How does google maps knows that there is a road over this place i mean we have roads all covered with dense trees so if they use satellite’s, the satellite’s hardly can see a road from top, so how do they figure out?
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Google has a lot of sources, but at some point they all come down to the fact that someone at some time actually made a note of where that road was. This could have been a survey, like the UK’s ordinance survey, or it could be municipal records, or it could be people driving along the road with a GPS device.
Google has to put a substantial amount of work into translating all those data sources into something their computers can use. If the data source is well structured, that might be automated. If not, then Google has hired someone to manually translate that information into a form they can use. This sometimes can include manually tracing the road from a satellite image.
You can participate in a version of this process yourself by the way. The OpenStreetMap project is always looking for volunteers to update their open source database of navigation data and maps.
They have a lot fewer sources available to them, since they need to work around copyright. Obviously they can’t just copy Google Maps. Even survey data might be restricted by copyright. But people can definitely contribute their own GPS data, as well as finding other sources to use.
[https://www.openstreetmap.org](https://www.openstreetmap.org)
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