[OSM-newbies] difference between yahoo WMS and gps track

[James Ewen]

On Fri, Feb 5, 2010 at 7:16 AM, Jonas Stein <news at jonasstein.de> wrote:

> The track shows in JOSM as a very smooth line. Walking on one other side
> of the street back shows a parallel dotted line like . and '
> Then i draw a way in the middle the WMS pendant is shifted
> 10 to 30 metres but has same shape.

The WMS photos may not be rectified against the real world properly.
In my area there's about a 5 metre shift. You can adjust the
background image location in Potlatch so that it lines up with
reality.

The general rule is to trust the GPS. Our GPS accuracy is very good,
much better than the olden days when SA was enabled. Every generation
of GPS coming out just gets better.

My GPS navigator has a feature where it will lock me to the road
database, rather than believe the GPS location. This would have been
good back in SA times, but now I complain bitterly because the road
database errors drag me away from where the GPS engine says I am, and
I know that the GPS engine is more accurate than the road database in
the navigator is a number of places.

James
VE6SRV