Issue with altitude

[Amatea]

First, sorry for my english. I hope you will understand my issue.


I have an issue with my H Pro.
The last time I flew I realized the update from the 1st of September and I did a compass calibration and everything was ok.
This afternoon I flew with the update of the 1st of september. Not the last.
Before flying, I did an accelerometer calibration. And on my flight site a compass calibration.
And I have an issue. I take off on a flat field. The altitude is ok.

But after there is an issue with altitude indicated on my ST16.
Beacause quickly it’s a sloping field. So when I fly horizontally normally the altitude must increase because it’s a slope.

But on the ST16 the altitude doesn’t change.
If I go down in altitude in the sloping field, the altitude on ST16 become negative because I am lower than my take-off point.
So the altitude is not correct.
And after nothing is good.

I'm not sure that the accelerometer calibration is ok. During the procedure I have the blinking and beep and green light. But the lights of H don’t stop at the end of the accelerometer calibration.

I try many times to recalibrate the compass and the accelerometer. And the last firmware. But still the same problem.

 

[BobW55]

Your H uses a barometric sensor for altitude. When you take off it thinks the take off point is ZERO (meters or feet) above ground level.
If you fly DOWN a hill it will indicate negative altitude. This is normal.

 

[Rayray]

Are you having other problems?
Is your RealSense working if you turn it on?

 

[Amatea]

Your H uses a barometric sensor for altitude. When you take off it thinks the take off point is ZERO (meters or feet) above ground level.
If you fly DOWN a hill it will indicate negative altitude. This is normal.

Thanks. But it's normal if after when I land to my "zero point" the altitude is wrong.
For example, instead of 0 meter: 4 meters...

 

[Amatea]

Are you having other problems?
Is your RealSense working if you turn it on?

Never used it for the moment.

 

[Tuna]

Drones do not know where the ground is, so altitude is always relative to the start point. The barometric altitude can also drift, so even landing back at the same point can show a small difference from zero,

 

[BobW55]

It is not 100% accurate.
If there was a change in pressure between the time you took off and landed it will be off.
It uses the pressure sensor more to hold altitude when you release the he control sticks.
Fly when a weather front is moving through your area it will be way off.

 

[Amatea]

It is not 100% accurate.
If there was a change in pressure between the time you took off and landed it will be off.
It uses the pressure sensor more to hold altitude when you release the he control sticks.
Fly when a weather front is moving through your area it will be way off.

I understand now.
It is normal...

 

[Rayray]

4 meters on the ground at the starting point? I don't know. it's normal for the ST-16 to indicate the wrong height, say -3 or -4'. (1 meter?)
When the H first starts, it usually tries to zero the altitude. But I see it varies after that, may be off 10' or so in the air, and may say several feet when it comes back and touches down in the same spot. If you have no other problems there may not be anything wrong.

With the legs raised, can you lower it below 5' or 6' (2 meters?) The IPS on bottom should stop it until you let the legs down. Not connected to the ST-16 height reading.

Bob, does this still sound fairly normal to you?

 

[Amatea]

4 meters on the ground at the starting point? I don't know. it's normal for the ST-16 to indicate the wrong height, say -3 or -4'. (1 meter?)
When the H first starts, it usually tries to zero the altitude. But I see it varies after that, may be off 10' or so in the air, and may say several feet when it comes back and touches down in the same spot. If you have no other problems there may not be anything wrong.

With the legs raised, can you lower it below 5' or 6' (2 meters?) The IPS on bottom should stop it until you let the legs down. Not connected to the ST-16 height reading.

Bob, does this still sound fairly normal to you?

I didn't try to lower it below 2 meters.
I will try it tomorrow.

For the moment I fly only on angle mode. Without Realsense. And everything is ok...

Thinking about that, the weather today was not very good.
Windy, cloudy with, ray of sunshine, and wet.

 

[BobW55]

Even an altimeter in an airplane is probably +-5 feet accurate.
Now the airliners use radar altimeters, very accurate.
I would not rely on the altitude readout on the ST-16 to be accurate at all. Have seen mine jump all over. May NOT say zero on take off but it is usually stabilized to a near zero reading.

 

[prathbun]

So, here's why we need to allow plenty of extra altitude for CCC flights; especially if, like me, you do a lot of flying over trees.

I'm not posting this to prove a point or to ***** at Yuneec (I know that the components in these critters are what they are, and I'm overall very happy with my TH), I was just curious how much temperature does or doesn't affect the baro.

The H had been in my truck overnight — got down to around 13°F — and I brought it inside for this test. I assume that the internal temp had risen a few degrees before I put in a (room-temperature) battery. I took off the props, booted it up and just let it sit on the floor of my 70° office for a while.

As you can see, over a 3-hour period the barometer varied by as much as 11 meters. Even after warming up (at around 1:30) it varied over 10 meters. The +/- 2 meters between :37 & :40 is OK, but the rest is pretty non-trivial. The error's especially bad (steep) when you start with a cold bird...

When I fly in cold weather (the only flying I've been able to do since getting my H early this month), after 10-15 minutes in the air I regularly see 20 to 30 feet on the altitude readout when I'm about 6 feet above my takeoff point.

 

[PatR]

Thanks. But it's normal if after when I land to my "zero point" the altitude is wrong.
For example, instead of 0 meter: 4 meters...

If the temperature surrounding the barometer has changed since the time of take off the altitude will change as well. Temperature affects density, which establish pressure. Expect this to happen since electronics generate heat.

The standard altitude lapse rate is 3*/1000' of elevation change. It requires very little temperature change to impact an altitude reading with a cheap baro sensor. Impacting all that further, the temperature sensor in the H is terribly inaccurate.

 

[PatR]

Even an altimeter in an airplane is probably +-5 feet accurate.
Now the airliners use radar altimeters, very accurate.
I would not rely on the altitude readout on the ST-16 to be accurate at all. Have seen mine jump all over. May NOT say zero on take off but it is usually stabilized to a near zero reading.

Bob,

The FAA legal allowance for altitude error with an altimeter on an IFR certified aircraft is 75'. The IFR standard is more demanding that VFR requirements. If our little toys are only off 5-10-20-30-60' off they are doing better than legally required for a tougher flight environment than they are allowed to use.

Not at all related but something for people to have some fun with. The only time a commercial aircraft fuel gauge has to be accurate is when it reads 0/Empty.