[gps-talkusers] 300 feet off 33 okay
- From: Michael May <mikemay@xxxxxxxxxxxxxxxx>
- To: gps-talkusers@xxxxxxxxxxxxx
- Date: Thu, 15 Mar 2007 14:41:03 -0700
To summarize this discussion, there are at least 3 factors that go into
accuracy or shall we say inaccuracy considerations.
1. Map data error. I believe the Tele Atlas spec is something like 12 meters
accuracy but I am sure this varies depending upon how they obtained the data.
One can learn about the street data quality by checking the distance to the
intersection when standing at it or by asking for a pedestrian route and then
noting where the waypoints are set and how they trigger when you come close to
them. As mentioned, if a user records a point, the GPS accuracy when that point
was recorded calculates against the error when playing that point back. Those
errors could cancel each other out or they could add together.
2. GPS signals: The quoted average is 30 feet. We all know that GPS accuracy
ranges from 10 feet to 100 feet or more.
3. Distance to the center of the intersection: As Chris points out, the center
of the intersection is where the two mid lines cross from the intersecting
streets. In astreet with 2 lanes each way, this distance could be50 feet.
A reminder that there is a document called GPS Accuracy contained in the
documents folder that comes with the Sendero GPS or within the documents zip
file on our download site. There is lots of good things to learn in this
document about accuracy factors.
Mike
At 08:14 PM 3/14/2007, you wrote:
>Hello:
>
>Many thanks for the responses. But I am still confused. I am not near a
>military base. The problem is not limited to street addresses, but to
>intersections as well.
>It is just odd that I can be an intersection, standing a few steps from the
>corner and the GPS tells me that I am 180 feet from the corner. THE same time
>the GPS tells me that I have good reception.
>Thank you again.
>
>JD
Other related posts: