I might add that so far, all the righteous indignation over the altitude limit has done very little to stifle DJI's staggering market penetration.
Demonstration of why Altitude Limits should be removed
- Thread starter The Roach
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- over 400 feet
I might add that so far, all the righteous indignation over the altitude limit has done very little to stifle DJI's staggering market penetration.
That's because they make very competent and inexpensive equipment. With the current issues over the use of DJI by government agencies I've been looking at the market for alternatives, primarily to the M210 but also at the lower end of the range. As far as I can see they have no realistic competitors across that entire range, either in capability or price.
What about using the US map MSL database for elevation? Litchi has access to that in their mission hub. Google does too in their Google Earth app. As long as you have access to that data, I would think it's a simply math calculation to get a relatively accurate AGL estimate when in a hover almost anywhere. I think if Litchi wanted to, they could implement their woman's voice to announce AGL estimates on a regular basis, or when prompted. Wouldn't that be the bees knees?
This data should allow easy AGL calculation to be fairly accurate (within 50', maybe 25') in the app, for very little money, no extra weight, I would think.
1. Access to MSL map elevation data via internet, via cellular.
2. Known MSL elevation from take off point, based on the internet MSL data.
3. Known GPS map location (horizontal) of the craft on a quasi real-time basis, as received by the craft today.
4. Known present relative elevation from take-off point, based on barometer measurements from take off point, as calculated today.
Put all the data together from the above 4 sources and I think you could calculate AGL most anywhere on the map, again...... only IF you have an internet connection.
Lastly, even though GPS elevation isn't accurate, granted, sometimes up to 100' off, vertically, this is better than nothing IMO. It takes a lot of experience to estimate AGL elevation based on the view in my iPad. In some cases, such as hilly or mountain terrain, I would appreciate a GPS estimate from time to time, knowing well it's not very accurate, because it's better than nothing. But again, GPS MSL elevation data, as inaccurate as it is, doesn't do any good without #1 above to calculate AGL, based on map location.
And for those that think the barometer is accurate, it's NOT! I've had my Phantom4 come back after a 10min flight to my cliff launch site, where the VPS sensors are 100' above the ground, and the craft is even with my head, just 30' away from the cliff I took off from. GO would show the craft is 50' high (relative to take-off point), when it should say 6' ! So the barometer isn't very accurate either. Others have reported this anomaly also.
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I can't believe I'm reading this from a former pilot. Altimeters are set to barometric pressure, not zero. This gives you an altitude readout above sea level.
On the contrary, barometric altitude is more accurate than GPS altitude. All aircraft use barometric altimeters as primary altitude reference which is above sea level. Radar altimeters measure above ground level but many aircraft do not have these.
N017RW
Premium Pilot
GPS does not "measure" altitude.That is a calculated value. Barometers, only measure atmospheric pressure to "approximate" altitude which can be quite a variable. Atmospheric pressure is not "exact" at any given altitude depending on conditions. Radar altimeters, are still a bit bulky and pricey and are really more than needed for the hobby world, but are extremely accurate to terrain and altitude.
The variables of atmospheric pressure are not a factor when all aircraft set their altimeters to the SAME local pressure reading. The atmospheric pressure may change with distance but all aircraft attitudes will change with this pressure plain if they set their altimeters to the same local barometric pressure setting. At 18,000 feet and higher, all aircraft set their altimeters to 29.92. This is the universal pressure plain. As long as every pilot does this (required by law) all aircraft will be on the same atmospheric pressure plain regardless of changing barometric pressure. Obviously as one travels the barometric pressure changes. Referring to altitudes below 18,000 feet it is necessary for pilots to update the barometric pressure in his/her altimeter with pressures measured at their present location or altimeter readouts will become progressively inaccurate with distance.
I'll end this discussion here as it's leaning heavily towards fixed wing operations. It would be nice if radar altimetry was affordable for our drone world but for now, we'll have to live with our limitations.
Safe flying!
I'll end this discussion here as it's leaning heavily towards fixed wing operations. It would be nice if radar altimetry was affordable for our drone world but for now, we'll have to live with our limitations.
Safe flying!
With a network connection giving access to something like the Google maps DEM then it would certainly be possible for the app to estimate altitude AGL. The problem offline is that the dataset is too large.
It would not necessarily require an accurate MSL altitude to start with either - it could just assume that the launch is from ground level and track subsequent vertical motion with the barometric sensor. The problem with GPS MSL altitude is not relative inaccuracy (see my graphs above) so much as that it is not actually relative to MSL - it's relative to a reference geoid from which MSL can deviate by a significant amount.
The problems that I can foresee are that the DEM does not take account of vegetation (i.e. trees) or buildings which may be tall compared to the altitudes that we fly at. If alttude AGL were displayed I suspect that people would try to rely on it and end up outside VLOS crashing into trees and structures, and then blame DJI.
Alternatively, it could simply be used to raise and lower the maximum altitude dynamically without displaying altitude - that might be a better option.
On your observation of barometer errors - that maybe unavoidable around cliffs due to updrafts, which will reduce the local pressure away from the cliff face and fool the FC into calculating a higher altitude than expected.
I agree with the above. Just to clarify, my reference to barometric accuracy was from what I know about airplanes. They have what's called "sensitive altimeters". You are correct referring to the inaccuracies of barometric measuring in consumer drones.
Actually the sensors in the drones are pretty good. Even an expensive pressure altimeter in an aircraft is going to be fooled by sudden, local, pressure changes where the airmass flows around large structures - if that is what happened in the case reported. It's a real pressure change. It would be interesting to see the DAT file from one of those flights to compare the GPS altitude data with the barometric altitude data when the Phantom flew into that region.
Apple DOES kowtow yo Chinese interests. They recently banned all VPN apps in the Chinese App Store because the Chinese government prohibited them. They had to to continue doing business in that country.
In the beginning there were no rules. For everyone did as they should and problems were few. Then the first trouble maker came along and did a bad thing, and thus the first rule. And then everyone started searching for a way around the first rule, and from there were all the other rules born.
That's what I used to tell my employees when I was a manager.
My concern is with so many so called pilots out there that sooner or later something really bad might happen, and then the FAA is going to be a real problem, not just a nuisance. Getting my license ASAP boys, for what it's worth. And the unlicensed guys who don't have a clue will be the downfall of many of us.
That's what I used to tell my employees when I was a manager.
My concern is with so many so called pilots out there that sooner or later something really bad might happen, and then the FAA is going to be a real problem, not just a nuisance. Getting my license ASAP boys, for what it's worth. And the unlicensed guys who don't have a clue will be the downfall of many of us.
This is no different than today. If you plow into a tree and the Go4 elevation says 75', the pilot is clearly liable. I see no personal responsibility changing from a calculated AGL versus an ALP (above launch point) elevation. The pilot is always responsible for know their flight system telemetry and where they fly.
This is such a simple concept, I'm sure DJI will provide this kind of calculated AGL estimate at some point. It's clearly doable, without the extra weight of a "laser range finder", and it's certainly better than nothing, which is what we have today.
It's certainly true that the responsibility is on the pilot, but I'm sure the complaints will come anyway. If that isn't perceived as a concern by DJI then I'm sure that you are correct - it will happen, either when the onboard memory becomes sufficient to include a sufficiently high-resolution global DEM or, as you suggested, when a network connection is available.
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Newbie Q. How does the drone keep track of it's changing altitude AGL? if it can't, how does it limit you to 400' AGL when flying towards downhill terrain. wouldn't it have to tie GPS to an accurate map database with terrain altitudes? or does it have a radar altimeter I don't know about? I'm getting a headache.
