1998A&A...331..934B

This is the first in a series of papers devoted to the determination of Galactic structure from the new homogeneous catalog of photographic RGU field star data in fourteen high-latitude directions. We give a general description of the motivation for this work, the construction of the observational data base, and the structural Galaxy models designed for its analysis. In particular, we provide a concise yet comprehensive account of the statistical methodology used for determining reliable constraints to the model parameters. Preliminary results obtained from the first-half sample of seven fields are discussed to demonstrate the significance of the approach. Our best models suggest that the thick disk component has a local density of 5.4±1.5% relative to the thin disk, an exponential scale height of 1.15±0.15kpc, and mean metallicity <[M/H]≳-0.6 dex with dispersion σ_<[M/H]>∼0.4dex. However, because the present data cannot exclude the existence of a vertical metallicity gradient d[M/H]/dz~-0.10±0.10dex/kpc, a sharper picture of the thick disk metallicity structure must await the analysis of the full-survey data in 14 fields.