Eli5 how does the GPS know exactly how Long it will take you to get somewhere? Factoring in driving at different speeds or unforseen traffic that’s an hour away
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The navigation unit uses it’s maps to calculate a route. The maps have speed limit data for the roads. The programmers will put in an average speed for each road type (which would have been calculated from real world driving data). A bit of time will be added to account for stopping at junctions etc.
Standing alone navigation units won’t account for unforseen traffic unless they have a way of getting traffic data. If there is traffic data available that will give an indication of how long the delay is which can then be factored in.
If you’re talking about Google maps, or other big GPS systems, they have lots of people everywhere using the system, which means lots of real time data of how long its taking people to drive from one place to another. So they know about the “unforseen” traffic that’s an hour away. They assume you are going the average speed of traffic, so the prediction might be too short or too long if you manage to outdrive everyone else, or if you drive like an old lady.
It doesn’t know exactly, it estimates based on all the data the app can get.
Like how long it took others, your average driving speed, traffic news, and so on.
It knows how fast on average people drive on each road on the route. Not all GPS systems have ways to calculate traffic though. Google uses crowdsourced data from its users and some systems can pull in data from a centralized database like a city’s DOT that tracks traffic conditions.
This is why the estimate will change if you drive slower/faster than average or if you run into unforseen traffic
It doesn’t. Try writing down or memorising the ETA it gives you at the start, and see if it’s always accurate to the minute. It won’t be. It can use current and historical traffic data to predict what traffic might be like by the time you get further into your journey, but of course it can’t know things like if there’ll be a crash or not, whether you’ll sneak through that annoying light that sits on red for ages or get stuck behind a tractor for five minutes on a narrow road with no overtaking possibilities, whatever.
It measures the distance along the roads to the destination. I knows the speed limit. Time = distance / speed. That’s the travel time if there’s no traffic. But it knows if there is traffic because there are other people driving over there, and it can track how fast they’re all going because they have phones on GPS too. So if the cars on this one mile of road are going 20 mph instead of the 30 mph speed limit, it estimates you’re gonna go 20 mph there also, so the travel time is slower.
A “simple” GPS device like a Garmin has a map built in, with speed limits also attached to each stretch of road. So when you plug in a destination, the GPS analyzes the roads between you and your destination, and is able to calculate the time the various possible routes will take by basically dividing speed from distance.
When it comes to a “smart” GPS device like a phone running Google Maps… Google is collecting data from everybody’s phone, and it’s able to use this data to determine where there are traffic jams, and to adjust your ETA accordingly. (Famously, someone created a fake traffic jam by borrowing a hundred smartphones and wheeling them around on foot in a little red wagon.)
Years ago Google bought Waze. That service tracked all it’s users and told you about traffic. Now Google puts that in maps. Even if you don’t have maps running Google knows where you are and how fast you are going. It takes all that data and puts it together to give other users a picture of traffic.
Looks like you got answers to the question.
But, I’m going to point out that GPS, the “Global Positioning System/Satellite(?)”, knows nothing about the roads, traffic, historical travel times, direction of travel, origins, destinations, nothing. It *only* knows (approximately) where you currently are.
ALL of the rest regarding navigation and travel times is dealt with by software on your device or a server to which your device is connected.
When a GPS accounts for traffic, it’s monitoring the speed of other users who are currently driving on that road. Even if traffic is moving, the system will still track how fast drivers are going, but I think most systems have an upper limit of the speed limit.
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