### HDOP values

Where I live is reasonably hilly so often I get a HDOP which is higher than the default (Which is around 2m I beleive) Im generally getting 3.5m or so.

Ive looked but cant find where I can increase the min HDOP value. so

1) Is there a parameter to change somewhere and

2) what would absolute safe min be? Im thinking between 3-4m.

Its usually whilst still on ground. Once up 20m signal improves, so it generally happily finds its way home, then I guide it to the ground if needed.

I currently have to disable the full preflight check (as it wont let me just set ignore GPS for some reason,keeps reverting to ignore throttle?) to let me arm.

Cheers

-P

#### Replies

• This is a great suggestion. Ideal geometry is one SV at zenith (directly overhead) and at least 3 SVs at about 45 degrees of elevation from the horizon spaced 120 degrees apart in the sky. For a 3D fix, you need at least 4 SVs in view of the receiver/rover unit. Another problem might be the rover/receiver almanac. If the almanac is out of date, the receiver has no idea what SVs to expect, where they should be, or what their health is.

GPS signals HATE trees, buildings, mountains, and water. Trees reflect signals and prevent them from reaching the receiver.. Buildings, mountains, and water reflect them, but may allow the signal to arrive at the receiver late...or twice...causing multipath errors which often manifest in erratic spikes in elevation data. Clouds don't really have much effect on the signals.

To answer the question about DOP values, the highest I would allow in a resource-grade or survey-grade receiver is 6.0. DOP is a dimensionless number, meaning it is a statistical value with no units of measurement. The value of 6.0 represents APPROXIMATELY the 95% confidence interval for your positions. Obviously, you want these values to be as low as possible.

• I wouldnt call them mountains...jsut nearby hills.. But even they block it.

but move 10m toward the coast and its good..so must jsut be angle to satellites.

Maybe New Zealand isnt as covered as major countries too.

3-4 should be fine _. usually hitting 2.5-3.5 but I think by default it needs under 2 to get a green go light.

-P

• http://diydrones.com/group/arducopterusergroup/forum/topics/failure...

Change hdop value in parameters