Shooting inside a canyon question.

[Thiago1029]

im a newby and in a few months I'll be taking a kayaking trip to a place called Black canyon on the Colorado river. These canyon walls can be 120 feet tall on both sides of the river. Would I have trouble flying my mavic between these walls? What about loosing signal? Satelite etc? Off course I won't fly it around corners and I'll always have visual contact.
Thank you

 

[Qoncussion]

If you retain line of sight, and perhaps set RTH to hover - to avoid any overhead obstacles, you should be fine. I fly in canyons often with no problems.

 

[BorisTheSpider]

RTH to hover is a good suggestion. I'd also suggest tripod mode maybe, obstacle avoidance off so it won't do anything unexpected and preferably prop guards too.

 

[Qoncussion]

Ahh yes, what Boris said, and definitely turn off downward obstacle avoidance when flying over water.

 

[tcope]

Changes are _very_ good that you won't have enough sats locked for GPS to work (depends more on the width of the canyon). However, it will still fly just fine.

Not sure what "downward obstacle avoidance" is. I'd certainly leave obstacle avoidance on and I don't see any reason to turn VPS off. Some turn it off when flying over water though. Go slow.

 

[BorisTheSpider]

Yeah I meant more to turn off forward obstacle avoidance - if you're expecting to be flying close to obstacles (canyon walls) you probably don't want it impeding your control.

 

[Thiago1029]

If you retain line of sight, and perhaps set RTH to hover - to avoid any overhead obstacles, you should be fine. I fly in canyons often with no problems.

Thank for the reply.
Being a newby, I have to look up RTH. Don't know what that is.
Since you're the first who replied, do you happen to know any video tutorials I could watch to help me get started in this drone world?

 

[Qoncussion]

Sorry - meant disable downward positioning system... Especially over water, as the OP said this is a kayaking trip, and water beneath the craft has caused problems for some people.

 

[Qoncussion]

Thank for the reply.
Being a newby, I have to look up RTH. Don't know what that is.
Since you're the first who replied, do you happen to know any video tutorials I could watch to help me get started in this drone world?

You are most welcome... Head over to YouTube, search for Mavic Pro, and pull out a bucket of popcorn.

 

[BorisTheSpider]

In a canyon, downward positioning is something you definitely do not want to turn off. As someone else said your GPS signal will be poor, so the visual positioning will be the only way the mavic will hold position properly - if it's turned off, or you go outside it's limits, you'll be in ATTI mode which probably won't end well.

The GPS being poor is actually quite a threat since if it flicks in and out with inaccurate position fixes the drone might try to move where it thinks it should be, staight into an obstacle. You may wish to consider blocking the GPS with metal tape as a poor GPS signal in this situation is worse than none at all.

 

[royalhghnss]

In a canyon, downward positioning is something you definitely do not want to turn off. As someone else said your GPS signal will be poor, so the visual positioning will be the only way the mavic will hold position properly - if it's turned off, or you go outside it's limits, you'll be in ATTI mode which probably won't end well.

The GPS being poor is actually quite a threat since if it flicks in and out with inaccurate position fixes the drone might try to move where it thinks it should be, staight into an obstacle. You may wish to consider blocking the GPS with metal tape as a poor GPS signal in this situation is worse than none at all.

Downward positioning and visual positioning are two different things. One uses sonar (downward), the other (visual) uses a camera.

 

[BorisTheSpider]

Downward positioning and visual positioning are two different things. One uses sonar (downward), the other (visual) uses a camera.

OK I wasn't actually aware they were switchable separately - I thought the optical and sonar sensors worked together as one downward positioning system.

 

[royalhghnss]

OK I wasn't actually aware they were switchable separately - I thought the optical and sonar sensors worked together as one downward positioning system.

I could be wrong, but I don't think you can even turn off the visual positioning. The downward sensor just makes sure you don't lower the drone onto anything going too fast (uses sonar to gauge distance). The visual positioning is used to maintain position when GPS isn't working (ATTI mode). It takes a picture often, and tries to stay in the same spot by comparing pics. It works best on non-uniform surfaces.

 

[BorisTheSpider]

I could be wrong, but I don't think you can even turn off the visual positioning. The downward sensor just makes sure you don't lower the drone onto anything going too fast (uses sonar to gauge distance). The visual positioning is used to maintain position when GPS isn't working (ATTI mode). It takes a picture often, and tries to stay in the same spot by comparing pics. It works best on non-uniform surfaces.

I'm not sure - I thought the reason that it was recommended to turn off downward vps when flying over water was because the mavic could visually lock onto moving water then move with it when it shouldn't. That whole issue had given me the impression that what you were turning off in that scenario was the visual sensors, or perhaps both the visual and sonar sensors together as a unit.

 

[Bunny Too]

I'm not sure - I thought the reason that it was recommended to turn off downward vps when flying over water was because the mavic could visually lock onto moving water then move with it when it shouldn't. That whole issue had given me the impression that what you were turning off in that scenario was the visual sensors, or perhaps both the visual and sonar sensors together as a unit.

I think the reason VPS is recommended off is the water can distort the ultrasonic and make it think it is only inches above the surface and cause it to go into landing mode.
Regards,
-d.

 

[BorisTheSpider]

I'm no expert, but I thought sonar worked like radar based on the return time for a pulse, so a ping of ultrasound is transmitted, then the time it takes to return is measured and that tells you how far away the surface is.

Possibly moving water does interfere with that in some way, but it's more intuitive to me to think it would interfere with a visual system trying to lock on to a pattern that is assumed to be static like a floor or ground texture, but when the pattern is moving the system doesn't work.

I could be totally wrong of course, and if anyone knows for sure I'd be interested to find out more.

 

[Bunny Too]

I'm no expert, but I thought sonar worked like radar based on the return time for a pulse, so a ping of ultrasound is transmitted, then the time it takes to return is measured and that tells you how far away the surface is.

Possibly moving water does interfere with that in some way, but it's more intuitive to me to think it would interfere with a visual system trying to lock on to a pattern that is assumed to be static like a floor or ground texture, but when the pattern is moving the system doesn't work.

I could be totally wrong of course, and if anyone knows for sure I'd be interested to find out more.

You are correct, the two cameras look for patterns and help horizontal stabilization, the ultrasonic sensors bounce back and help with vertical stability. Water interferes with both (this only applies to altitudes of less than 13 meters.)
Regards,
-d

 

[Gary cato]

I think the reason VPS is recommended off is the water can distort the ultrasonic and make it think it is only inches above the surface and cause it to go into landing mode.
Regards,
-d.

Switching off the landing check has been said to cure the auto land problem, VPS can be left on over land, Auto-land has been known to happen at altitude as well if reflections create sensor confusion. Turning of the landing check allows control to be maintained without auto land cutting in.

Over water the downward VPS should be turned off, it creates a similar problem as auto-land as in the sensors become confused at what height the Mavic is actually at, it has been known to slowly descend into the water as the sensors again get confused.

The second problem can create the autoland over water at low heights, when it believes it is close to the ground and the autoland can no longer be aborted by stick up. It will hit the water and be a duck before you can hot the sport toggle button to disable auto land.

This is all what i believe and i could be wrong is the consensus of opinion. i am happy to be corrected.