeology as a legitimate and essential method within the broader field of archaeological research.
Major G. W. G. Allen was an English engineer who, after learning of the work Crawford was doing, he was inspired to use his own airplane around Southern England, taking photographs of the landscape. His work in documenting prehistoric landscapes and Roman roads in England marked a significant advancement in the application of aerial methods for archaeological surveys. [7] : 69–73 [10] : 22
Following the Second World War, advancements in aerial photography and imaging techniques significantly broadened the scope of aerial archaeology. The introduction of infrared photography and multispectral imaging enabled archaeologists to detect subtle variations in vegetation and soil, allowing for the identification of buried structures that would otherwise remain hidden. These technological innovations made it possible to conduct more detailed and accurate surveys, further enhancing the effectiveness of aerial archaeology.
In the post-war period, aerial archaeology expanded beyond Europe, becoming an invaluable tool for researchers working in regions with vast and difficult-to-access landscapes, such as the Americas, Africa, and Asia. In these areas, aerial surveys uncovered ancient civilizations and revealed the locations of significant archaeological sites, many of which had been previously unknown. The ability to survey large areas quickly and efficiently made aerial archaeology a critical tool for understanding diverse archaeological landscapes across the globe.
In recent years, the advent of drones, or unmanned aerial vehicles (UAVs), has revolutionized aerial archaeology. Drones offer greater flexibility and lower operational costs compared to traditional manned aircraft. With the ability to capture high-resolution images and access areas that are otherwise difficult to reach, drones have become an essential tool for modern archaeological surveys. The increased use of drones has made aerial archaeology more accessible to a broader range of researchers and has led to more frequent and detailed studies of archaeological landscapes.
Technological advancements such as LiDAR (Light Detection and Ranging) and photogrammetry have further enhanced aerial archaeology. LiDAR, in particular, is capable of penetrating dense vegetation to reveal features hidden beneath forest canopies, making it an invaluable tool for studying heavily forested regions. Photogrammetry, which allows for the creation of precise 3D models of archaeological sites, has enabled researchers to document and analyze sites with unprecedented accuracy. Together, these technologies have expanded the potential of aerial archaeology, allowing for more detailed and comprehensive analyses of archaeological sites.
Pioneers of aerial archaeology include:
Aerial archaeology plays a crucial role in discovering new archaeological sites and mapping their extent. By providing a bird's-eye view, aerial images can reveal subtle features and patterns that are often invisible from the ground. This is particularly valuable in areas with:
Aerial images provide a wealth of information for identifying and recording archaeological features. These include:
By carefully analyzing aerial images, archaeologists can identify, document, and interpret a wide range of archaeological features, providing valuable insights into past human activities and settlement patterns.
Aerial photographs provide the foundation for creating accurate and detailed site plans and maps. This involves:
These site plans and maps are essential for documenting archaeological sites, planning excavations, and managing cultural heritage resources. They provide a valuable record of the site's extent, features, and spatial context, aiding in interpretation and future research.
Photography is the most common method used in aerial archaeology. Archaeologists use specialized cameras and lenses to capture high-resolution images of the ground from aircraft or drones.
Aerial photographs can be captured from different angles, each offering distinct advantages for archaeological investigation:
The choice between oblique and vertical photography depends on the specific research questions and the characteristics of the site being investigated. Often, archaeologists utilize a combination of both techniques to gain a comprehensive understanding of the archaeological record.
Certain archaeological features are more visible from the air than on the ground due to their nature. A key concept behind interpretation in aerial archaeology is that formation processes affect site features differently after abandonment. For a site to be detected by a remote sensing method, one would expect alterations to the soil or subsoil e.g. ditches, pits, banks, mounds, walls etc. which often are visible in relief. [11]
Tiny differences in ground conditions caused by buried features can be emphasized by a number of factors and viewed from the air:
For a three-dimensional effect, an overlapping pair of vertical photographs, taken from slightly offset positions, can be viewed stereoscopically.
