Methods of determining the true dip, or velocity, or both when the velocity is constant are described in the literature. When the sines of the angles of dip are known for two spreads in line with the shotpoint, and at right angles, the true dip can be found exactly (Nettleton, 1940; p. 294–295; and others). An exact extension of this result to two spreads not at right angles is simple, although apparently the equations have not been published. A slightly more general case in which at least two detectors are assumed to be in line with the shotpoint can also be solved exactly by elementary means. The general case in which no two detectors are in line with the shotpoint has apparently not been published. For the special cases mentioned, the present treatment is of greater generality, since the detectors here are not required to be in a level plane, which seems to be a requirement of previous methods. The present work is general in part through being three-dimensional and including the dip. The wave front is not assumed to be planar.