H. Summary

Consider a surveyor in 30 years interpreting a property description written by you today. Your description says "200 feet to an iron pipe" and the surveyor finds an iron pipe at 210.5 feet. Is his distance compatible with the one you specified?

We communicate two things when recording a measurement or a computation result. First is a magnitude (size); second is a resolution (accuracy). 200 and 200.00 are both the same magnitude, but have different resolution. That's why we use significant figures: to provide the user with an indication of accuracy. This is important because often our numbers must stand on their own without benefit of our being around to explain them.

Part of the surveyor’s job is error budget manager. Accuracy is a function of how well errors are controlled. Knowing that errors cannot be completely eliminated, we develop field procedures which allow many systematic errors to cancel or at least be minimized. Other systematic errors are dealt with computationally, either in instrumentation or software.

Random errors are minimized by using appropriate equipment, knowledgeable personnel, and careful measuring techniques. Remaining error affects our final product, be it a point location, line dimension, or parcel area. An appreciation of how errors behave allows the surveyor to state the final product to an appropriate accuracy level.

Too often we allow software to dictate accuracy. A computer, while an efficient computational tool, has limited decision making capabilities. The surveyor must be able to look at results generated by software and decide to what level of accuracy they should be shown. This comes from an understanding of errors in the measurements used to obtain those results.