Must launch from garage roof - suggestions?

sdunwell · Jul 6, 2020

A new project requires launching from a very large concrete garage roof, then flying up 300' and over 100' to show a building site and views. There is no other nearby launch point on the ground, and several nearby buildings add congestion. Any suggestions for safe ops, especially regarding the compass? Would it help to use a table-top on saw-horses, or on an aluminum ladder to get away from the rebar while powering up? Several cycles of power up - power down will be needed. Really hoping to NOT calibrate compass on site. Inspire 2 and also Mavic 2 Pro will be used. Thanks!

Starz · Jul 6, 2020

More info on what material the garage roof is made of would be useful.

sdunwell · Jul 6, 2020

Parking garage - concrete - typical - assuming full of rebar. 3 stories tall. Very few cars inside, and usually none on the roof at this time.

Starz · Jul 6, 2020

Could be an issue. The sawhorse idea would be worth a shot.

Dobmatt · Jul 6, 2020

sdunwell said:
A new project requires launching from a very large concrete garage roof, then flying up 300' and over 100' to show a building site and views. There is no other nearby launch point on the ground, and several nearby buildings add congestion. Any suggestions for safe ops, especially regarding the compass? Would it help to use a table-top on saw-horses, or on an aluminum ladder to get away from the rebar while powering up? Several cycles of power up - power down will be needed. Really hoping to NOT calibrate compass on site. Inspire 2 and also Mavic 2 Pro will be used. Thanks!

Precautions are very simple: rise the launching pad above concrete as high as you can, power the system and check compass reading bar. If it's on green and the system doesn't display any warnings, you're good to go! Avoid flying to close to a surrounding tall buildings as they may reduce satellite reception below required minimum count. Be prepared for sudden switch to ATTI Mode all the time. That's all.

Anyway, you never - I mean NEVER - calibrate compass on site just because the system reports compass problem!!! This is a suicidal decision. Go with the drone somewhere else and check compass reading there ...

sdunwell · Jul 6, 2020

This is very helpful. Thank you. I know there are lots of recommendations about when/where to calibrate the compass. Not in a field of metal, for sure.

mmarian · Jul 6, 2020

Dobmatt said:
Precautions are very simple: rise the launching pad above concrete as high as you can, power the system and check compass reading bar. If it's on green and the system doesn't display any warnings, you're good to go! Avoid flying to close to a surrounding tall buildings as they may reduce satellite reception below required minimum count. Be prepared for sudden switch to ATTI Mode all the time. That's all.

Anyway, you never - I mean NEVER - calibrate compass on site just because the system reports compass problem!!! This is a suicidal decision. Go with the drone somewhere else and check compass reading there ...

I get compass warning and amber light flashing quite frequently on various locations even if no apparent magnetic interference is around. I DO calibrate compass on locations, just making sure I follow the basic rules, no mobile phone in my pocket or car keys, no ferric metal object like park benches etc nearby. I never had any issue resulted from calibrating compass on location.
Launching from elevated platform about 1m above the concrete slab with rebar should do the trick and make I2 compass happy. Just do not calibrate the compass while standing on concrete slab with rebar but that would be stating obvious?.

Dobmatt · Jul 7, 2020

mmarian said:
I get compass warning and amber light flashing quite frequently on various locations even if no apparent magnetic interference is around. I DO calibrate compass on locations, just making sure I follow the basic rules, no mobile phone in my pocket or car keys, no ferric metal object like park benches etc nearby. I never had any issue resulted from calibrating compass on location.
Launching from elevated platform about 1m above the concrete slab with rebar should do the trick and make I2 compass happy. Just do not calibrate the compass while standing on concrete slab with rebar but that would be stating obvious?.

Marian, your statement about the need for frequent compass calibration supports my thesis (again and again) that - when it comes down to DJI drones - we never know what we gonna get. Of all 6 birds I've been able to collect by far (Phantom 3 Pro, Inspire 1 Pro, Phantom 4 Pro+, Inspire 2, Matrice 200 and Mavic 2 Pro) only Mavic is regularly demanding compass calibration as a precautionary maintenance. I'm traveling hundreds miles with Inspire, checking compass reading before every flight. No issue whatsoever...

mmarian · Jul 7, 2020

Dobmatt said:
Marian, your statement about the need for frequent compass calibration supports my thesis (again and again) that - when it comes down to DJI drones - we never know what we gonna get. Of all 6 birds I've been able to collect by far (Phantom 3 Pro, Inspire 1 Pro, Phantom 4 Pro+, Inspire 2, Matrice 200 and Mavic 2 Pro) only Mavic is regularly demanding compass calibration as a precautionary maintenance. I'm traveling hundreds miles with Inspire, checking compass reading before every flight. No issue whatsoever...

My Inspire 2 only started to request this frequent Compass Cal since the latest FW upgrade. But it is not a big deal for me really. Calibration only takes a few seconds to do and if it makes my Inspire happy I do not mind to do it whenever it askes for it. I have had zero real issues in all those 3 years I've owned it, so I have very little to complain about.

