[Openstreetmap] Inner city accuracy

Erik Johansson erjohan at gmail.com
Thu Jan 26 07:46:13 GMT 2006


On 1/26/06, Lars Aronsson <lars at aronsson.se> wrote:
> Three wheels that clamp on to a lamp post and can climb towards
> its top, carrying a GPS unit, a WLAN access point, and battery.
> Applied to a lamp post at a central street corner, the unit is
> allowed to climb up and the GPS receiver is programmed to average
> its position for a few minutes.  Then it broadcasts DGPS

> How difficult would this be to achieve?  What would it cost?  Is
> it realistic?  Has anybody done it already?

I'm unsure about this, it's an advanced subject.

The thing is, as far as I know the problem usually isn't in the errors
you can correct with DGPS. When satellite view is bad you will get a
bad fix, and there is nothing you can do about it. But if you have a
good view of satelites you could, with access to the raw GPS data
streams, increase your accuracy to 2cm. Since our GPS:es are some what
like black boxes you have no idea what kind of magic goes on in there
to get us a good fix.

To be able to do the calculations on DGPS you need to know what
satellites you are looked on to and the errors of those satellites. 
So you can't just take the x/y diff and get a better value.



/Erik




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