Data Collection: Reconnaissance & Survey

ANTH 235,

DATA COLLECTION: RECONNAISSANCE & SURVEY

Reconnaissance refers strictly to locating and identifying archaeological sites (“putting spots on a map”).

Survey is undertaken to record as much as possible about archaeological sites without excavation.

“Off-site” or “non-site” evidence: plow marks, surface scatters of artifacts, field boundaries, roads, irrigation canals, quarries and mines, etc.

Landscape archaeology

Discovering archaeological sites & features

(ground reconnaissance & aerial reconnaissance)

documentary sources, maps and place-names, salvage archaeology (also known as rescue archaeology)

In the past few decades, reconnaissance has developed from being simply a preliminary stage in fieldwork (looking for appropriate sites to excavate) to an independent line of inquiry – an area of research in its own right.

There are two kinds of ground reconnaissance: unsystematic and systematic

Reconnaissance and excavation are not mutually exclusive activities. Excavation tells us a lot about a little part of a site, and can only be done once, whereas reconnaissance tells us a little about a lot of sites, and can be repeated.

AERIAL RECONNAISSANCE & REMOTE SENSING

What is revealed by aerial photographs?

Earthworks: banks and associated ditches or stone-walled features. Usually revealed from the air as shadow-marks. Time of day and season are obviously important.

Traces of ditch-and-bank fortification at Ivolga, a third-century BCE fortress in southern Siberia, are barely visible even under optimal conditions (oblique lighting, low vegetation, no deep snow). Features such as these are often more visible in aerial photos than they are on the ground.

Soil-marks: reveal the presence of buried ditches, banks, or foundations by changes in sub-soil color. They mostly occur in agricultural zones, so many sites of this type have been or are being destroyed.

Circular defensive (?) structure in central Poland revealed by soil-marks. A modern dirt road runs diagonally through the lower left corner of the image.

Crop-marks: develop when a buried wall, ditch, or road either decreases or enhances crop growth by affecting availability of water and nutrients through changing the depth and composition of soil.

Linear ditch at Alfred’s Castle, Oxfordshire,England revealed by crop-marks.

Larger-scale patterns: aerial photography can put seemingly random distributions of sites in association by establishing systems of interconnecting roads or relationships between sites and local resources (water, raw materials, arable land; “Nazca Lines,” Peru, below).

RECENT DEVELOPMENTS & NEW DIRECTIONS:

digital image capture – resolution still rather low for archaeological applications, but great near-term potential
digital enhancement of imagery
manipulation of spatial data and imagery in a Geographic Information System (GIS)
new photographic films, especially those with emulsions sensitive to the infrared portion of the spectrum

REMOTE SENSING FROM HIGH ALTITUDE:

two principal sources of data: various satellite systems and the American Space Shuttle
two principal types of data: photography and radar
among satellites, the American Landsat and WorldView, the French SystèmeProbatoire d’Observation de la Terre (SPOT), the Russian Ikonos, and the Japanese Radarsat systems are among the most useful
problems: low spatial resolution(variable, but mostly no better than 10 meters. There is great potential here: current technology available within the intelligence community allows ground resolution on the order of only 5-10 cm!) and very high cost

SUB-SURFACE DETECTION:

probes: probing the soil with rods or borers. Still very common.
non-destructive techniques: geophysical remote sensing devices that either pass energy of various kinds through the soil to “read” what lies below the surface, or measure variability in the earth’s magnetic field.

approaches include: echo-sounding, ground-penetrating radar, electrical resistivity, metal detectors, and magnetic survey (below).

(Above): Magnetic survey being undertaken at the Iron Age Pen y Cloddiau Hill Fort, near Nannerch, Wales using a dual sensor Magnetic Gradiometer. The instrument consists of two fluxgates very accurately aligned to nullify the effects of the Earth’s magnetic field. Readings relate the difference in localized magnetic anomalies with the general magnetic background. The instrument consists of two high-stability fluxgate gradiometers suspended on a single frame. Each sensor has a one meter separation between the sensing elements giving a strong response to deeply buried anomalies.

See:

A sophisticated gradiometer/magnetometer array being used

on archaeological survey

underwater archaeology: sonar, magnetic anomaly detection, sub-bottom profiling (radar)

Hull-mounted multibeam sonar (left) and

towed side-scan sonar array (right)

The Stalinets-class Soviet submarine, S7, sunk by the Finnish submarine Vesihiisi in summer 1942. In July 1998, the S7 was located with side-scan sonar at a depth of 40-45 meters off Söderarm in the Stockholm archipelago. The 78-meter long sub is intact except for the stern, where the Vesihiisi’s torpedo impacted. The conning tower and the stern hatches are closed, and no one has entered the vessel thus far. Before she was hit, the S7 had closed all interior hatches and was preparing to dive, so portions of the interior, now a grim grave, may still be dry. (Sonogram by Sture Hultquist)