Re: [Paparazzi-devel] AGL and NavSetGroundReferenceHere()

[Martin P]

Hi, thanks for answering!

What I call AGL: What is displayed in the GCS. 
SRTM: I have a file N47E011.hgt.bz2.  
I am at N47.82 and E16.88. Does this file cover my location? 
If yes, I would say it is available. 
If no, where do I get it from? I did a "Google Maps fill". Btw, the terrain 
here is dead level.  

Greetings, Martin 

-------- Original-Nachricht --------
> Datum: Sun, 09 Aug 2009 17:07:54 +0200
> Von: Pascal Brisset <address@hidden>
> An: address@hidden
> Betreff: Re: [Paparazzi-devel] AGL and NavSetGroundReferenceHere()

> Hi,
> 
> what do you call AGL ?
>  - in the airborne code, NavSetGroundReferenceHere() sets ground_alt to 
> the current altitude (common_nav.c:84).
> This variable is for example use in HOME mode (nav.c:370) or in the 
> Takeoff and Final block of the basic.xml flight plan.
>  - in the GCS, AGL is computed by subtracting the terrain altitude (from 
> the SRTM model ... if the file is available in data/SRTM) from the 
> current altitude
> 
> --Pascal
> 
> Martin P wrote:
> > I use a flight plan with goround_alt=0 (derived from basic.xml).
> > After calling NavSetGroundReferenceHere(), I would expect that the AGL
> is 0. 
> > Instead, it is the altitude above sea level. The GPS mode is 3D and the
> AGL varies within 3 or 4 meters. 
> >
> > Is this the way it should be? Should I set the ground_alt to the actual
> altitude? 
> >
> >
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> >   
> 
> 
> 
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