Beyond traditional aerial photography, archaeologists utilize a range of remote sensing techniques to investigate sites without physical excavation. These methods involve collecting data from a distance using specialized sensors that detect and record different forms of electromagnetic radiation. This information can reveal subsurface features, variations in vegetation, and other archaeological clues hidden from the naked eye. Digital data, for example, ALS, can be used effectively in "heavily automated workflows," [12] (a process that uses rule-based logic to launch tasks that run without human intervention), e.g. a six-year project using supervised automated classification to survey 35,000 km2 (14,000 sq mi) of Baden-Wurttemberg in Germany, identified as many as 600,000 possible sites. [12]
The NASA LANDSAT series (satellite observations) are often used in aerial archaeology. Renfrew and Bahn describes the techniques used as scanners that "record the intensity of reflected light and the infrared radiation from the earth surface and convert these electronically into photographic images." [13] LANDSAT images have helped in identifying large-scale features, such as an ancient riverbed running from the Saudi Arabian desert to Kuwait. [14]
SLAR (sideways looking airborne radar) is a remote sensing technique that records pulses of electromagnetic radiation from an aircraft. Richard Adams used SLAR to identify a matrix of possible Mayan water irrigation systems underneath the dense rainforest from a NASA aircraft. [15]
SAR (synthetic aperture radar) involves radar images that are processed to create high-resolution data. [15] This technique stands out, as weather conditions and nightfall do not affect its results. Renfrew and Bahn describe it as a "rapid non-destructive alternative to surface survey that does not involve the collection of artifacts." [16] It can be faster and less time-consuming than surface survey.
LiDAR (light detection and ranging) aka ALS (airborne laser scanning) uses laser scanner pulses to measure the distance to the ground and other objects. By emitting thousands of pulses per second and recording the time it takes for them to return to the sensor, LiDAR creates highly accurate 3D models of the Earth's surface. In archaeology, LiDAR is invaluable for:
In places yet to be documented (or where maps are considered confidential), satellite imagery is vital to providing base maps for excavation. [15] Satellite imagery offers a broad perspective, covering vast areas and providing valuable data for regional studies and landscape archaeology. Different types of satellites capture various wavelengths of light, providing information about:
One of the useful resources for accessing satellite imagery is Google Earth. This platform includes a range of different satellite and aerial images, such as the NASA LANDSAT series, Ikonos, QuickBird, GeoEye alongside more. [15]
The Cold War CORONA satellite photographs have been used extensively for base maps and provisional interpretation. [15] In contrast to other imagery, CORONA uses two images of the same feature to create a stereoscopic view, which can allow for more accurate examination and interpretation in 3D. [2]
Thermal imaging captures infrared radiation emitted by objects, revealing differences in temperature. In archaeology, this can be used to:
ASTER (advanced spaceborne thermal emission and reflection radiometer) is used to create maps of "land surface temperature, reflectance, and elevation." [16] It is attached to the side of satellite Terra and can be used to create digital elevation models.
These advanced imaging techniques capture data across a wide range of the electromagnetic spectrum, going beyond the visible light captured by traditional cameras.
For data analysis, aerial images must be analyzed and interpreted using specialized skill-sets. This includes an understanding of formation processes as well as contemporary history and landscape history. [17] Often aerial archaeology will be carried out using computer programmed (such as GIS) aiding interpretation. The raw data collected through aerial photography and remote sensing requires careful processing and interpretation to extract meaningful archaeological information. This involves:
Photogrammetry is a technique for creating 3D models from overlapping photographs. By analyzing the different perspectives captured in multiple images, specialized software can reconstruct the geometry of the scene. In archaeology, photogrammetry is used to:
Geographic Information Systems (GIS) are essential tools in modern archaeology, providing a powerful platform for managing, analyzing, and visualizing spatial data. In aerial archaeology, GIS plays a crucial role in:
Raw aerial images often require enhancement to improve their clarity and highlight archaeological features. Various digital image processing techniques are employed, including:
These image enhancement and analysis techniques are crucial for extracting meaningful information from aerial imagery, allowing archaeologists to identify subtle archaeological features and interpret their significance within the broader landscape.
Aerial archaeology, specifically LIDAR, was used to study Caracol, a Mayan city in Belize, dated to 550-900 AD. Archaeologists Arlen and Diane Chase, from the University of Central Florida, worked for 25 years in the dense tropical rainforest, managing to map 23 km2 (8.9 sq mi) of settlement. At the end of the dry season of 2009, they embarked on four continuous days of LIDAR flying, followed by three weeks of analysis by remote sensing experts. This allowed them to surpass the results of the prior 25 years, revealing over 177 km2 (68 sq mi) of city—a far larger area than expected. Furthermore, the landscape was modelled in 3D, leading to the discovery of possible new sites such as "ruins, agricultural terraces and stone causeways" [18] (to be investigated further for a greater understanding). We can thus see the impressive effect aerial methods can have on streamlining archaeological survey, and pushing the limits of what is possible.[ citation needed ]
Homs, Syria provides an example of how different types of satellite imagery can be used in combination. The site is based in an area notorious for its difficulties surrounding archaeological survey, as the diversity of terrain makes the detection of archaeological sites difficult. As a result, Homs is a perfect candidate for aerial reconnaissance. Modern agriculture often obscures remains through practices such as deep ploughing (which removes many levees and low-lying sites from the archaeological record). [14] Furthermore, vegetation of different types/densities frequently disguises sites, impeding site visibility.
