  This is the fourth in a series of papers that aim both to provide reasonable
orbits for a number of eclipsing binaries and to evaluate the expected
performance of Gaia of these objects and the accuracy that is achievable in the
determination of such fundamental stellar parameters as mass and radius. In
this paper, we attempt to derive the orbits and physical parameters for three
eclipsing binaries in the mid-F to mid-G spectral range. As for previous
papers, only the Hp, Vt, Bt photometry from the Hipparcos/Tycho mission and
ground-based radial velocities from spectroscopy in the region 8480-8740 A are
used in the analyses. These data sets simulate the photometric and
spectroscopic data that are expected to be obtained by Gaia, the approved ESA
Cornerstone mission to be launched in 2011. The systems targeted in this paper
are SV Cam, BS Dra and HP Dra. SV Cam and BS Dra have been studied previously,
allowing comparisons of the derived parameters with those from full scale and
devoted ground-based investigations. HP Dra has no published orbital solution.
SV Cam has a beta Lyrae type light curve and the others have Algol-like light
curves. SV Cam has the complication of light curve anomalies, usually
attributed to spots; BS Dra has non-solar metallicity, and HP Dra appears to
have a small eccentricity and a sizeable time derivative in the argument of the
periastron. Thus all three provide interesting and different test cases.
