What’s up, kids! Today we want to teach you about something called ‘constant bearing, decreasing range‘, a fun fact that may actually save your life!
But first, let’s take a look at this little LiveLeak GIF!
Close call, huh? That definitely left a skidmark! Now look at the gif again and try to spot the black car as early as possible.
Notice that in the beginning of the GIF, the black car doesn’t seem to move relative to the black bushes in the background? That should have been a big sign that a crash was imminent.
The phenomenon is called constant bearing, decreasing range. According to Wikipedia (c)onstant bearing, decreasing range is 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 relative bearing. If this continues, the objects will collide.
Us, non-sailor-folk, who are used to driving automobiles, normally are able to detect the possible risk of a collision with implicit reference to the background (e.g., the street, the scenery, the landscape, etc.) At sea the sea surface removes this vital visual clue. The CBDR technique helps seamen determine their position relative to each other when fewer visual references are available.
The thing is, it’s also pretty useful while driving. When a vehicle is moving perpendicular to you at high speed, always check the background. If the vehicle is moving backwards relative to the background, it will pass behind you. If it is moving forward relative to the background, it will pass in front of you. If the vehicle doesn’t seem to move relative to the background: well, congratulations, you are officially on a collision course!