  We present a detailed analysis of the distance determination for one
intermediate Velocity Cloud (IVC G139.6+47.6) from the ongoing DDO IVC Distance
Project. Stars along the line of sight to G139.6+47.6 are examined for the
presence of sodium absorption attributable to the cloud, and the distance
bracket is established by astrometric and spectroscopic parallax measurements
of demonstrated foreground and background stars. We detail our strategy
regarding target selection, observational setup, and analysis of the data,
including a discussion of wavelength calibration and sky subtraction
uncertainties. We find a distance estimate of 129 (+/- 10) pc for the lower
limit and 257 (+211-33) pc for the upper limit. Given the high number of stars
showing absorption due to this IVC, we also discuss the small-scale covering
factor of the cloud and the likely significance of non-detections for
subsequent observations of this and other similar IVC's. Distance measurements
of the remaining targets in the DDO IVC project will be detailed in a companion
paper.
