Taking off from roof of parking garage

[Tshred57]

Is it best (or even advisable) to hand launch from the roof of a parking garage? In certain urban areas those are the best places to keep LOS and get good shots. Anyone have success with this method?

This past week I tried taking off from the roof of a parking garage, got an IMU error, decided to fly anyway - using Lichti. The Mavic completed the mission but kept flying after the mission should have completed. The AC was maybe 700' away and I couldn't see it, but looking at the video on my phone either the gimbal was freaking out or the AC was doing flips. ATTI mode, perhaps. I did a RTH, which worked and it landed within inches of the takeoff point, somehow. I'd like to avoid white knuckles in the future but sometimes a park is just not available.

 

[Qoncussion]

Parking garages are loaded with rebar throughout the concrete. This is something to avoid. I would think that hand launching wouldn't make a huge difference, as you are still surrounded by steel - all around you. Just my .02. I'm sure others will chime in with some success stories, and how they got around the interference issues.

 

[Flawless]

I would avoid it - often, they have large amounts of ferrous metal in their structure like beams and reinforced concrete. As Qoncussion said; even if you handlaunch over your head at a distance of 2m, you're still surrounded by metal.

This will affect your compasses on takeoff - maybe not enough to prevent takeoff or cause a catastrophic error when you try and yaw (if compasses and IMU don't agree, they will cause serious issues when you yaw) but enough to cause other issues in flight. If your compasses are off, RTH may not function correctly either.

Be aware that if you power on your drone near metal, and then launch further away, it will still affect your compasses.

 

[Tshred57]

Thanks, guys. Rebar everywhere, metal railings, cars. I read someone suggest hand launching in another forum, but it sounds like I need to scout out a park instead. Not gonna try that again!

 

[4wd]

It shouldn't have caused an IMU error but compass issue is likely.
Hand launch would help, a compass error should go away once a few feet in the air but obviously it's not ideal.
The worst thing you could do is try to calibrate in the bad location because it says there's an error.

 

[Tshred57]

Yeah it's funny and a bit unexpected in that situation but sure enough, it read IMU error. And man was it squirrelly at the end of the flight. I calibrated the IMU that evening, launched from a park and flew the same "mission" the next morning, and things went great. I may still try the hand launch if I really have to. Could've been the IMU was just in need of calibrating. No compass error readings that I noticed. Litchi logs go to Airdata and I couldn't find much insight looking at those.

 

[4wd]

A lot of concrete surfaces are likely to contain rebar, the roof of a building like that might be no worse especially if there's anything you might use which is up off the ground a bit - low wall or similar.

 

[Tshred57]

I found a nice park - right next to US Circuit Court, City Hall, Municipal Court, the Police Department and the FAA offices, in case I'd be needed at any of those fine places, lol. It'd be perfect except, well, you know... I'll look for another park and if not found, the parking garage I'm looking at looks to be older, perhaps with concrete walls. I agree that would *probably* do the trick. It'll cost 10 bucks to find out. The one I was at last week had all metal barriers - everywhere. I think with a compass error once you launch you should be okay? At least, I've done that before and it was fine (too close to my car - that may have been magnetic interference come to think of it). The IMU was miscalibrated - 3 of 4 were green, one was orange.