The Homs projects combined the usage of CORONA, LANDSAT, IKONOS, and Quickbird imagery to observe "long-term human and environmental interactions" [14] and, more broadly, to assess the landscape, over an area of 630 quare kilometres that had no prior database of remains or aerial photography. Through fieldwork, the different applications and abilities of these satellite imagery techniques were revealed, highlighting the importance of using multiple methods of archaeological investigation together.
The LANDSAT imagery fell short when used for site detection and mapping, due to its lower resolution compared to Quickbird and IKONOS, but was most successful at characterizing the environment and visualizing rates of change. [14]
CORONA imagery successfully detected single-period sites, which could not be detected by IKONOS. Furthermore, CORONA imagery assisted in exposing ancient field systems, and crop marks within fields, revealing early watercourses. [14]
In this instance, visual detection and interpretation of satellite imagery proved more useful than processing LANDSAT imagery. [14]
Through interpretation archaeological sites were identified as tells with low-relief soil markings, "with remains ranging from small walls less than 1 m wide to large multi period settlements." [14] The projects as a whole demonstrated how valuable aerial archaeology is to archaeological survey, especially across terrains where other techniques are not possible.
In archaeology, excavation is the exposure, processing and recording of archaeological remains. An excavation site or "dig" is the area being studied. These locations range from one to several areas at a time during a project and can be conducted over a few weeks to several years.
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth and other planets. Remote sensing is used in numerous fields, including geophysics, geography, land surveying and most Earth science disciplines. It also has military, intelligence, commercial, economic, planning, and humanitarian applications, among others.
In archaeology, geophysical survey is ground-based physical sensing techniques used for archaeological imaging or mapping. Remote sensing and marine surveys are also used in archaeology, but are generally considered separate disciplines. Other terms, such as "geophysical prospection" and "archaeological geophysics" are generally synonymous.
Aerial photography is the taking of photographs from an aircraft or other airborne platforms. When taking motion pictures, it is also known as aerial videography.
Photogrammetry is the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena.
Cropmarks or crop marks are a means through which sub-surface archaeological, natural and recent features may be visible from the air or a vantage point on higher ground or a temporary platform. Such marks, along with parch marks, soil marks and frost marks, can reveal buried archaeological sites that are not visible from the ground.
Landscape archaeology, previously known as total archaeology is a sub-discipline of archaeology and archaeological theory. It studies the ways in which people in the past constructed and used the environment around them. It is also known as archaeogeography. Landscape archaeology is inherently multidisciplinary in its approach to the study of culture, and is used by pre-historical, classic, and historic archaeologists. The key feature that distinguishes landscape archaeology from other archaeological approaches to sites is that there is an explicit emphasis on the sites' relationships between material culture, human alteration of land/cultural modifications to landscape, and the natural environment. The study of landscape archaeology has evolved to include how landscapes were used to create and reinforce social inequality and to announce one's social status to the community at large. The field includes with the dynamics of geohistorical objects, such as roads, walls, boundaries, trees, and land divisions.
Archaeological science consists of the application of scientific techniques to the analysis of archaeological materials and sites. It is related to methodologies of archaeology. Martinón-Torres and Killick distinguish ‘scientific archaeology’ from ‘archaeological science’. Martinón-Torres and Killick claim that ‘archaeological science’ has promoted the development of high-level theory in archaeology. However, Smith rejects both concepts of archaeological science because neither emphasize falsification or a search for causality.
Environmental archaeology is a sub-field of archaeology which emerged in 1970s and is the science of reconstructing the relationships between past societies and the environments they lived in. The field represents an archaeological-palaeoecological approach to studying the palaeoenvironment through the methods of human palaeoecology and other geosciences. Reconstructing past environments and past peoples' relationships and interactions with the landscapes they inhabited provide archaeologists with insights into the origins and evolution of anthropogenic environments and human systems. This includes subjects such as including prehistoric lifestyle adaptations to change and economic practices.
