How much does rebar in concrete affect takeoff?

[Meta4]

My Mavic 2 Pro asks for a compass calibration when I'm more than a few dozen km away from the last place I flew.

It might ... but it doesn't need it.
There's nothing about where you are on the planet that makes any difference to compass calibration.
Try ignoring it and see how it does.

 

[MAvic_South_Oz]

I keep a shallow plastic storage bin in my vehicle and launch from that when necessary. It is wide enough to hold my propeller guards, hoodman shade for ipad, etc. and gets the drone off the ground a few inches or so. It is also large enough to land on if I'm in an area with really loose dirt, dust such as camping in southern Utah.View attachment 148351

Nice option for flying out the back of your vehicle, and being practically set up ready to fly.

If you contact the top of that lid a relatively contrasting colour to most ground (fluro orange or red ?), precision landing should be reliable too.

 

[rexster1505]

I live in a concrete jungle. Almost every place I can find away from crowds are walkways or bike way, concrete decks with grass on top etc. So I read this is a problem because of rebar in sidewalks may interfere with the compass or IMU. My question is there a way to know if this is true or going to happen? If I start up the propellers and don't get an error message does it mean I am in the clear or is it possible I could have an instant fly away? Urban legend or real thing, has anyone actually experienced this first hand?

I know I had a problem getting off a part of concrete highway once with my Phantom 4 Pro

 

[Faster]

This is the best drone take off platform you can use. Your drone will never have any issues, or at least you won't notice it at all. Only condition is it has to be full.