This technique is a collective term that refers to various methods of survey that take place on the ground as opposed to in the air. This includes field walking and data recording, visual investigation of surface features or high densities of artifacts, and gathering information on a specific area for the mapping process. Using historical documents to locate potential sites and conducting salvage archaeology on a construction site are other methods of ground reconnaissance.
There are two types of surface surveying: unsystematic and systematic. The former involves field walking and recording locations of artifacts and surface features. Systematic surveying uses a grid system so that each section is investigated separately, resulting in a more thorough survey. Most modern survey is conducted systematically. Mapping and surface collection are two basic methods used in surface surveying.
In archaeology, site planning involves three main steps. First, a framework that encompasses the site must be built. Next, the area is plotted, using either the compass-pacing or the baseline-offset technique. Finally, leveling is used to measure the rise and fall of the area surface features. Surveyors often divide the area into triangles, with angles between 30 and 120 degrees to keep measurement errors minimal. Measurements are then checked independently to avoid unnecessary inaccuracies.
This refers to survey techniques that take place in the air. In aerial photography, a photographer and interpreter examine the terrain and features of photos to locate possible sites. Remote sensing refers to images taken from satellites and shuttles, used to trace large-scale features, such as the ancient levee systems in Mesopotamia. High-altitude radar mapping can be used to penetrate areas with heavy cloud cover or dense rainforests.
Survey techniques are determined by the nature of the site. A variety of specialized reconnaissance methods are used when dealing with sites located underwater. Archaeologists use other survey methods for collecting data from below the surface level or from areas surrounding a site. These techniques include radioactivity scanning, seismic surveying, magnetic surveying and geophysical surveying. Unlike the basic methods that can be used in surface surveying, these techniques require sophisticated instruments to collect information.