Constraining galactic structure parameters from a new extinction model and four star count samples

We propose a new 3-dimensional extinction model based on the COBE/IRAS all sky reddening map. Its application to globular and open cluster data evidences that the COBE/IRAS reddening map has an accuracy of 18%, but overestimates visual absorption by a factor of 1.16. This systematic error does not change with galactic latitude and opacity significantly. The implementation of the new extinction model has optimized our galactic structure and kinematic model to lowgalactic latitudes. Four star count samples distributed in different galactic directions have been compared with galactic model simulations. Numerical experiments allow us to constrain the radial distribution of the galactic disk. The disk scale length is found to be 2250 ± 50 pc and the displacement of the Sun from the galactic plane ZSun = 27.5 ± 6.0 pc.