GPS Mapping Issues

Mapping software uses GPS information to determine your location based on measurements of your signal. This signal is used by mapping software to show tracks and movement on your devices.

Some common problems (others rare) that can affect the ability of any device to obtain good positioning data include:

• When a GPS is turned on or if the GPS has been inactive in the background for too long, the GPS needs to download data from the satellites that describes the position and timing of all of the satellites in the system. This can take up to five or more minutes to be corrected and can cause incorrect GPS tracking.
• Not enough satellites. Many GPS devices ideally need to receive signals from at least 7 or 8 satellites to calculate location to within about 10 meters. With fewer satellites the amount of uncertainty and inaccuracy increases. With less than 4 satellites, many GPS receivers struggle to produce accurate location estimates and will report “GPS signal lost” at points during the route.
• Poor hardware. If your device is older or does not have good GPS reception capabilities, it will struggle to receive satellite or cellphone tower signals.
• Low battery on GPS devices. A low battery can affect the proper functioning of the GPS on any device.
• Multipath signals. When signals from the GPS satellites or cellphone towers bounce off buildings, the GPS receiver can be confused by the extra time the signal took to reach it. In these cases, you may observe sudden errors in position. There is not much that can be done in these circumstances to reduce the effects of multipath errors. GPS is simply less accurate in these situations.
• GPS Drift. The GPS track deviates from the road. You may see that the route generally follows the shape of the road but with much less precision.
• Lost GPS signal. If a signal is lost and sometime later re-acquired, the pre- and post-signal-loss points will be treated just like any other two points (although more time has elapsed between them) and connect them with a straight line.
• GPS bounce. A ‘jumpy’ GPS track can cause your activity to report more distance than you actually travelled since each ‘zig’ and ‘zag’ of your GPS track has to be accounted for with a straight line connecting them.

• Radio interference or jamming. Satellite maintenance/maneuvers creating temporary gaps in coverage. In some cases, a device’s GPS hardware is working fine, but the software being used is faulty. For example, users can be misled with GPS software services including:

  
  
• Incorrectly drawn maps.
• Mislabeled businesses and other points of interest.
• Missing roads, buildings, communities, etc.
• Incorrectly estimated street addresses.