  We propose a method to compute optimal control paths for autonomous vehicles
deployed for the purpose of inferring a velocity field. In addition to being
advected by the flow, the vehicles are able to effect a fixed relative speed
with arbitrary control over direction. It is this direction that is used as the
basis for the locally optimal control algorithm presented here, with objective
formed from the variance trace of the expected posterior distribution. We
present results for linear flows near hyperbolic fixed points.
