Sometimes archeological field work requires more "unconventional" tools. When a shovel isn't able to reach deep enough, sometimes a backhoe is required to remove "overburden" (fill) that is too deep to remove by hand. Other times, the materials that are being looked for (such as Civil War battle artifacts) do not lend themselves to standard techniques such as STPs. In these instances, systematic metal detecting*, under the guidance of an NPS archeologist may be used. When searching for evidence of structures or foundations, gradiometer surveys (a gradiometer is a complex machine which detects magnetic variations below ground) or surface penetrating radar (SPR) surveys may be conducted to cover a large area in a fairly economical manner. Surveying equipment, such as a total station, may also be used to layout STPs or grids for gradiometer or SPR surveys.
All archeological investigations must be carefully structured and documented so that every aspect of the recovered data can be understood and analyzed. It is also important that methods and results be reproducible, to facilitate future research. Survey equipment such as total stations and GPS equipment help the archeologist produce accurate maps which can be used for follow-up in later field seasons.