In archaeology, survey or field survey is a type of field research by which archaeologists search for archaeological sites and collect information about the location, distribution and organization of past human cultures across a large area. Archaeologists conduct surveys to search for particular archaeological sites or kinds of sites, to detect patterns in the distribution of material culture over regions, to make generalizations or test hypotheses about past cultures, and to assess the risks that development projects will have adverse impacts on archaeological heritage.
In archaeology, an enclosure is one of the most common types of archaeological site – It is any area of land separated from surrounding land by earthworks, walls or fencing. Such a simple feature is found all over the world and during almost all archaeological periods. They may be few metres across or be large enough to encompass whole cities.
Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range. It can allow extraction of additional information the human eye fails to capture with its visible receptors for red, green and blue. It was originally developed for military target identification and reconnaissance. Early space-based imaging platforms incorporated multispectral imaging technology to map details of the Earth related to coastal boundaries, vegetation, and landforms. Multispectral imaging has also found use in document and painting analysis.
Geobotanical prospecting refers to prospecting based on the composition and health of surrounding botanical life to identify potential resource deposits. Using a variety of techniques, including indicator plant identification, remote sensing and determining the physical and chemical condition of the botanical life in the area, geobotanical prospecting can be used to discover different minerals. This process has clear advantages and benefits, such as being relatively non-invasive and cost efficient. However, the efficacy of this method is not without question. There is evidence that this form of prospecting is a valid scientific method, especially when used in conjunction with other prospecting methods. But as identification of commercial mines are invariably guided by geological principles and confirmed by chemical assays, it is unclear as to whether this prospecting method is a valid standalone scientific method or an outdated method of the past.
Aerial photographic and satellite image interpretation, or just image interpretation when in context, is the act of examining photographic images, particularly airborne and spaceborne, to identify objects and judging their significance. This is commonly used in military aerial reconnaissance, using photographs taken from reconnaissance aircraft and reconnaissance satellites.
Remote sensing techniques in archaeology are an increasingly important component of the technical and methodological tool set available in archaeological research. The use of remote sensing techniques allows archaeologists to uncover unique data that is unobtainable using traditional archaeological excavation techniques.
This page is a glossary of archaeology, the study of the human past from material remains.
Digital archaeology is the application of information technology and digital media to archaeology. It includes the use of digital photography, 3D reconstruction, virtual reality, and geographical information systems, among other techniques. Computational archaeology, which covers computer-based analytical methods, can be considered a subfield of digital archaeology, as can virtual archaeology.
Remote sensing is used in the geological sciences as a data acquisition method complementary to field observation, because it allows mapping of geological characteristics of regions without physical contact with the areas being explored. About one-fourth of the Earth's total surface area is exposed land where information is ready to be extracted from detailed earth observation via remote sensing. Remote sensing is conducted via detection of electromagnetic radiation by sensors. The radiation can be naturally sourced, or produced by machines and reflected off of the Earth surface. The electromagnetic radiation acts as an information carrier for two main variables. First, the intensities of reflectance at different wavelengths are detected, and plotted on a spectral reflectance curve. This spectral fingerprint is governed by the physio-chemical properties of the surface of the target object and therefore helps mineral identification and hence geological mapping, for example by hyperspectral imaging. Second, the two-way travel time of radiation from and back to the sensor can calculate the distance in active remote sensing systems, for example, Interferometric synthetic-aperture radar. This helps geomorphological studies of ground motion, and thus can illuminate deformations associated with landslides, earthquakes, etc.
Kweneng’ ruins are the remains of a pre-colonial Tswana capital occupied from the 14th to the 19th century AD in South Africa. The site is located 30km south of the modern-day city of Johannesburg. Settlement at the site likely began around the 1300s and saw its peak in the 14th century. The Kweneng' ruins are similar to those built by other early civilizations found in the southern Africa region during this period, including the Luba–Lunda kingdom, Kingdom of Mutapa, Bokoni, and many others, as these groups share ancestry. Kweneng' was the largest of several sizable settlements inhabited by Tswana speakers prior to European arrival. Several circular stone walled family compounds are spread out over an area 10km long and 2km wide. It is likely that Kweneng' was abandoned in the 1820s during the period of colonial expansion-related civil wars known as the Mfecane or Difaqane, leading to the dispersal of its inhabitants.
Aerial photograph interpretation is a method of extrapolating geological details of the ground surface from aerial images. It allows geologists to analyze the distinguishing geological features and structures, plant cover, past history of the site, soil properties, and topography of the study area. It is crucial in the early stage of a geological mapping as it is less time-consuming and offers important data at a minimal price. It is also commonly used in other industries such as forest management, environmental science, disciplines of engineering, and investigating aviation accidents.
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