Regional archaeological surveys must devise classification schemes that allow for meaningful comparison between features mapped throughout the survey area. In the Upper Colca Project, some artifact classes had radiating distributions that created special problems when devising comparable categories. This situation is best explained through an example that illustrates the challenges of consistent data recording.

The radial attenuation problem in artifact densities can be observed most dramatically in obsidian concentrations throughout the survey region as one departs from the Chivay source. In such situations, the human eye is easily misled by large concentrations of artifacts because the eye is attuned to the presence of contrasting or unusual materials, an issue that makes consistent sampling methods all the more important. In this example, the field crew would readily observe single flakes of obsidian far from the obsidian source, while at the source area itself a given obsidian flake was common place and obsidian densities were relatively deprioritized. Yet in the obsidian source area a flake of chertwas notable as it provided contrast. While these contrasts are meaningful: it is important that one might find a flake of chert at the obsidian quarry, far from the river where chert is usually found, such features should be mapped and observed separately with observations indicating that this is a-typical for the area. Ample effort should also be given to mapping features that aretypical to the area for faithful representation of general distributions.

This example illustrates a major methodological challenge for archaeological survey that exists in both conventional and digital recording systems. A systematic sampling strategy is the most cost effective way to describe the common features found in a region, because random samples can be extrapolated to the larger population. These distinctions in artifact identification correspond to two types of survey differentiated by Banning (2002: 27-38) as "statistical survey" and "prospection survey", as will be discussed in more detail below. Attributing the finds in the database based on the type of survey strategy that was employed permits a more consistent depiction of broader features of the landscape in later analysis.