THE NEW BASEL HIGH-LATITUDE FIELD STAR SURVEY OF THE GALAXY - I - GENERAL INTRODUCTION, METHODOLOGY AND FIRST ANALYSIS

This is the first in a series of papers devoted to the determination o f Galactic structure from the new homogeneous catalog of photographic RGU field star data in fourteen high-altitude directions. We give a ge neral description of the motivation for this work, the construction of the observational data base, and the structural Galaxy models designe d for its analysis. In particular, we provide a concise yet comprehens ive account of the statistical methodology used for determining reliab le constraints to the model parameters. Preliminary results obtained f rom the first-half sample of seven fields are discussed to demonstrate the significance of the approach. Our best models suggest that the th ick disk component has a local density of 5.4 +/- 1.5% relative to the thin disk, an exponential scale height of 1.15 +/- 0.15 kpc, and mean metallicity [[M/H]] similar to -0.6 dex with dispersion sigma([[M/H]] ) -0.3 dex. However, because the present data cannot exclude the exist ence of a vertical metallicity gradient partial derivative[M/H]/partia l derivative z similar to -0.10 +/- 0.10 dex/kpc, a sharper picture of the thick disk metallicity structure must await the analysis of the f ull-survey data in 14 fields.