In this paper, we present methods for determining the measurement noise and residual flatness of areal surface topography-measuring instruments. The methods are compliant with draft international specification standards on areal surface texture. We first introduce the international standards framework and then present current methods based on averaging and subtraction to isolate the measurement noise and residual flatness from the sample surface topography. These methods are relatively difficult to apply and time consuming in practice. An alternative method is presented based on thresholding and filtering techniques. This method is simple to apply in practice. Traceability and measurement uncertainty are discussed.