For a nice overview of the method employed by PKAP in another context check out this informative page by PKAP's Field Director David Pettegrew.
|NARRATOR: Later, the seasoned team goes into the field to begin collecting artifacts and expand their grid. Each unit is forty meters square and assigned a number, which will be affixed to all artifacts collected within its perimeter. In this way, artifacts sent to the museum for analysis can be tracked based on their unit of origin, and provide an accurate model of their distribution across the site. This is also helpful if artifacts ever have to be returned to the site.
WILLIAM CARAHER: The downside of doing a regular grid is occasionally you’ll get units with really divergent environmental conditions. What we have here is a unit that has two different visibilities. The southern part of the unit unfortunately is in a deeply, relatively recently, deeply plowed field where you can see almost everything on the surface. The northern part of the unit, however, is unfortunately cut but not plowed grain stubble, which provides zero visibility. So, Mike will find pottery, and Suzie, Greg, and Katie who worked in the northern part of the unit will find no pottery because they couldn’t see the surface of the ground.
BRIAN WILLIS: Which way is my line going?
DAVID PETTEGREW: Look back on a line parallel with me forty meters. So look at the flag forty meters over from me.
NARRATOR: Dr. Caraher, acting as today’s team leader doesn’t just sit and watch the walkers. He’s busy completing forms with environmental data. This includes recording the surface visibility, soil type, and location of a walked unit in relation to all known features. And when the walkers have completed counting and collecting artifacts from a unit, the leader records their artifact counts for the purpose of computing density.
The team bags and tags all their finds with a label designating the unit number and the date it was recovered. This not only provides an accurate depiction of the site and their finds, but also a record of their collection methodology.