Abstract: Methods for assessing the result of a surface treatment carried out on a workpiece by particle blasting are disclosed. It is generally common to known automatic methods that they directly determine the covered portion of the surface. Proceeding from the usual definition of the usual 98% degree of coverage as “completely blasted” results in an error in the determination of the corresponding area of 1% to a distortion of the measurement result by 0.98%. In the disclosed method measuring points are identified as not hit by a particle of the particle beam when both a detected surface level is above a level located about a predetermined height threshold value lower than a target level, and a detected gradient falls below a predetermined gradient threshold value.