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mbe

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Hi,

Just wanted to ask the following question: would it be feasable to spoof the GPS TX stream on a Mavic Air 2 to get around the limitations? The idea is the following: install a small arduino (nano or Rasp. pico); the TX line from the GPS would go to a nano, and nano would also output the TX data back to the rest of the circuit.

Nano would read the incoming stream; it would apply a certain factor (2-4) to the altitude, i.e. for each additional 2-4 meters of real height above take-off point, it would add just one meter.

I wonder of there are any catches with this idea?

Possible issues:

- I assume that the GPS modules used in Mavic use standard plain ASC messages (no secure communication).
- Not sure if they may have a verification with barometric pressure, i.e. how DJI system would interpret a different altitude from GPS/pressure.
- I looked at the cable harness, it is pretty complicated to get physically; probably the best would be to open the GPS cover to get to the TX line and cut it there.
- the voltage levels probably is 3 V so a pico would be a better option.

Any thoughts about this idea?
 
The following two freeware programs allow drone users to achieve more, ahem, flexibility with their drone flying missions. Consider these free and easy options before embarking on any surgical procedures or software tinkering.

DankDroneDownloader.com and DumlDoreV3.

Should you prefer to pay for such products, you cannot go wrong with No Limit Drones, or Drone Hacks.com, both of which will set you back a modest 40 euros per drone license. Note that you will need to use those freeware products even if you go with the payware versions. The reason for this will become apparent should you choose to go this route, as opposed to the complex DIY procedure you described above.
 
Thanks for the tip, I would look into it. I have read though that Mavic Air 2 is not changeable. The idea behind my hardware hack is that it would be foolproof, futureproof and applicable to any drone, i.e. the only way for the manufacturer stopping it from happening is to use additional sensors to verify GPS validity (barometric or inertial) or to use closed communication protocol from GPS to main board. Also, it occurred to me that ground radio control may have a GPS, not sure about that...

In terms of programming, it is very straightforward, and not only would you be able to modify the altitude but also position, which would eliminate issues like no-fly zones and transmitter power settings; the take-off point would always be somewhere in the Pacific...

The main technical problem is to make three connections - power, ground and TX line which would have to be cut...
 
Hi,

Just wanted to ask the following question: would it be feasable to spoof the GPS TX stream on a Mavic Air 2 to get around the limitations? The idea is the following: install a small arduino (nano or Rasp. pico); the TX line from the GPS would go to a nano, and nano would also output the TX data back to the rest of the circuit.

Nano would read the incoming stream; it would apply a certain factor (2-4) to the altitude, i.e. for each additional 2-4 meters of real height above take-off point, it would add just one meter.

I wonder of there are any catches with this idea?

Possible issues:

- I assume that the GPS modules used in Mavic use standard plain ASC messages (no secure communication).
- Not sure if they may have a verification with barometric pressure, i.e. how DJI system would interpret a different altitude from GPS/pressure.
- I looked at the cable harness, it is pretty complicated to get physically; probably the best would be to open the GPS cover to get to the TX line and cut it there.
- the voltage levels probably is 3 V so a pico would be a better option.

Any thoughts about this idea?
Good idea!

However the limitations for the altitude is fused between imu and barometric. No gps at all.

For avoiding restricted flightzones I think it's possible.

On tha mavic 2 it was a simple tx/rx 3v. I bought a tracker that listens on the rx and sends beacon on a vhf freq in case of flyaway with tah last updated lat/lon.
You might even use the same hardware as this ding :)
 
Well, that is a pity... I did not know that the baro is the main source... spoofing barometric sensor is much more complicated. For one desoldering it is pretty much a precision job, and for other, emulating the sensor is much more complicated. I do not know which chip they use, but most precision chips use complicated correction factors and formulae, and emulating them is not straightforward at all... plus they use high speed interface and usually have several communication options, either SPI or I2C, so that reverse engineering is not so easy.

I would doubt that IMU would be used for large scale altitude measurements; they would be good for hovering, but the error would accumulate, so that it is very unlikely the 500 meters are enforced through IMU.

My idea was exactly to circumvent the altitude issue...
 
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