Friday, May 16, 2008

Data Processing

Our approach to the fields south of town should prove very useful as we are collecting accurate, precise information on everything we find. The down side of this approach, however, is large numbers of data that have to be processed to produce detailed maps with topographic contours. Typing in long series of numbers all day, especially on gloomy, rainy days can be trying. But we'll not feel sorry for ourselves because tomorrow we are back in the sun having fun.

A brief note on my use of the terms 'accuracy' and 'precision.' If I were to say that there are 290 million people in the United States, that probably would be accurate. If I said there were 281,089, 004 people in the United States in 2005, that would be more precise, but inaccurate. (It is impossible to achieve that degree of precision and absolute accuracy in counting members of a population...there are too many people dying and being born at any one time, quite apart from the other problems inherent in any census system.)

In mapping artifacts in the field, our instrument calculates to the nearest hundredth of a foot, but if the person holding the rod with the prism over the artifact doesn't have that rod perfectly plumb, the error could easily exceed the degree of precision. If I were to estimate the accuracy with which we map artifacts, I'd say we have each object within three inches (0.25 ft) of its true location. Given the fact that the field has been plowed repeatedly over the centuries, the error probably is irrelevant. The clustering of materials still tell us where the sites are.

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