The requirements on the precision lengths and precision load measurement rise due to the rapid technical development, in particular of nanotechnologies and precision optics. According to the roadmap "Dimensional metrology for micro- and nanotechnology" of the European National Metrology Institutes (iMERA) 2 in the next few years "traceable 2D (3D) metrology at (sub)-nm accuracy over several 100 mm range" will be required.