Hi,

I was wondering if anybody has any experience about that.
What I would like to do is to fly inside a metal span bridge, which looks similar to this one:
http://www.dziennik.com/images/m ... idge_773_460_80.jpg
but it's a pedestrian bridge with very limited traffic.  So, basically is a tunnel-shaped metal cage.
The drone would be around 6 feet above the floor of the bridge and could easily land at any time in case of a problem. I would use tripod mode and narrow sensing for a better precision.

When I try to take off from the bridge obviously I am getting a compass error, but I was wondering if taking off from an area next to the bridge and flying into it would work.
I just need 1-2 mins of footage when the drone would be moving inside a tunnel-like structure, so we are talking about 100 feet long path inside the bridge, about 6 feet from any of its structural elements. There are about 13-15 satellites visible at that location, so GPS would work, but the compass may not.

Any suggestions? Is it worth trying?

PS. I've been flying indoor before in tripod mode and with narrow sensing enabled and it worked really good, so was hoping to do them same with this bridge.

Thanks!

If you have a chance trying it first with taking off from the bridge I would do that.
Or at least switch on the drone and see if you get warnings.

If that is not an option and you are taking off near by - why not.
I would also fly tripod mode and downward positioning system on.
If you get compass errors and the drone starts acting funny, be ready to switch immerdiately into Atti!
For that matter you want to have some confidence with flying in Atti - and it shouldn't be windy!

In any case you want to make sure not to get into a situation where the drone goes into RTH.
It's gonna hit for sure one of the stanchions while ascending.
Unless your distance to the drone is less than 20m. Mabye you can follow it by foot? Then it goes down where it is.

Good Luck!

Set RTH to hover. Practice ATTI just in case.

I wouldn't try taking off from the bridge there is to much metal and could cause erratic behavior.

Thanks!
Yeah, I tried and I can't take off from the bridge, but there is a parking lot just next to its entrance, so I should be able to take off from there.
Setting RTH to "Hover" makes a lot of sense, because the drone shouldn't get any higher than 10 feet, otherwise, it will hit some of the metal structures. Very low wind in case it will switch to ATTI also seems to be very good idea. I can definitely follow the drone on foot, so if it pretends to land I will be just a few feet away.

I think I am going to try and will let you know how it worked, but first need to wait for a very calm day

piowoc73 Posted at 2017-5-15 13:51
Thanks!
Yeah, I tried and I can't take off from the bridge, but there is a parking lot just next to its entrance, so I should be able to take off from there.
Setting RTH to "Hover" makes a lot of sense, because the drone shouldn't get any higher than 10 feet, otherwise, it will hit some of the metal structures. Very low wind in case it will switch to ATTI also seems to be very good idea. I can definitely follow the drone on foot, so if it pretends to land I will be just a few feet away.

Like what was already mentioned, taking off from a nearby location should allow for you to do what you want. Again, you really want to take extreme precaution when performing in an area that is known to cause interference.

piowoc73 Posted at 2017-5-15 13:51
Thanks!
Yeah, I tried and I can't take off from the bridge, but there is a parking lot just next to its entrance, so I should be able to take off from there.
Setting RTH to "Hover" makes a lot of sense, because the drone shouldn't get any higher than 10 feet, otherwise, it will hit some of the metal structures. Very low wind in case it will switch to ATTI also seems to be very good idea. I can definitely follow the drone on foot, so if it pretends to land I will be just a few feet away.

If it is cast iron rather than steel then there may be no problem since cast iron probably does not significantly affect the earths magnetic field.

However, even if it is cast iron, since there is likely to be a lot of modern steel bolted to it I suggest you fly in Atti mode only while inside the structure, too much risk of disaster in GPS mode and it quite likely wont fly straight anyway!

And be ready to cancel any low battery RTH.

Do not calibrate the compass anywhere near the bridge.

I did it this morning and it went surprisingly good. The main trick was to take off just a few feet from the bridge and then to fly into it using tripod mode and narrow sensing.
I was really surprised that the drone didn't even show compass error. The only warnings I got were from obstacle avoidance, even with the narrow sensing constantly on. What I realized was that the drone wasn't as stable as it normally is in tripod mode, sometimes acting a bit erratically, but it was within reasonable limits.
Although I am not sure how useful the footage will be because I had to keep my eyes on the aircraft all the time, so didn't actually see what I was filming, but I hope for the best. I am downloading the footage now and will be checking it shortly.

Thank you guys for your help!

piowoc73 Posted at 2017-5-16 08:17
I did it this morning and it went surprisingly good. The main trick was to take off just a few feet from the bridge and then to fly into it using tripod mode and narrow sensing.
I was really surprised that the drone didn't even show compass error. The only warnings I got were from obstacle avoidance, even with the narrow sensing constantly on. What I realized was that the drone wasn't as stable as it normally is in tripod mode, sometimes acting a bit erratically, but it was within reasonable limits.
Although I am not sure how useful the footage will be because I had to keep my eyes on the aircraft all the time, so didn't actually see what I was filming, but I hope for the best. I am downloading the footage now and will be checking it shortly.

Good to hear it worked out.

I am glad too. The footage turned out to be totally usable.

DJI-Jamie Posted at 2017-5-16 11:01
Good to hear it worked out.

Jamie, I know it's off topic, but let me ask you, as you seem to be a very helpful person: is DJI planning on releasing GS Pro for other platforms than iPad?  I would be very interested in trying it on an Android device.
Thanks

piowoc73 Posted at 2017-5-16 11:50
Jamie, I know it's off topic, but let me ask you, as you seem to be a very helpful person: is DJI planning on releasing GS Pro for other platforms than iPad?  I would be very interested in trying it on an Android device.
Thanks

It's something that being looked into but there isn't an ETA at this time.

ok, so what u would want to do if this was a p3, u'd want to set your RTH altitude low, disable Smart Return Home, change settings to "hover" or "throttle down"  on signal loss. Now that you know the rth altitude, take off from somewhere where flying the bridge will be at that altitude - this way in the unlikely even it does RTH, it will NOT ascend and hit the top of the bridge above it... So take off, fly and walk to your destination - then be ready to flip to ATTI mode in any sign of trouble.. You could consider filming 60 or more frames, as available, and fly through fast, then slow it down when editing the video....
That is all I can think of for now...
As noted above, P4 is a bit different story and so on.
Glad it worked out. When u gonna share the video?