(1) The square root of the average of the sum of the squares of the differences between (a) a set of measured or calculated values and a (b) set of corresponding correct values, divided by the average value of the set. i.e., relative accuracy is equal to the accuracy divided by the average value of the set. This is a useful quantity because it is dimensionless and independent of the units in which the measurements were made.

(2) A quantity expressing the effect of random errors on the location of one point or feature with respect to another. In particular, (a) an evaluation of the effect of the random errors in points on a map with respect to the graticule, excluding any errors in the graticule or the coordinate system of the graticule; or (b) an evaluation of the effect of random errors in determining the location of one point on a map with respect to another point on the same map.