Editing Underwater archaeology (section)

=== Position fixing ===
Knowing the location of an archaeological site is fundamental to being able to study it. In the open sea there are no landmarks, so [[position fixing]] is generally achieved using [[GPS]]. Historically, sites within sight of the shore would have been located using [[Navigational transit|transects]]. A site may also be located by visually [[Position fixing|surveying]] some form of marker (such as a [[buoy]]) from two known (mapped) points on land. The depth of water at a site can be determined from charts or by using the depth sounding [[sonar]] equipment that is standard equipment on ships. Such sonar can often be used to locate an upstanding structure, such as a shipwreck, once GPS has placed the research vessel in approximately the right location.