[Openstreetmap] Inner city accuracy

[Lars Aronsson]

Christian van den Bosch wrote:

> I gather Galileo won't hit showtime till 2008 at least, so I 
> wouldn't hold my breath on that front. WAAS is slowly becoming 
> more available, both in terms of regions, and units that support 
> it. DGPS has been somewhat revived by DGPS-over-IP, but I don't 
> think it'll ever really be mainstream.

While I was walking around some streets today, I thought up the 
following guerilla mapping device:

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 
(differential GPS) signals over WLAN, which operates in the 
license free 2.4 GHz band.  In your backpack, moving around the 
nearby streets, you have another GPS receiver and WLAN receiver 
than uses both the direct GPS signal and the differential.  You 
could even have a directional WLAN antenna that you point towards 
the station in the lamp post, for 100 meter range.

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


-- 
  Lars Aronsson (lars at aronsson.se)
  Aronsson Datateknik - http://aronsson.se