Constant bearing, decreasing range (CBDR):
A term in navigation which means that some object, usually another ship viewed from the deck or bridge of one’s own ship, is getting closer but maintaining the same absolute bearing. If this continues, the objects will collide. Constant bearing means there is no relative lateral motion of an object, and the object appears to be fixed in position. As the range decreases, unless a change is made, there will be a collision.
The chief and I drilled it into the new Operations Specialists when we were teaching Maneuvering Board (MB). I surprised my men when I took over as CIC Officer in that I could do MB better than anyone other than the Chief. I guess it is one of those things that you either get or don't get.
When I started standing bridge watches, I was paired with the Weapons Officer. He taught me to do MB approximations in my head. It's a neat trick to speed up maneuvering to station.
SpyNavy
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)
Yet, when you are plotting to overtake, intercept, or rendezvous with another vessel, CBDR is what you plot first, then convert the relative motion needed to true course and speed.