This guideline is restricted to scanning probe microscopes and their calibration. A scanning probe microscope is a serially operating measuring device which uses a probe of adequate fineness to trace the surface of the object to be measured exploiting a local physical interaction (such as the quantum-mechanical tunnel effect, interatomic or intermolecular forces, evanescent modes of the electromagnetic field) with the probe and the object to be measured being displaced in relation to one another in a plane (hereinafter referred to as the x-y-plane) according to a defined pattern, while the signal of the interaction is recorded and can be used to control the distance between probe and object to be measured. In this guideline signals are considered which are used for the determination of the topography (hereinafter called "z-signal").