Astrometric Plate Reduction with Orthogonal Functions and Milli-Arcseconds Accuracy in Deep Proper Motion Surveys

We have been doing a sample survey in UBV photometry and proper motions as part of an investigation of galactic structure and evolution. The programme is based on Schmidt plates (from OCA, Tautenburg, Palomar and ESO Schmidt telescopes) digitized with the MAMA machine (CAI, Paris). The high astrometric quality of the MAMA gives access to micronic accuracy (leading to $<$ 2 mas per year) on proper motions with a 35 years time base. The high proper motion accuracy for faint star probes in wide-areas give access to the properties of star samples out of the solar neighborhood. We have analyzed components of the UVW galactic space motions resulting from the accurate proper motion surveys. The kinematical distribution of F and G--type stars have been probed to distances up to 2.5 kpc above the galactic plane. We have derived the constrain on the structural parameters of the thin and thick disk components of the Galaxy.