ESO Imaging Survey I. Description of the survey, data reduction and reliability of the data

This paper presents the first data evaluation of the ESO Imaging Survey (EI S), a public survey being carried out by ESO and member states, in preparat ion for the VLT first-light. The survey goals, organization, strategy and o bservations are discussed and an overview is given of the survey pipeline d eveloped to handle EIS data and produce object catalogs. A report is presen ted on moderately deep I-band observations obtained in the first of four pa tches surveyed, covering a region of 3.2 square degrees centered at alpha s imilar to 22(h)40(m) and delta = -40 degrees. The products available to the community, including pixel maps (with astrometric and photometric calibrat ions) and the corresponding object catalogs, are also described. In order t o evaluate the quality of the data, preliminary estimates are presented for the star and galaxy number counts, and for the angular two-point correlati on function obtained from the available data. The present work is meant as a preview of the final release of the EIS data that will become available l ater this year.