  We developed the tool GEM-FIND that allows to constrain the morphology and
brightness distribution of objects. The software fits geometrical models to
spectrally dispersed interferometric visibility measurements in the N-band
using the Levenberg-Marquardt minimization method. Each geometrical model
describes the brightness distribution of the object in the Fourier space using
a set of wavelength-independent and/or wavelength-dependent parameters. In this
contribution we numerically analyze the stability of our nonlinear fitting
approach by applying it to sets of synthetic visibilities with statistically
applied errors, answering the following questions: How stable is the parameter
determination with respect to (i) the number of uv-points, (ii) the
distribution of points in the uv-plane, (iii) the noise level of the
observations?
