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Altitude Above Ground Level

TXBidean

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It appears that the altitude reading in the Go4 app is the altitude above/below the launch point. If I am correct, is there a way to set it to above ground level (AGL) from the drone’s immediate location? I know that this is probably just wishful thinking as the Mavic 2 doesn’t have ground facing radar. Or radar of any type for that matter.
 
You are correct, it does not know where the ground is until you get close to ground when out buzzing around. That would be a useful feature though. Some third party apps have the ability to estimate this, but that is using online data that is not always accurate.
 
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That is not even a functional web site.
That is nolimitdronez.com

But nothing what they do give GO4 the ability to have the aircrafts altitude AGL displayed. (at its immediate location)
 
This won't help with manual control flight but I believe Litchi, and perhaps some other apps that are used to set up and save missions, can automatically calculate AGL for waypoints when used with Google Earth.
I've seen a tutorial on this but can't recall the title. I'll take a look and post a link if I find it.
 
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That is nolimitdronez.com

But nothing what they do give GO4 the ability to have the aircrafts altitude AGL displayed. (at its immediate location)
it does show on screen true altitude above ground
 
DJI GAVE YOU GPS AND GLONASS, NOW NLD GIVES YOU EUS GALILEO TOO! NEW NLD GO 4.1.22 INSTRUCTIONS FOR GOOGLE MAPS:
New NLD GO 4.1.22 instructions for AGL height over changing terrain:
Tuesday, July 10, 2018
0001120_350.png

To enable displaying of AGL height over changing terrain, for this function to work correctly for NLD GO 4.1.22 - you will need to do a couple of things:
  1. Go to Earthdata Login and sign up for an account
  2. Go to 30-Meter SRTM Elevation Data Downloader and download up to 4 "tiles" for your flying area and save them to your device you use with GO
  3. Install NLD GO 4.1.22. You will need to copy these "tiles" to a your device in the DJI\srtm_data folder. Leave them zipped, so they would look like N21W172.SRTMGL1.hgt.zip and so on.
  4. Copy and paste the names of these files into a .json file installed on your device. (Due to the different data sets, we can't do this for your area) Go to DJI\og_settings and edit the dtm.settings.json file. This will be easier to do on your PC. Open this file with the editor of your choice, or you can use Notepad. It will look like this:
{"m_AlgoChoice":3,"m_AlgoParams":[30.0,5.0,15.0,3.0,50.0,20.0,3500.0],"m_AltitudeOffset":0.0,"m_DTM_tiles_paths":["/mnt/sdcard/DJI/srtm_data/N21W158.SRTMGL1.hgt.zip","/mnt/sdcard/DJI/srtm_data /N21W159.SRTMGL1.hgt.zip"],"m_DoLogging":false}
  1. Replace the names of the files currently in RED with the names of your files (“tiles”). Only replace the names of the two that are there and leave the rest of the text alone. So for my example, I will only have one to replace, so the result after editing will be:
{"m_AlgoChoice":3,"m_AlgoParams":[30.0,5.0,15.0,3.0,50.0,20.0,3500.0],"m_AltitudeOffset":0.0,"m_DTM_tiles_paths":["/mnt/sdcard/DJI/srtm_data/N21W172.SRTMGL1.hgt.zip"],"m_DoLogging":false}
  1. Save your changes and transfer back to your device, replacing the one that is currently there. (DJI\og_settings\dtm_settings.json) Keep a backup of the original. All you want to do is replace N21W158.SRTMGL1.hgt.zip and or N21W159.SRTMGL1.hgt.zip with the name of your tiles for your area. Make changes to this file as you fly in different areas that need different tiles. Check the map here: http://dwtkns.com/srtm30m/ You can have up to 4 tiles listed at a time in this file.

Galileo satellite support built into this version of GO will be implemented soon!! (in the mean time, this would be all you do to get it working, once we turn it on)
Install NLD GO 4.1.22. Allow NLD GO to have a data connection for a short while before or at the field with your bird connected. This allows the sat info to be downloaded quicker into GO and transferred to your bird. You only need to do this once for the initial download. Thats it! Enjoy!
`Quad808 and the rest of the NLD crew
 
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it does show on screen true altitude above ground
It does show the altitude above the launch point.

If you are flying in the the direction of an elevated terrain, it still shows the altitude above the take off point, whereas the aircraft is flying closer to the ground direct beneath it.
 
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True.

That's why i am currently working on the integration of a device capable of realtime AGL measurements for commercial UAV based on a laser ranging device Jenoptik - LDS 30 with DJI Matrice series.
 
Looks like vaporware. Even if it does what it says you are relying on 3rd party data that you have downloaded. Not real-time.

Vaporware or not, a digital elevation model on the aircraft and/or mobile device is the only reasonable approach to monitoring altitude AGL on consumer-level drones when not close to the ground.
 
Just strap a laser range finder on the aircraft. $100
How are you going to 'merge' the ranger finders output (height/distance to GND) into GO4?
 
Just strap a laser range finder on the aircraft. $100

Apart from adding a 200 g payload, that's not going to work unless the aircraft is level. And how is it going to deal with vegetation? Lidar systems are much more than simple rangefinders.
 
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