Altitude when changing terrain heights.

[Meta4]

GPS information is three dimensional so the P3 will get information with VNAV (vertical navigation). Of course the barometer is much more sensitive so will be the primary altitude sensor.

GPS may give information for altitude .. but the Phantom ignores it and only takes altitude info from the barometer which is much more accurate.
Test any handheld GPS. You can be at sea level and it will tell you that you are 80 feet below and then a few minutes later, 30 feet above.
You don't want your Phantom paying any attention to that sort of data.

 

[Bret Lucas]

GPS may give information for altitude .. but the Phantom ignores it and only takes altitude info from the barometer which is much more accurate.
Test any handheld GPS. You can be at sea level and it will tell you that you are 80 feet below and then a few minutes later, 30 feet above.
You don't want your Phantom paying any attention to that sort of data.

VNAV DGPS data is better these days. Look it up

 

[MHaerialphoto]

Appreciate all the technical info.
More thoughts. It does use it's barometer, it just choose to make the datum the takeoff point. So, it has no frame of reference to when the ground below it changes, other than the sonar/camera on the bottom, which is only useful to how many feet?

 

[Foosy]

GPS information is three dimensional so the P3 will get information with VNAV (vertical navigation). Of course the barometer is much more sensitive so will be the primary altitude sensor.

GPS navigation may be 3 dimensional but relative to a perfect sphere. GPS does not know. Where the mountains or valleys are. Hence cannot be used for altitude, just for relative altitude.

 

[Meta4]

VNAV DGPS data is better these days. Look it up

I looked it up .. it's expensive and probably not small enough for a P3.
Our Phantoms don't have VNAV DGPS and they ignore the altitude component of their GPS because its accuracy is quite poor.