PhilZ · Jul 7, 2020

I have flown off the tops of both buildings and many parking ramps and have never had a compass warning.
I use a cheap (mostly plastic) card table from a discount department store to launch from. Never, ever (600+) flights, had a compass warning.
Good luck.

sdunwell · Jul 7, 2020

Philz and mmarian and dobmatt...this is really helpful. The plastic card table sounds good. In my own experience (I2 and Mavic 2P); CompassCal has been required several times in places with no evident ferrous material....such as a field of dirt or gravel. Maybe other pilots can report their experiences launching from concrete parking garages. Thank you.

PhilZ · Jul 7, 2020

My comments were referring to my I2. My M2P is much more finicky with the compass.

sdunwell · Jul 7, 2020

Does the M2P like your card table trick? I plan to use both the I2 and the M2P on this job.

PhilZ · Jul 7, 2020

The M2P does not like the card table trick as much. The I2 has never complained. If you are using an M2, I would get a large cardboard box and place it on top of the card table. I have not done this myself, because I have always used the I2 for projects that require me to launch from the roof of a building or garage.

sdunwell · Jul 7, 2020

PhilZ said:
The M2P does not like the card table trick as much. The I2 has never complained. If you are using an M2, I would get a large cardboard box and place it on top of the card table. I have not done this myself, because I have always used the I2 for projects that require me to launch from the roof of a building or garage.

Thanks!

PhilZ · Jul 7, 2020

?. Good luck!

Donnie Frank · Jul 7, 2020

sdunwell said:
A new project requires launching from a very large concrete garage roof, then flying up 300' and over 100' to show a building site and views. There is no other nearby launch point on the ground, and several nearby buildings add congestion. Any suggestions for safe ops, especially regarding the compass? Would it help to use a table-top on saw-horses, or on an aluminum ladder to get away from the rebar while powering up? Several cycles of power up - power down will be needed. Really hoping to NOT calibrate compass on site. Inspire 2 and also Mavic 2 Pro will be used. Thanks!

Yes. Make sure you're on the roof with the bird...<:^0

I've personally had no problems launching from concrete and have done it many, many times. For extra assurance, I would go conduct test flights before the gig.

D

Dobmatt · Jul 7, 2020

sdunwell said:
Does the M2P like your card table trick? I plan to use both the I2 and the M2P on this job.

Let's make sure we are all on the same page ... We are talking about two different cases:

1. Frequent, but random Inspire 2 compass calibration requests.
2. Frequent, but software inflicted maintenance calibrations of Mavic 2 Pro compass.

First case was reported by some pilots after a particular FW update. The cause of such anomaly remains unknown (to my knowledge). Some pilots are reporting fix after .0400 FW installation (not officially downloadable, factory incarnation of .0300).

Second case is a result of either location change bigger than 50 km from a previous one, or timed out period between (2-3 months, if I'm not wrong).

Mavic 2 Pro seems to be more finicky with compass related things indeed. However, in urban jungle rare cases of sudden P-Mode switch to ATTI are known with all DJI models. It's magnetically and radio polluted environment after all, sporadical GPS blockade doesn't help either. Be aware and cautious.

sdunwell · Jul 8, 2020

Dobmatt said:
Let's make sure we are all on the same page ... We are talking about two different cases:

1. Frequent, but random Inspire 2 compass calibration requests.
2. Frequent, but software inflicted maintenance calibrations of Mavic 2 Pro compass.

First case was reported by some pilots after a particular FW update. The cause of such anomaly remains unknown (to my knowledge). Some pilots are reporting fix after .0400 FW installation (not officially downloadable, factory incarnation of .0300).

Second case is a result of either location change bigger than 50 km from a previous one, or timed out period between (2-3 months, if I'm not wrong).

Mavic 2 Pro seems to be more finicky with compass related things indeed. However, in urban jungle rare cases of sudden P-Mode switch to ATTI are known with all DJI models. It's magnetically and radio polluted environment after all, sporadical GPS blockade doesn't help either. Be aware and cautious.

Yes - a polluted environment. Maybe I can do the whole job with the I2. M2P was a supplement, as part of the job needs the X7 camera and most of the job does not.

BudWalker · Jul 11, 2020

sdunwell said:
A new project requires launching from a very large concrete garage roof, then flying up 300' and over 100' to show a building site and views. There is no other nearby launch point on the ground, and several nearby buildings add congestion. Any suggestions for safe ops, especially regarding the compass? Would it help to use a table-top on saw-horses, or on an aluminum ladder to get away from the rebar while powering up? Several cycles of power up - power down will be needed. Really hoping to NOT calibrate compass on site. Inspire 2 and also Mavic 2 Pro will be used. Thanks!

The single most effective method to prevent a fly away is to check that the heading shown on the map display agrees with the actual orientation of the AC.

If they don't agree that means the AC, for whatever reason, has the wrong heading value and erratic flight and/or flyaway is likely. One need not attempt to determine if launching from a table, raised arm, etc. will move the AC out of any geomagnetic distortion. Just check that the orientations are the same.