[OSM-newbies] aerial imagery vs OSM data - which is correct?

[John Werner]

John F. Eldredge <jon at feldredge.com> wrote:
>... both car and cell-phone GPS is that it seems to be more accurate
>when I am moving than when I am standing still.  

Many GPS units use something called "pinning" so that when you are stopped, your GPS coordinates will still show as stopped.  Without pinning, it is perfectly normal to see the coordinates reported by a stationary GPS change slightly ("jitter").

One typical algorithm used for pinning is to look at both the reported speed and position.  If the speed reported is high enough, the newly calculated position is reported.  If the speed is too low (typically < ~5kph), newly calculated positions are not reported until they show a nominal movement (several meters).

Pinning may work well for things that move quickly, but it can cause some interesting problems with it when doing activities like hiking, walking, and Geocaching.


- John 
-- 
John Werner
  http://www.snowtire.info
  http://www.frontiernet.net/~werner/