[Paparazzi-devel] Re: Flight plan altitude data.

[Helge Walle]

Thanks a lot, Thomas !

I followed your advice, and this works just fine in Paparazzi.

I compared the elevation data to places in my area with known height above sea level, and they are good to within a few meters from my local maps and also to what the gps says.

These data also made me understand how AGL works.

Still I would be interested in some understanding of the <while cond="LessThan(NavBlockTime(), 10)"/> statement, if anyone could enlighten this.

Thanks,
Helge.





Helge,

looks like original data from USGS doesn't cover your area. 
But you can download http://www.viewfinderpanoramas.org/dem3/P31v2.zip
- unzip P31v2.zip, cd P3, bzip2 *,mv * $PAPAHOMEDIR/data/srtm and try
again.
Good luck.

Regards,
Thomas



Am 16.06.2010 23:07, schrieb Helge Walle:

 

Hi,

 

I live at   lat0=60.381221   lon0=5.152867 in Norway. I can not find any SRTM data for the area where I live.

 

I am working to understand the altitude data in the flight plan, and also the "AGL" value in the GCS. I have searched through the mailing list for explanations; found some, but still I have a way to go.

 

The following is part of my current flight plan:

<block name="Geo init">
<while cond="LessThan(NavBlockTime(), 10)"/>
<call fun="NavSetGroundReferenceHere()"/>
<call fun="NavSetWaypointHere(WP_HOME)"/>
<set value="ground_alt" var="waypoints[WP_TD].a"/>
<set value="ground_alt+10" var="waypoints[WP_AF].a"/>
</block>

Questions:
Does the statement <while cond="LessThan(NavBlockTime(), 10)"/> specify the time of determining "ground_alt" ?
How is this statement explained ?
How is "AGL" in the GCS computed? Is it the altitude given by the GPS minus "ground_alt" ?
Is "Alt" in the GCS the altitude given by the GPS at any time ?

Thank you for any help,

Best regards,
Helge Walle.