My favorite application of dead reckoning is the early 80's Honda system to display the car location on a map. While testing the system, there were times where the car showed itself off of the road. After looking into it further, they learned the map maker had taken some liberties with the exact position of the road, and the vehicle was correct.
Interestingly, if you have good map data, the relative "shape" of you previous trajectory is enough to locate your position globally, without GPS, even without knowing where north is.
that's literally no different than what Google Maps does in my car while in CarPlay mode. It's like Apple neuters it and don't give it full gyro/compass data, because when driving it constantly moves the "car" anywhere from 90 to 270 degress and keeps it there for a few seconds until it figures this out again. I checked all possible permissions and still can't figure it out.
Never happens on the Apple Maps, although I have 0 trust in siri and apple maps, especially when we travel to europe, i feel like i'm an experiment for apple to see how much off straight forward route it can make me take.
I have the same thing happen on Google Maps - on top of my car just spinning in circles, it will also show up 100-300 feet to the right of the road I'm driving on, constantly doing navigation updates to the nearest street. When I unplug from carplay, it's fine, and back on the road, then when I plug it into the car it pops to the right again and starts doing updates.
Interesting. A number of years ago google maps on apple didn't behave that way. Then one trip I noticed my wife's maps were freaking out in a city with a lot of large curves and clover leaf onramps.
Of course my android with Google maps behaves as expected, though in a few places with stacked interchanges it can get confused if traffic is moving slow.
My favourite example of some humorous dead reckoning, from this old copypasta:
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The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't.
In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was.
The missile guidance computer scenario works as follows. Because a variation has modified some of the information the missile has obtained, it is not sure just where it is. However, it is sure where it isn't, within reason, and it knows where it was. It now subtracts where it should be from where it wasn't, or vice-versa, and by differentiating this from the algebraic sum of where it shouldn't be, and where it was, it is able to obtain the deviation and its variation, which is called error.
> the castaways had not seen any women in months, and based on the resulting unwanted attention, the indigenous people opted to evacuate before the English seamen became a problem.
Damn interesting has an amazing collection of high-quality podcast episodes with amazing story telling. They haven’t released new episodes in a while, but their back catalogue is worth investigating.
Alan Bellows here, author of this article, and founder of Damn Interesting. For years I kept the site going by working a part-time coding job, along with occasional contract work. Combined with donations to the site, this brought in enough income to survive, while allowing me to dedicate 5-6 hours per weekday to writing/editing/etc.
Early in the pandemic my job wrapped up, and when I went looking for a new part-time or contract gig, there was absolutely nothing. I networked and searched for a year and a half, and never found a single part-time opening. In the meantime, donations to the site were on a steady downward trajectory. I was burning through my savings at an alarming rate.
Eventually I had to take a regular full-time job just to have income again. I hoped I could find some plausible approach, but so far it's been unworkable. I also have a six year old, so evenings and weekends tend to be spoken for. And after the little one's bedtime, there's not much left in the fuel tanks. I'm approaching 50 now.
Maybe I'll find a part-time gig, or perhaps some anonymous wealthy benefactor will fund the site for a while. Both have happened before. If not, we may need to pack it up soon. 20 years is a pretty good run.
What I find remarkable is the way the Admiralty - a very imperfect system with multiple facets that are downright clownish is nevertheless principled as a whole when it comes to strategic interests - the nation's foes are harassed, leadership positions are manned by technically competent individuals, regulations are amended to incorporate major learnings and so on.
Also, the banality of how the system treats sailor lives as expendable is almost incomprehensible from a 21st century perspective.
My favourite dead reckoning anecdote[1] was there was this British naval captain who found himself in the Atlantic just a bit south-west of the Canary Islands in a lifeboat. He knew that the ocean currents would be against him and too strong to row against, so he set off for South America and made it there by rowing with the current and using dead reckoning to course correct.
[1] And this is from memory and a bunch of googling around hasn’t turned it up so pardon me if I get some details wrong.
It's an incredible story and deserves to be told. 1500miles at sea in an overloaded open lifeboat using stellar navigation and managed to save more than half of the people aboard. So they were sailing rather than rowing but other than that I had remembered it substantially correctly.
Transatlantic by dead reckoning alone sounds impossibly difficult. Captain Bligh navigating 3500 nautical miles from Tahiti to Kupang in an open boat after being mutinied against was a celebrated feat of navigation, and he had the aid of a compass and a pocket watch.
So long as one can see the sun and stars reasonably frequently, I imagine a competent navigator could estimate his latitude and know which way is West accurately enough to stay in the trade winds and make landfall along Brazil's coast, which I suppose was McVicar's only hope, given the extreme shortage of water and rations.
I really enjoyed The Wager by David Grann about this story. Grann was also the author of Killers of the Flower Moon, which was made into the movie of the same name by Martin Scorsese, and Scorsese is now making The Wager into a film, although I don't think they've even settled on a release year yet.
Readit News
Previous discussion: https://news.ycombinator.com/item?id=38135979
https://ad-publications.informatik.uni-freiburg.de/GIS_paths...
Never happens on the Apple Maps, although I have 0 trust in siri and apple maps, especially when we travel to europe, i feel like i'm an experiment for apple to see how much off straight forward route it can make me take.
Of course my android with Google maps behaves as expected, though in a few places with stacked interchanges it can get confused if traffic is moving slow.
Map makers make mistakes on purpose. This way they know when someone copies their maps. They look for these little tiny "mistakes".
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The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't.
In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was. The missile guidance computer scenario works as follows. Because a variation has modified some of the information the missile has obtained, it is not sure just where it is. However, it is sure where it isn't, within reason, and it knows where it was. It now subtracts where it should be from where it wasn't, or vice-versa, and by differentiating this from the algebraic sum of where it shouldn't be, and where it was, it is able to obtain the deviation and its variation, which is called error.
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[0] https://www.youtube.com/watch?v=_LXen-07Qds
chef kiss
Early in the pandemic my job wrapped up, and when I went looking for a new part-time or contract gig, there was absolutely nothing. I networked and searched for a year and a half, and never found a single part-time opening. In the meantime, donations to the site were on a steady downward trajectory. I was burning through my savings at an alarming rate.
Eventually I had to take a regular full-time job just to have income again. I hoped I could find some plausible approach, but so far it's been unworkable. I also have a six year old, so evenings and weekends tend to be spoken for. And after the little one's bedtime, there's not much left in the fuel tanks. I'm approaching 50 now.
Maybe I'll find a part-time gig, or perhaps some anonymous wealthy benefactor will fund the site for a while. Both have happened before. If not, we may need to pack it up soon. 20 years is a pretty good run.
Also, the banality of how the system treats sailor lives as expendable is almost incomprehensible from a 21st century perspective.
Worth the read.
And for HN in particular, there is an ancestral link from the suffering crew of the ill-fated ship to the category of jobs that we have today.
I won't spoil it. But here is a clue: A.L.
[1] And this is from memory and a bunch of googling around hasn’t turned it up so pardon me if I get some details wrong.
https://www.independent.co.uk/news/people/obituary-capt-will...
It's an incredible story and deserves to be told. 1500miles at sea in an overloaded open lifeboat using stellar navigation and managed to save more than half of the people aboard. So they were sailing rather than rowing but other than that I had remembered it substantially correctly.