  We refine the gap size measurements of the disk surrounding the Herbig Ae
star HD 100546 in the N band. Our new mid-infrared interferometric (MIDI) data
have been taken with the UT baselines and span the full range of orientations.
The correlated fluxes show a wavy pattern in which the minima separation links
to a geometrical structure in the disk. We fit each correlated flux measurement
with a spline function, deriving the corresponding spatial scale, while
assuming that the pattern arises interferometrically due to the bright emission
from the inner disk and the opposing sides of the wall of the outer disk. We
then fit an ellipse to the derived separations at their corresponding position
angles, thereby using the observations to constrain the disk inclination to i
=47 +/- 1 degree and the disk position angle to PA =135.0 +/- 2.5 degree East
of North, both of which are consistent with the estimated values in previous
studies. We also derive the radius of the ellipse to 15.7 +/- 0.8 au. To
confirm that the minima separations translate to a geometrical structure in the
disk, we model the disk of HD 100546 using a semi-analytical approach taking
into account the temperature and optical depth gradients. Using this model, we
simultaneously reproduce the level and the minima of the correlated fluxes and
constrain the gap size of the disk for each observation. The values obtained
for the projected gap size in different orientations are consistent with the
separation found by the geometrical model.
