Re: [Paparazzi-devel] Re: Differential GPS through Paparazzi

[David Buzz Carlson]

DGPS is _normally_ done with another receiver at a known GPS location.  
This receiver then computes the difference between what it received at a 
certain time and what the actual location is.  It then sends that data 
to the airborne unit.  Because of this, there is a slight lag in when 
the data is received and when it can actually be used by the airborne 
platform.  I'm not sure if that lag would prevent you from using it how 
you propose, but it would definitely be an interesting project.

Buzz

James Maday wrote:
> Hello Marcus-
>
> Having purchased to sets of the TWOG bundle, my first idea would be to 
> use the second bundle's GPS attached to either our landing net or the 
> GCS for differentiation with the aircraft's GPS.  If we attach the 
> second GPS to the landing net, we could get really accurate landings I 
> think. 
>
> If necessary we would purchase a different GPS receiver, but hopefully 
> we don't need to.  I guess the question you asked me, Marcus, is one I 
> should pose to readers as I'm unable to definitely answer it myself: 
> what sort of secondary GPS receiver is needed to run a DGPS system 
> with Paparazzi?  How would the two GPS coordinates be manipulated in 
> the software to more accurately obtain altitude?
>
> Thank you for reading and responding,
>
> -James Maday
> Saint Louis, MO, USA
>
> >Hello James,
> >
> >what would be the source for the differential signal?
> >Do you suppose to get it throught the uplink from
> >the GCS, some kind of local receiver on the AP or
> >some kind of network-device on the AP?
> >
> >Marcus
>
>
> On Tue, 17 Mar 2009 00:54:09 -0500, James Maday <address@hidden 
> <mailto:address@hidden>> wrote:
> >> Hello Paparazzi fans-
> >>
> >> I'm working with a team developing a UAV which will very soon 
> employ the
> >> Paparazzi Autopilot (AP) for navigation.  We have only just begun
> >> programming our airframe.xml, but before we get far I'm hoping to 
> answer
> >> this feasibility question: is differential GPS (DGPS) usable by the
> >> Paprazzi
> >> system for altitude measurement?
> >>
> >> I've searched the mailing list and didn't find any previous talk of 
> using
> >> DGPS with Paparazzi, so I figured I'd poll the audience to see if 
> anyone
> >> has
> >> tried and can offer advice.  Thank you very much!
> >>
> >> To answer my question here are some basic project details.  The UAV 
> must
> >> maintain 10-15 feet (roughly 3 - 4.5m) above the ground following
> >> predetermined waypoints for 10 hours.  We have two sets of the TWOG 
> with
> >> LEA_5H GPS device from PPZUAV.  We are using a laptop w/ Intrepid 
> Ubuntu
> >> Linux for the GCS.  An example of a UAV that uses DGPS in its AP is the
> >> ScanEagle by Insitu/Boeing.  (
> >> http://defense-update.com/products/s/scaneagle.htm )
> >>
> >> -James Maday
> >> St. Louis, MO
> >>
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>
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