Obviously Google Maps uses GPS, that's how it shows your location on the map. Whether it uses that to show your actual altitude, idk. A simple test would be to see what happens when you go up a tall building.
They laser map it from space.
Why would they do that when they can get the elevation dataset (created from a laser mapping satellite) that covers every square inch of the planet from the USGS/DMA)?
It uses a location derived from your IP address when you use a regular browser. It may, if available, use GPS on a handset to determine your location. However, the GPS elevation data is not very accurate on a handset (or even a dedicated garmin GPS receiver). To get accurate elevation data with GPS you need differential GPS which uses multiple receivers.
It's related so far as the rendered map is based on WGS84 and a particular latitude and longitude relates to a number of tiles (png's) depending on the zoom level.
Ultimately it relates to vector data that describes the road and is rendered to produce the map tiles. The Google cars are collecting photographic data but they are also collecting the GPS coordinates used to build or update the vector data.
The photographic material is geotagged so it can be related to the location. Mist smart phones and newer digital cameras do the same thing. The EXIF data embedded in the image contains the location where the photo was taken.
Paper maps tended to do a lot of guessing.
Since your location is determined using triangulating distance from multiple satellites, why would elevation be any less accurate than any other dimension?
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Though this condition is not exactly hard to fulfill with 31 functional GPS satellites orbiting the Earth right now, discrepancies crop up because the speed at which radio waves travel gets affected by the variations in the density of the ionosphere. The general rule of the thumb is that vertical error is three times the horizontal error. If a decent signal reception is available, a modern GPS receiver should be able to give elevation data accurate to a range of 10 to 20 meters (35 to 70 feet) post correction.
And that's exactly where the problem with GPS-based altimeter watches meant for the great outdoors lies. The GPS reception isn't always terrific and hikers have reportedly found the altitude measurements to be off by as much as 400 feet!
Garmin confirms this, explaining that the main source of error has to do with the arrangement of the satellite configurations during fix determinations.
"The earth blocks out satellites needed to get a good quality vertical measurement. Once the vertical datum is taken into account, the accuracy permitted by geometry considerations remains less than that of horizontal positions."
As such, the values provided by GPS-based altimeters should be used with caution when navigating.
Thaf area isnt flat at all, its quite hilly.
Google tends to use everything available so it is hard to believe they are not collecting GPS info from the cars.
They definitely do for traffic monitoring. That's how they know where the delays are, how it will slow you down and if an alternate route is better. They show you on the map yellow or red areas on the highways with slowdowns. Sometimes it works really well. Sometimes not, sadly. I was in NYC a few weeks ago on the lower east side. When I first activated it upon starting the car, it showed to go across into Brooklyn and then via Staten Island. But as I was exiting the garage, it had switched to using the Holland Tunnel, which is how I came in. So, I followed it. By the time I got over near the tunnel, the traffic was a total disaster, worst I've ever seen. A garbage trunk had gone off an overpass on the NJ side of the Lincoln Tunnel, that tunnel was shut down in both directions. And this was like 3PM, beginning rush hour and it was the day before 4th of July holiday.
I guess GM was only reacting to the traffic it saw, as it happened, ie there was no prediction, human or otherwise, based on the Lincoln being shutdown. For the Holland to be totally screwed was sure to happen. I sat in traffic at lights for maybe ten light cycles, without the traffic ahead of me moving at all. It took me 3 and a half hours to get home, usually at that time it would be ah nour and a half, maybe two if it's bad. If it had diverted me into Brooklyn and SI, I'm sure it would have been two hours tops.
This does not list "incorrect local terrain height" and also it is a manual process for correcting errors. There is no such thing as a feature in Google Maps that tracks your GPS position and reports it back to Google for inclusion in the maps. The road information comes from offcial (and their own) surveys, it is not like a road will be added to the map when one or more Google Maps users cross a field somewhere.
And similarly, the local terrain height is not influenced by the height indicated by users when they use Google Maps.
They even use sheep these days:
Including inside some malls and department stores. I forget where I saw that.
If the field happens to be a new development?
Better be careful who you let into your house!
Wow. That's good. They go slowly so the pictures won't be blurred.
How does GMaps get updates to street maps.
Does it infer the streets from computer analysing the sat view?
Or do municiplities send it updates when they construct new streets?
In some places, they show paths between houses with a dotted line? Who tells GMaps about the paths? If you choose Walking, it will route you over the path, but no other method of travel will go that way.
Part of the Kennet and Avon Canal towpath in England is on "strretview" , no street anywhere near
We all know google leans left so why would you be afraid to have a democrat from google inventory your house? Isn't socialism all about sharing?
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