Urban GPS

This figure shows two GPS tracks in central London, collected with an Android cell phone.

The left image shows crossing a bridge and walking along the river, and shows a generally very linerar and realistic path, especially considering that some of the paths go under the bridges.  Exceptions are two random points on the north side of the bridge.

The image on the right shows the path in the dense urban canyons, where high buildings block much of the view of the sky.  Signals from the GPS satellites travel complex paths with multiple reflections, adding the path length and leading to incorrect trilaterations with positions that are only approximately correct.

These results will vary with the quality of the GPS; these used a Nexus phone.
 

Last revision 12/10/2017