week 2 Flashcards
(21 cards)
What are the three types of errors in surveying measurements?
Gross errors, systematic errors, random errors
What are gross errors and how can they be minimized?
high or low values compared to other measurements, mainly due to an observer’s inexperience. They can be minimised by repeating measurements.
What characterizes systematic errors in surveying?
always has the same magnitude and sign resulting in a bias from the true value
How can systematic errors be minimised?
By maintaining and calibrating instruments properly and following correct measurement procedures.
What defines random errors in measurements?
vary in sign and magnitude, are unavoidable
What is accuracy in the context of measurements?
a measure of reliability defined as the difference between the true value and the most probable value (MPV).
How is the most probable value (MPV) determined?
MPV is usually the arithmetic mean of a set of observations.
What is the probable error (residual) in measurements?
The difference between the MPV and each observation.
What is the true error in measurements?
The difference between the true value of a quantity and the value obtained by an observation.
What is the relationship between accuracy and errors?
Accuracy is affected by systematic and gross errors, however its not known but can be estimated from residuals.
How is precision defined in surveying?
a measure of repeatability and can be numerically defined.
What is the difference between precision and accuracy?
Precision refers to the repeatability of measurements, while accuracy refers to how close a measurement is to the true value. (reliability)
What does a high precision indicate about probable errors?
indicates small probable errors (residuals).
What is the significance of the standard deviation in measurements?
indicates the amount of variation about a central value and reflects uncertainty in the measuring process.
What are outliers in a data set?
very different values from the rest of the values in a set of repeated observations outside ±3σ.
What is the standard error (SE) in measurements?
the mean of a sample describing average observation errors.
How does the number of observations affect the standard error?
it decreases as the number of observations increases.
What is the law of error propagation in surveying?
determines how errors in measurements translate into errors in the final result.
What does a tall thin curve in a normal distribution indicate?
It indicates high precision with small scatter of measurements.
What does a flatter curve in a normal distribution indicate?
It indicates low precision with larger random errors.
What is the significance of the arithmetic mean in a normal distribution?
The central value around which the distribution of measurements is symmetrical.
