A substrate shape measuring device, including: a substrate support to support a substrate having a main surface, the main surface of the substrate when supported by the substrate support substantially extending in a first plane; one or more sensor assemblies, each including a light emitter to emit light along a light axis substantially parallel to the first plane and a light sensor arranged to receive the light; and a processing device arranged to determine a shape of the substrate, wherein the substrate shape measuring device is constructed to measure with the one or more sensor assemblies in at least a first measurement direction with respect to the substrate substantially parallel to the first plane and a second measurement direction with respect to the substrate substantially parallel to the first plane.