Tom,
Your results are not unusual. A newer handheld navigation-grade
receiver has an accuracy of 3 to 5 meters at best (older ones without
WAAS have an accuracy of 10 m). Slowly changing (over hours)
atmospheric effects can introduce an systematic offset into your
coordinates of 3 to 5 or even 10 meters.
And as others have pointed out, the positional [in]accuracy of Bing and
Canvec could exceed 10 meters.
Best Regards,
Brent Fraser
On 11/19/2012 8:29 AM, Tom Taylor wrote:
I will do a resurvey in the way you suggest. It was really
disappointing to find I couldn't trust my GPS at all (well, I did some
mental adjustment of waypoints to place building entrances), and being
off by a constant amount for 4 km certainly makes one suspicious.
A bit to the north, my GPS survey of some footpaths behind a school
matched Bing nicely. It would be really interesting to find some sort
of disconnect in between.
Je manquais de la courtoisie envers les francophones qui suivent cette
liste. En sommaire, j'ai tracé une piste de longueur totale environ 4
km, mais l'a trouvé toujours environ 10 metres à l'ouest des entités
déja presents sur la carte et les images Bing. Je vais faire un autre
sondage pour mieux comprendre la situation.
Tom Taylor
On 19/11/2012 8:37 AM, Connors, Bernie (SNB) wrote:
Tom,
The transmission lines would not affect your GPS accuracy. I agree
with Pierre that you could repeat the track and see if the two tracks
are similar. Another thing you could do is identify several
identifiable points in the Bing Imagery such as the intersection of
two sidewalks, the corner of a sports field, etc. Go to those points
and use your GPS to record a waypoint and use position averaging with
about 3 minutes of recording to get a more accurate location and then
compare those waypoints to the Bing imagery. Position the Bing
imagery so they match up with your waypoints and then look at your
GPS tracks top see how they line up with the Bing Imagery.
Bernie. -- Bernie Connors, P.Eng Land Information Infrastructure
Unit, SNB [email protected]
...
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