also used (although amplified) to deflect the control surfaces that steer the missile, thereby making missile velocity vector rotation proportional to line of sight rotation. Although this does not result in a rotation rate that is always exactly proportional to the LOS-rate (which would require a constant airspeed), this implementation is equally effective. The basis of proportional navigation was first discovered at sea, and was used by navigators on ships to avoid collisions. Commonly referred to as Constant Bearing Decreasing Range (CBDR), the concept continues to prove very useful for conning officers (the person in control of navigating the vessel at any point in time) because CBDR will result in a collision or near miss if action is not taken by one of the two vessels involved. Simply altering course until a change in bearing (obtained by compass sighting) occurs, will provide some assurance of avoidance of collision, obviously not foolproof: the conning officer of the vessel having made the course change must continually monitor bearing lest the other vessel does the same. Significant course change, rather than a modest alteration, is prudent. International Regulations for Preventing Collisions at Sea dictate which vessel must give way but they, of course, provide no guarantee that action will be taken by that vessel. See also Motion camouflage Bibliography Yanushevsky, Rafael. Modern Missile Guidance. CRC Press, 2007. . References Navigation Missile guidance