while hovering and idling for a bit above ground level I noticed how off the altimeter reading was at about 3 feet the altimeter showed 25 or so - how does the altimeter get calibrated ? If I do an accelerometer reset prior to flying it seems to be ok until one powers off to perform a battery change. Anybody else having this issue ?
Altimeter reading way off
- Thread starter AZSteveB
- Start date
The Barometer controls that.
The reading should, even briefly, zero when you spin up the props prior to takeoff. BUT, if the area barometric pressure is changing, up or down, the sensor converts that into plus or minus height. Annoying to land with an indicated height of 20', lol.
Pay no mind to that, it's function to to set the maximum height, like 400' or whatever, where 10 or 20 feet don't make much difference.
So as long as the reading zeros when the props spin up, you're good to go.
The reading should, even briefly, zero when you spin up the props prior to takeoff. BUT, if the area barometric pressure is changing, up or down, the sensor converts that into plus or minus height. Annoying to land with an indicated height of 20', lol.
Pay no mind to that, it's function to to set the maximum height, like 400' or whatever, where 10 or 20 feet don't make much difference.
So as long as the reading zeros when the props spin up, you're good to go.
Yeah wasn't sure if the reading was providing landing info back to the sonar sensors or not if it had been it would certainly have been way off ! I'll have to watch for the zeroing to happen at startupThe Barometer controls that.
The reading should, even briefly, zero when you spin up the props prior to takeoff. BUT, if the area barometric pressure is changing, up or down, the sensor converts that into plus or minus height. Annoying to land with an indicated height of 20', lol.
Pay no mind to that, it's function to to set the maximum height, like 400' or whatever, where 10 or 20 feet don't make much difference.
So as long as the reading zeros when the props spin up, you're good to go.
Unacceptable. My APM and Pixhawk are within a few feet. I don't believe it's the barometer interested the telemetry. The flight controller users the barometer to maintain altitude, if the barometer was that far off, the aircraft would be bobbing up and down like a yo-yo. Accurate attitude in one of the most important information needed.The Barometer controls that.
The reading should, even briefly, zero when you spin up the props prior to takeoff. BUT, if the area barometric pressure is changing, up or down, the sensor converts that into plus or minus height. Annoying to land with an indicated height of 20', lol.
Pay no mind to that, it's function to to set the maximum height, like 400' or whatever, where 10 or 20 feet don't make much difference.
So as long as the reading zeros when the props spin up, you're good to go.
PatR
Premium Pilot
Sonar and optical sensors function off of reflected energy. There is no numerical altitude data interaction between Real Sense, OA, and IPS. The altimeters used for consumer level multirotors are not accurate. Do not depend on them for anything more than casual reference.
The drift usually happens fairly slowly, and pilots automatically correct during flight. If you've ever done fast runs close to the ground you'll be familiar with the drone dropping a little as the barometer adjusts to the different pressure. The only exception is if you're in built up areas, where wind speed around buildings can cause local changes in pressure that cause 'sudden' drops.
If you sit any drone so that it's purely relying on barometric pressure (ie you're out of the range of ground sensors), then you'll see the same drift. Over a ten minute flight, it's quite possible to be out by 20'. Normally though you'd never notice it as you don't leave the drone holding position for long periods. There are YouTube videos comparing various drones' ability to 'sit still' - and they all move up and down over time.
The other thing that can affect readings is change in the temperature of the drone. If you've brought it out from an air-conditioned house to a hot sunny garden, then the barometer will drift even further as it warms up.
PatR
Premium Pilot
Tuna,
APM based systems are typically quite accurate in altitude and position holds. Altitude is well maintained during high speed runs if the power system was set up correctly.
APM based systems are typically quite accurate in altitude and position holds. Altitude is well maintained during high speed runs if the power system was set up correctly.
What PatR said. Next week I will do some testing as to what I think the problem is. I have been meaning to do this but have not remembered. The way the barometer is mounted and baffled I think is the problem. We had similar problems with APM back in the days, it should be an easy fix.
If you let you H hover when it is somewhat windy, you will see it drop a few feet and then recover. That is due to pressure changes. As the wind blows across the body of the H it create a negative pressure. The flight controller thinks it is going up then drops the H. When the pressure comes back up after the wind gust the flight controller regains prior altitude. This tells me there is nothing wrong with the barometer it self. There is either a problem with baffling or the telemetry software is not converting properly or accurately.
If you let you H hover when it is somewhat windy, you will see it drop a few feet and then recover. That is due to pressure changes. As the wind blows across the body of the H it create a negative pressure. The flight controller thinks it is going up then drops the H. When the pressure comes back up after the wind gust the flight controller regains prior altitude. This tells me there is nothing wrong with the barometer it self. There is either a problem with baffling or the telemetry software is not converting properly or accurately.
I'm not disagreeing with any of that. We all know that the barometer changes reading constantly. I don't think it's a baffling issue as the value would recover when the Typhoon returned to a holding position.
The thing to remember is that the flight controller compensates - it tries not to adjust too quickly and to smooth out variations. So though the drone moves up and down with pressure changes, it is trying to limit the range of movement. It looses track of 'zero' as it tries to maintain that level flight. The conversion is consistent and the telemetry reflects the work that the flight controller is doing to try to overcome the limitations of barometric height measurements.
As Pat says, it's not the end of the world - the altitude measurement is not critical to flight, particularly as the Typhoon should be in VLOS at all times.
The thing to remember is that the flight controller compensates - it tries not to adjust too quickly and to smooth out variations. So though the drone moves up and down with pressure changes, it is trying to limit the range of movement. It looses track of 'zero' as it tries to maintain that level flight. The conversion is consistent and the telemetry reflects the work that the flight controller is doing to try to overcome the limitations of barometric height measurements.
As Pat says, it's not the end of the world - the altitude measurement is not critical to flight, particularly as the Typhoon should be in VLOS at all times.
PatR
Premium Pilot
Your last paragraph is the saving grace for the Typhoon altimeter. If people are operating the H within the boundaries of the law the altitude displayed is not a critical item because they can see how high it is relative to other objects. For those concerned about RTH heights it's a simple matter to add 50' or so to allow for altitude errors. This is a non issue even for people that allow a lot of tall trees and such to come between them and their H. All they have to do is assess their path of intended flight beforehand and adjust RTH height accordingly. Some might ask how do I know this. The answer is pretty simple to figure out.
I agree with Charlie, the fix is likely very simple.
I agree with Charlie, the fix is likely very simple.
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