Proof of location for online polls - Network Latency Geolocation
Information about a device's physical location can be inferred by measuring the time it takes for signals to travel between the device and a known server location.
As the speed of light cannot be exceeded according to the known laws of physics, a maximum possible distance can be established with certainty, based on the signal latency.
Multiple measurements to different servers establish circular areas of possible locations on the earth's surface which can then be intersected.
https://ip-vote.com/geolocation_via_latency.html
