The measure of accuracy is

Accuracy is measured as the deviation from true reading compared with the observed reading. Accuracy of a measured value tells how close the measured value is to the actual value. Absolute error is the deviation of a reading from the actual or true reading.

∙ Accuracy is measured as the deviation from true reading compared with the observed reading. Accuracy of a measured value tells how close the measured value is to the actual value. 
∙ Absolute error is the deviation of a reading from the actual or true reading.
∙ Relative error is defined on true error, as the difference of a value of the true or actual value divided by the actual value. 
∙ Whereas percentage error is expressed in terms of percentage, i.e. by multiplying the relative error by 100, it is called percentage error. Both relative and percentage error give a quantitative analysis of the deviation from the true value.
∙ For example in 2 separate experiments with true value 1000m and 1m have absolute error as 0.1m. Now the relative error in these cases will be 0.999 and 0.9. So absolute error fails to tell us the correct measure of accuracy and relative or percentage error takes the win.