Spaced-receiver scintillation measurements are modeled applying scintillation theory together with model spectral representations of nonfrozen turbulent media. The effects of velocity distribution of scatterers, diffusion of irregularities and velocity gradient across the scattering layer on parameters derived from spaced-receiver scintillation experiments are studied. Both correlation and dispersion analyses are considered. The results from modeling are compared with observational data from the equatorial region. It will be demonstrated that self-consistent models can be constructed in interpreting the data and information about the drift velocity field in the ionosphere can be obtained from spaced-receiver experiments.