An illustration of the utility of state plane‐coordinate systems

In the minds of most persons there exists a psychological reaction against approximations. Approximations smack of rule of thumb. They introduce accidental errors that may accumulate and they are frequently dangerous if not used with thorough appreciation of their limitations. In the field of surveying and mapping, the measurements made in the field must be checked by geometry and reduced to a consistent geometric figure. As the shape of the Earth is not yet completely determined, any geometric check of field-measurements is bound to introduce a certain approximation. If the approximation is small enough, that is, considerably less than the probable resulting error, no harm can result.