How does the GPS calculate the exact distance to my destination on a curvy road? I understand how a straight road works, but not a curvy road. And how is it so exact, like down to 100ft? Does it involve a calculus-like approach where you take incredibly small measurements from a satellite and add them up?
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Curved roads would just be distance traveled like any other road. For example when you drive 1 mile, it doesn’t matter if the road is straight or curved 1 mile is 1 mile. Your ending position will be different, as will the straight distance from your start to end position, depending on the shape of the road…but you still only traveled 1 mile.
GPS itself though doesn’t know anything about length of a road, that’s the job of the map makers who create mapping software that leverage your position from the GPS device.
How exactly it measures length of roads depends on how the software is coded. It may be automated to detect roads based on satellite images and use a known scale of the image (this often comes from the imaging software), or someone may know the length of a road and manually program that into the software (usually into a database used by the software), or even a combination of both where the process is automated, and then refined manually.
Once you have the length of all the roads plugged in you can create a route from point A to point B. The mapping software can poll the GPS device to find your exact location, overlay that onto the map to know where on the map you are, then it can just calculate the distance from where you are (point A) to where you are going (point B) because it already knows the length of all the roads.
**tl;dr** – Methods may vary depending on the software developer, but the mapping software – not the GPS system itself – does this measurement. GPS only provides location information.
Does the length of a piece of string change if you curve it? No, simply the end and/or beginning is in a different 3D space. The same is true for roads.
GPS does not give you distances. GPS only gives you position from satellite signals. it’s up to the navigation app/device to calculate distance.
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