The first challenge facing archaeologists is finding the traces of human action. Survey: an archaeological survey maps the physical remains of human activity. The most obvious reason for carrying out an archaeological survey is to discover sites. Archaeological surveys must be designed with the goals of the project in mind. Often sites are so deeply buried that no artifacts are visible on the surface. Erosion can also complicate the interpretation of survey results. Stream channels have cut through archaeological sites and redeposited material far downstream. In situ: archaeological material is considered to be in situ when it is found in the place where it was originally deposited. In locations where there is heavy brush coverage, actually seeing artifacts can be extremely challenging. There are areas where one is walking on a "carpet of artifacts" - a situation that is problematic because one has to decide what to pick up and record. : an archaeological survey maps the physical remains.