14
Execution of Surveys;
 Sources of Error
•Errors may be characterized as random, systematic, or blunders
–Random error represents the effect of unpredictable variations in the instruments, the environment, and the observing procedures employed
–Systematic error represents the effect of consistent inaccuracies in the instruments or in the observing procedures
–Blunders or mistakes are typically caused by carelessness and are detected by systematic checking of all work through observational procedures and methodology designed to allow their detection and elimination