The classification of errors are:
1. System error
System error, also known as measurable error or regular error, refers to the error caused by deviation from the specified conditions or measurement methods, which changes according to certain laws. The characteristics of this kind of error are: under the measurement conditions, the absolute value and sign of the error remain unchanged or change according to a certain law (the size and sign change according to a certain law). According to the regularity of error occurrence, system error can be divided into: constant error with unchanged error value and sign and variable error with changed error value and sign.
2. Random error
Random error, also known as undetermined error, refers to the error in which the absolute value and sign change in an unpredictable way when the same value is measured many times under actual measurement conditions. The regularity of this error is very complicated, so we can only find out the numerical relationship between the error size and the number of occurrences by statistical methods, that is, find out the distribution law of the error. When the number of measurements increases, the arithmetic mean of the error tends to zero.
From the perspective of probability theory and mathematical statistics, it can be considered that this error is a random event under the measurement conditions, and from the perspective of probability, it is a random change around the arithmetic mean (mathematical expectation) of the measurement results. To analyze this kind of error, we must understand its probability distribution law. Classical error theory holds that the probability distribution of random error is normal distribution, and on this premise, a statistical analysis method of random error is established.
3. Neglect of mistakes
Gross error, also known as gross error or operation error, refers to a kind of error that can not be measured correctly and leads to serious distortion of measurement results, and its error value exceeds the expected value under specified conditions. Neglect error is caused by negligence in measurement, mainly for three reasons:! The subjective negligence of the metrological personnel or the sudden change of objective conditions are not corrected in time, resulting in errors in reading, recording or calculation; The measuring instruments used are defective and the surveyors failed to find them; # The surveyor made an error when operating the measuring instrument.
According to the error theory, the gross error can be judged, and the measurement data containing gross error should be eliminated in data processing, otherwise the measurement results will be untrue, that is, there is a big deviation from the true value.