Learn About Underwater Archaeology

Documenting a Shipwreck

Field Research: Site Reconnaissance (Phase I)

Archaeologists need to know where sites are located on a very broad scale (county or state wide, for example) before they can begin to analyze sites individually. For preservation purposes, archaeologists have to know where and what a site is, how sensitive it may be, and what its archaeological and historical significance is before deciding how best to protect it. A Phase I survey records the basics of an archaeological site; it is often used to compile an "inventory" of wrecks for a designated area.

After determining the boundaries of an area to be surveyed, archaeologists must decide what method should be used to locate a site. In modest depths, a visual survey may be suitable if the remains of a wreck are exposed and the visibility is good. Shallow sites may also be spotted from boats, aircraft, or aerial photographs. However, most Phase I surveys require the use of some type of remote sensing equipment.

Resting in only a few feet of water, the City of Glasgow in Sturgeon Bay is easily spotted from an airplane

Remote sensing equipment ranges from fish-finders, to WWII surplus sonar, to modern sophisticated side scan sonar, sub-bottom profilers, and magnetometers. Remotely operated vehicles (ROVs) can also be used for visual-remote sensing at extreme depths.

Using sound waves that are sent and received by a device
towed behind a boat, side-scan sonar produces a picture
of the lake bottom--in this case an entire schooner. Click
on image for a close-up of the shipwreck
Learn More About Side-Scan Sonar