Precise take off

[Enhanced]

Hi guys and girls, hope someone can help it’s doing my head in.

Drone is a phantom 4 pro

For the life of me I cannot workout how or why it’s happening, when I go to take off, I click the little box for precision take off and hoover, the screen says it’s suppose to be 1.2 meters, everytime the drone takes off and flys to 5.8 or 6 metres and hovers, it’s done it since I’ve owned it.
I’ve completed all the updates, done compass and imu calibrations, the drone doesn’t seem to have any problems at all. Nothing is reporting a problem. Everything works fine.


What am I missing or have I done something wrong, I did notice before, I picked up the drone from ground height the VPS was changing but the height wasn’t changing. When it takes off the height seems to be right.

 

[crash1sttime]

Hi guys and girls, hope someone can help it’s doing my head in.

Drone is a phantom 4 pro

For the life of me I cannot workout how or why it’s happening, when I go to take off, I click the little box for precision take off and hoover, the screen says it’s suppose to be 1.2 meters, everytime the drone takes off and flys to 5.8 or 6 metres and hovers, it’s done it since I’ve owned it.
I’ve completed all the updates, done compass and imu calibrations, the drone doesn’t seem to have any problems at all. Nothing is reporting a problem. Everything works fine.


What am I missing or have I done something wrong, I did notice before, I picked up the drone from ground height the VPS was changing but the height wasn’t changing. When it takes off the height seems to be right.

The Mavic Pro when using Precision landing takes off and stops at 21feet, this is is that the camera can get a good view of the ground, im guessing the P4P is the same, why the app shows a different height maybe a bug in the app.

the VPS measures the height until 9ft or so then leaves it to the GPS to determine height

 

[dirkclod]

My Mavic don't stop at 21' but I take off manually but do wait for it to say to and hits back right.
Made a screen record of it and would think they are the same as crash said.

 

[Meta4]

the VPS measures the height until 9ft or so then leaves it to the GPS to determine height

DJI drones don't use GPS for altitude measurement.
They use a barometric sensor.

 

[PhantomFandom]

That is precisely how Precision Takeoff is supposed to work on a P4P. The 1 meter height is only for a non-precision automatic takeoff. If it only went to 1 meter, it would not have a wide enough field of view to properly get its precision landing view. The manual states that the craft must climb above 7 meters in order to properly set up its precision landing view.

 

[crash1sttime]

DJI drones don't use GPS for altitude measurement.
They use a barometric sensor.

Pretty sure I read that the newer quads use GPS for height, the old P2 used a barometric sensor. But then I googled it and found it I was wrong, you live and learn

 

[solentlife]

Pretty sure I read that the newer quads use GPS for height, the old P2 used a barometric sensor. But then I googled it and found it I was wrong, you live and learn

Risking the wrath of the 'gods' ....

It is not true to say GPS is not used for atitude at all ... but the main item used is Barometric pressure. It is more accurate.

GPS is used in our machines like most other GPS units in what is termed 3D mode. That is exactly what it means - 3D. If it drops to 2D mode which is 3 or less Sats - then it downgrades positional data .... GPS uses height above an ellipsoid that approximates the earth's surface. It cannot and does not account for topographical or geographical features. This makes it in terms of height evaluation too dangerous for our use.
IF it was used - then you would have a number other than zero for altitude at your home point.

Barometric pressure is based on a constant pressure change as you change height, for the range we are flying in - there is very little variation in that rate.
From sea level the pressure decreases with altitude at 27 ft/hPa, rising to 30 ft/hPa at 4,000 ft (1,220 m) and 40 ft/hPa at 15,000 ft (4,570 m). It is normal to assume 30 ft/hPa for our use.
At home point - it would basically declare the pressure detected as zero reference height. A drop in pressure then indicates increase in altitude ... an increase in pressure then indicates a reduction in altitude and in fact in the event of flying lower than take of home point - can display a negative altitude.

DJI gear uses Barometric as its primary height determination.