We describe the choice of parameters involved in designing a system in which an unmanned airborne vehicle using a camera relays image data to a nearby ship where a human, possibly with the help of a recognition system, is alerted to the possibility of a collision with a whale or other large marine mammal. A key constraint is that the system be inexpensive and, where possible, realized from off-the-shelf equipment. © 2003 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1525276) Subject terms: aerial imagery; collision avoidance; remote sensing; whales and dolphins; rotation- and scale-invariant detection; pattern-recognition application. r(0)5(x M(0),y M(0)). More generally, at time t.0, we denote the position of the MM by r(t). We assume that the MM can swim at a maximum speedVM . In Fig. 2, the MM is shown swimming in a direction specified by the anglef with respect to a vertical line. The distance from the MM to the ship at any time is denoted by d(t). Clearly d(0)5(x M 1y M ) 1/2 and d(t) 5$@xs(t)2x M(t)# 2 1@ y s(t)2y M(t)# 2 % 1/2 , where xs(t) 5Vst, y s(t)50, x M(t)5x M(0)1VMt sin f, and y M(t) 5y M(0)2VMt cos f. A collision at time t c requires that d(t c)50. From these observations, the time to a collision must satisfy the two equations