Blunder

As gross errors (English blunder ), a measurement error is referred to in measurement technology and the natural sciences, the usual scattering of the measured values ​​significantly exceeds by an oversight or an external influence.

Typical examples are meters error while reading a tape measure or degree of error in angles and temperatures. Sometimes it also comes confusion of measuring and destination points or to sign errors of data reduction. External disturbances can be, for example, the yielding of the substrate, an undiscovered axis tilt or shift on the meter, or a sudden air turbulence.

During the inevitable small measurement error ( in DIN now referred to as measurement error) are randomly distributed and therefore statistically compensate for an averaging or notional adjustment, this is not the case with gross errors. They distort the results and the computational model on one side ( as well, but more as a systematic error ) and therefore can not be subjected to the adjustment. They can be recognized, inter alia,

• By an over- determination - that is, by excess measurements that reveal the gross error by a contradiction. Examples are the measurement of blocking measures between sampled points
• The measurement of sagittal heights on curves or curved surfaces
• Control with intersections of straight lines ( see Alignment )
• Comparison with previous measurements;

• Views the rest of deviations ( residuals ). Gross errors make evident from the fact that they usually exceed the 3- times standard deviation
• Specific omission of individual " suspicious " measurements until the mean error within the expected ranges;