In this blog we will post terms and themes of related terms and their definitions that come from the The Glossary of Mapping Sciences with commentary. In the hope that by discussing the meaning of words we come to deeper understanding and more meaningful usage.
There are over 100 different terms with the word error in them in the Glossary of Mapping Sciences. Mapping Professionals and Scientists are and should be careful to document known error in their many different tasks related to the process of mapping and analysis. Below are some of our favorite errors!
error 1. The difference between the measured value of a quantity and the theoretical or defined value of that quantity: ε(error) º y (measured) ‑ y (theoretical). 2. The difference between an observed or calculated value of a quantity and the ideal or true value of that quantity. Logically, definitions (1.) and (2.) are distinctly different. In practice, they are equivalent except for the second definition's allowing calculated values to be used instead of measured values. 3. The difference between an approximate number and the correct number. 4. The difference between the theoretical or defined value of a quantity and the measured value of that quantity: ε (error) º y (theoretical) ‑ y (measured). This definition differs from the first definition only in changing the sign of the error.
error, absolute The value, taken without regard to sign, of the difference between some value of a quantity and the true value of that quantity.
error, actual 1. The measured value of a physical quantity minus the true value of that quantity. 2. The sum of all those systematic and random errors which have not been eliminated from the final, adopted, measured value.
error of commission That error introduced in a computation by using incorrect data or incorrect theory.
error of observation The difference between the measured value of a quantity and a value adopted as representing the ideal or true value of that quantity. Errors of observation are composed of either one or both of two general classes of error: accidental errors and systematic errors. Constant errors are sometimes placed in a third class but are more often included among the systematic errors as they should be. Errors of observation are also classified according to their origin as external errors, instrumental errors, and personal errors. The algebraic sign of the error of observation is determined from the equation: error of observation = measured value ‑ adopted (ideal) value. The term error of observation is dropping out of use and is being replaced by measurement error.
error of omission An error introduced into a computation by leaving out pertinent data or by omitting terms of an equation.
error of representation The error committed by assuming that one member of or sample from a statistical population is a valid representative of that population. In particular, in the analysis of data on gravity, the error committed by using the value of gravity at one or more points in a region instead of using the average value of gravity in the region. The term is also used in this way with respect to gravity anomalies.