Additional indoor navigation aids, be it for DJI or other?

[Lady Rover]

Hi,

we just declined a lucrative contract for flying inside. It would have required to fly a lot and very close to walls.
Due to sketchy GPS and numerous (up to 100ft) height levels inside optical sensor navigation would also have been difficult.
ATTI mode was considered unsafe by us, because of the drift issue due to propwash and wall proximity.

Now here is the question. Are there some other methods to aid a drone when flying inside by putting up some sort of optical or radio beacon system inside?
Are they commercially available?
What kind of prices are we looking at?

I'm asking generally and not necessarily only geared towards DJI, even though a method to add an additional receiver to, say, a Mavic would be fab.

I could see a system based on a Wii or similar.

Keen to learn from your know how, thanks,

Fran

 

[GerdS]

Have you already considered using a cine whoop instead of a usual drone?
They are perfect for indoor flying and don't need any assistance except for good piloting capabilities. Risk for damage of drone, persons or interior is minimal.

 

[Keule]

Are there some other methods to aid a drone when flying inside by putting up some sort of optical or radio beacon system inside?
Are they commercially available?

You can use multiple GNSS repeaters in the area you intend to fly.
Depending on the chosen type you can have cm level accuracy (RTK equipped aircraft reqd.)

Yes, it is commercially available. I have used a similar setup for inspections inside tanks.

Price: Not cheap - Visit this website GPS Repeaters - Aucon and give them a call.

 

[Lady Rover]

Hey, had to look up what a CineWhoop is

Essentially it's a small ducted fan quad drone.
At least from a crash perspective that's better. Still in our case we would have had to fly 100ft high with an additional horizontal blower attached to the drone.
The purpose was not filming or photography in our case.
We would have had the need to fly consistently about 2ft from the walls. So some sort of reliable navigation would have been needed.

For filming the CineWhoop looks great!

 

[GerdS]

You can use multiple GNSS repeaters in the area you intend to fly.

Sorry but this will not work!
GNSS repeaters just broadcast the satellite constellation seen at the location of their own receiving antennas, so all receivers who rely on the repeater will all see the same position, even if they are e.g. 10m away. Not applicable for indoor navigation!

For the task of blowing onto walls from a defined distance I don't see an out of the box solution based on drones. A special flight controller would be required which relies on distance measurement to the wall.

 

[Keule]

Sorry but this will not work!
GNSS repeaters just broadcast the satellite constellation seen at the location of their own receiving antennas, so all receivers who rely on the repeater will all see the same position, even if they are e.g. 10m away. Not applicable for indoor navigation!

That's why I wrote:

You can use multiple GNSS repeaters in the area you intend to fly.

You need more than one repeater. 4 minimum (in each corner of the building ...) Then each external GNSS antenna repeats its position to the inside ...

 

[Lady Rover]

Thank you.

That's actually what would have been needed, but it's out of our price range :-(

Guess neither it would work with a Mavic or similar, no?
Perhaps more like a custom built drone with an Ardupilot controller?

I do understand how it works though. Four GPS receivers with known position. Then the drone communicates with these 4 receivers to calculate its position fix in relation to them. Clever.

You can use multiple GNSS repeaters in the area you intend to fly.
Depending on the chosen type you can have cm level accuracy (RTK equipped aircraft reqd.)

Yes, it is commercially available. I have used a similar setup for inspections inside tanks.

Price: Not cheap - Visit this website GPS Repeaters - Aucon and give them a call.

 

[Keule]

Guess neither it would work with a Mavic or similar, no?

It'll work with any GNSS system. If it is a Mavic or any other GNSS receiver.

 

[GerdS]

That's why I wrote:

You can use multiple GNSS repeaters in the area you intend to fly.

You need more than one repeater. 4 minimum (in each corner of the building ...) Then each external GNSS antenna repeats its position to the inside ...

Even this would not work. Satellite navigation systems work by measuring runtime differences for signals from different satellites. A receiver would only use the signals of just one repeater in time. So if its position will get changed (due to a drifting drone) it would not recognize this until it comes into the range of the next repeater. There it will see a jump in position and that will result in an out of control drone.

 

[Keule]

Even this would not work. Satellite navigation systems work by measuring runtime differences for signals from different satellites. A receiver would only use the signals of just one repeater in time. So if its position will get changed (due to a drifting drone) it would not recognize this until it comes into the range of the next repeater. There it will see a jump in position and that will result in an out of control drone.

Indoor Positioning Based on GPS:

http://research.sabanciuniv.edu/27141/1/gpsmotl.pdf

 

[Lady Rover]

Hmm. Keule says he did actually use such a system to fly inside tanks. So, I guess it does work?

The drone would need to be able to receive all 4 transmitters at the same time.
Don't forget, normal GPS receivers get their fix from many satellites in parallel by measuring the runtime of the signals.

Even this would not work. Satellite navigation systems work by measuring runtime differences for signals from different satellites. A receiver would only use the signals of just one repeater in time. So if its position will get changed (due to a drifting drone) it would not recognize this until it comes into the range of the next repeater. There it will see a jump in position and that will result in an out of control drone.

 

[Lady Rover]

But how is ensured that the Mavic only communicates with the beacons and does not get confused if it picks up an outside GPS signal occasionally?

I think I might give those guys a ring and see how much it would cost to rent the beacons for 3days...

It'll work with any GNSS system. If it is a Mavic or any other GNSS receiver.

 

[GerdS]

Indoor Positioning Based on GPS:

http://research.sabanciuniv.edu/27141/1/gpsmotl.pdf

You should read that more accurately. It works only with modified GPS receiver algorithms, not with the standard ones.

 

[Lady Rover]

Are there any systems using optical or infrared beacons? Might be cheaper?

 

[Keule]

You should read that more accurately. It works only with modified GPS receiver algorithms, not with the standard ones.

I think I was just lucky as it worked perfectly with an old M100.

 

[Lady Rover]

Which means in turn a special drone, à hacked drone or a drone using an open software like Ardupilot.

You should read that more accurately. It works only with modified GPS receiver algorithms, not with the standard ones.

 

[Lady Rover]

Actually, thinking about it I do think it would work with a normal drone.
The 4 repeaters basically behave like 4 additional satellites for the drone.

So it most likely is also not an issue if she picks up also outside signals once in a while.

Interesting stuff!

I think I was just lucky as it worked perfectly with an old M100.

 

[Lady Rover]

OK.

I talked to the Aucon guys. It's not that simple.
You need to add roof antennas exactly on the same location above the beacons, and the beacons are too expensive even if for rent (=they are normally not available for hire).

All in all way more expensive than what our project would have created in revenue.

He said also a wifi based positioning system might be another thing to look into.

 

[Lady Rover]

Drone indoor navigation – DIY Drones

 

[GerdS]

If I would need something like you need, I would indeed think about adapting ArduCopter for this task. I would not use any GPS but just tracking technics. Not in direction to the floor as usual, but directed to the wall instead. So I could use an ultrasonic or laser based sensor for holding constant distance from the wall and in case the wall has some optical recognisable structure also for holding position. The big advantage would be that no infrastructure is required which makes it much more cheap for your customers.
This is no easy (and for sure not a cheap) solution you can just buy somewhere but a custom development. It would also be a nice task for a masters thesis at an univerity. Perhaps you can contact a professor there and propose this for his students, so you might get a working prototype.