4 ms·

It's not just for falling objects. In ship navigation this is known as Constant Bearing, Decreasing Range. https://en.wikipedia.org/wiki/Constant_bearing,_decr

It's not just for falling objects. In ship navigation this is known as Constant Bearing, Decreasing Range. https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_range https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_r...

toss1 2y ago
Yup! Also applies to cars on intersecting roads especially at odd angles; if it's staying in the same spot in the windshield/side window, one of you needs to change speeds or you'll have an unscheduled rapid disassembly at the intersection. It's also a real problem for certain intersection angles where vehicles or bicycles with unfortunate timing will be obscured behind the A-Pillar until nearly too late. There was an article (iirc) on HN years ago about just such an intersection repeatedly injuring/killing bicyclists. I once had to seriously threshold brake at an off-angle intersection to avoid a fire truck running a red light, when the timing/speed/distance/angle all lined up to hide the entire truck behind the A-Pillar for a few seconds approaching the intersection.
psunavy03 2y ago
And in aviation. Aircraft tracking across your canopy/windscreen? Usually NBD. Aircraft staying in the same spot on your canopy/windscreen? Potentially a Very Bad Thing.
- rconti 2y ago
  And on the racetrack: car in front of you out of control? Drive to where it is, because it won't be there for long.
  - toss1 2y ago
    Ha! yup, heard that a looong time ago, but not from any racer. Having qualified for racing licenses and won championships in several types of racing including road racing, it's actually more complicated than that; you're looking at what direction the wheels are pointing, which wheels are on/off the pavement/grass and what'll hook-up or break-loose in the next seconds... e.g., if someone in front of you is two wheels off on the left side, and starts to turn back onto the track, he'll probably loop straight across the track in front of you and pound the right-side wall or sail across the right-side glass. I have pics of me absolutely threshold braking for exactly that situation, which looks like "huh?" in the first pic, then the next pic, I would have absolutely t-boned the guy if I hadn't braked so hard (and no, driving to where he was, half in the grass, wasn't an option). So, if you don't have any clues, and have a half second to make your choice, I suppose it's better than no rule of thumb, but I wouldn't rely on it as a primary technique.
- mncharity 2y ago
  For illustration, a midair collision[1], where the "same spot"s were regrettably obscured for both pilots. [1] https://www.youtube.com/watch?v=mT1omo5jBqs&t=116s https://www.youtube.com/watch?v=mT1omo5jBqs&t=116s
  - toss1 2y ago
    Wow - great illustration indeed!

toss1 2y ago

Yup! Also applies to cars on intersecting roads especially at odd angles; if it's staying in the same spot in the windshield/side window, one of you needs to change speeds or you'll have an unscheduled rapid disassembly at the intersection. It's also a real problem for certain intersection angles where vehicles or bicycles with unfortunate timing will be obscured behind the A-Pillar until nearly too late. There was an article (iirc) on HN years ago about just such an intersection repeatedly injuring/killing bicyclists. I once had to seriously threshold brake at an off-angle intersection to avoid a fire truck running a red light, when the timing/speed/distance/angle all lined up to hide the entire truck behind the A-Pillar for a few seconds approaching the intersection.

psunavy03 2y ago

And in aviation. Aircraft tracking across your canopy/windscreen? Usually NBD. Aircraft staying in the same spot on your canopy/windscreen? Potentially a Very Bad Thing.

rconti 2y ago
And on the racetrack: car in front of you out of control? Drive to where it is, because it won't be there for long.
- toss1 2y ago
  Ha! yup, heard that a looong time ago, but not from any racer. Having qualified for racing licenses and won championships in several types of racing including road racing, it's actually more complicated than that; you're looking at what direction the wheels are pointing, which wheels are on/off the pavement/grass and what'll hook-up or break-loose in the next seconds... e.g., if someone in front of you is two wheels off on the left side, and starts to turn back onto the track, he'll probably loop straight across the track in front of you and pound the right-side wall or sail across the right-side glass. I have pics of me absolutely threshold braking for exactly that situation, which looks like "huh?" in the first pic, then the next pic, I would have absolutely t-boned the guy if I hadn't braked so hard (and no, driving to where he was, half in the grass, wasn't an option). So, if you don't have any clues, and have a half second to make your choice, I suppose it's better than no rule of thumb, but I wouldn't rely on it as a primary technique.
mncharity 2y ago
For illustration, a midair collision[1], where the "same spot"s were regrettably obscured for both pilots. [1] https://www.youtube.com/watch?v=mT1omo5jBqs&t=116s https://www.youtube.com/watch?v=mT1omo5jBqs&t=116s
- toss1 2y ago
  Wow - great illustration indeed!