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What is considered low when flying over water?

dwolfe002

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I can't drive one mile as the crow flies in three directions without hitting a large body of water so that is where I fly. Now every once in a while, I like to fly low over the water and people were trying to warn me away from doing that. They were just trying to keep me from losing my M2P and I appreciate that. But, I also received replies that other people flew low over water all the time but I found out quickly that low is in the eye of the beholder. Most don't say what that altitude is. Like me, when I fly low, I'm talking 2 - 3 feet. At the same time others are talking 5-6 and others 10-12 and so on. I got to thinking that some replies were only applicable if their definition of low was the same as mine. So, I figured I would ask everyone, "What do you consider low when flying over water?" and, if you think adding the height you are flying at in posting a question or a response to a question concerning "low" would be helpful to everyone.

Take care and happy flying!
 
Certainly a matter of opinion and probably no clear consensus on the numbers. Risk verses reward?
 
one of the problems of flying low over any surface is the fact that a lot of the signal gets diffused by the ground because the signal bounces off the surface there is a technical name for it ,but it escapes me at the moment,i think that flying at the heights you mentioned,would be very risky but if you think it is worth the risk then that is a judgment call you have to make for yourself
 
@dwolfe002

I like your idea of a post about low flight ( over water, trees, tall grassy meadows, crops, etc) to include a clearance height.

Ultrasonic sensors for obstacle and terrain avoidance seem to work equally well over water and land. Aircraft that use IR (infra-red) sensors for altitude assessment and control can find calm glassy water to be a bit of a problem.

One thing to watch during very low flight (< 5 feet) is avoiding down throttle while steering the aircraft with yaw inputs. The margin for error is very slim, especially when the aircraft is out some distance and actual height is hard to visually determine.
 
Certainly a matter of opinion and probably no clear consensus on the numbers. Risk verses reward?

That was mainly my reason for asking. If people wouldn't mind putting an actual height in their posts it may help, whether it's a question or response. If I'm talking about low as 10' and the poster is talking about low at 3', it would probably change my answer if I knew that and maybe save a few drones in the process.
 
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When I fly over water, commonly over my pond, I am at 4-6 ft at the low end but have probably dipped as low as 3 ft. The concern I have in going any lower is that the M2 landing detection threshold is specified at 1.6 ft (0.5m). Around this height if you try to go any lower (and in a hover ) it may try to land. This is more problematic if you consider the possibilities of reflections off the water that can confuse the sensor and cause unknown behavior. Now, if you are moving along the water at a low level and are expecting the lower sensor to maintain the minimum altitude it may not be able due to these same reflections.
 
one of the problems of flying low over any surface is the fact that a lot of the signal gets diffused by the ground because the signal bounces off the surface there is a technical name for it ,but it escapes me at the moment,i think that flying at the heights you mentioned,would be very risky but if you think it is worth the risk then that is a judgment call you have to make for yourself

Hello Old Man Mavic. Hope you are still doing good. Flying at the heights I do is very risky and I know that. While knowing I could loose my M2P at anytime, I just like to do it sometimes and am willing to take that risk. But I have found that my low is different than others low and people need to be aware of that when asking or responding to someone. There are plenty of things that I wouldn't try at 3 ft. that I would quickly try at 10ft. So, I just thought that it would help everyone with questions or answers to understand the full circumstances. In fact, speed and sensors could be brought into the same conversation because I have seen videos of people hovering over water and just dropping down into it but haven't seen one just descend into water while moving at speed.
 
one of the problems of flying low over any surface is the fact that a lot of the signal gets diffused by the ground because the signal bounces off the surface there is a technical name for it ,but it escapes me at the moment,i think that flying at the heights you mentioned,would be very risky but if you think it is worth the risk then that is a judgment call you have to make for yourself
Maybe this... Radio waves from a single source taking multiple routes to a receiver can arrive out of phase causing destructive interference. Or not...
 
Hello Old Man Mavic. Hope you are still doing good. Flying at the heights I do is very risky and I know that. While knowing I could loose my M2P at anytime, I just like to do it sometimes and am willing to take that risk. But I have found that my low is different than others low and people need to be aware of that when asking or responding to someone. There are plenty of things that I wouldn't try at 3 ft. that I would quickly try at 10ft. So, I just thought that it would help everyone with questions or answers to understand the full circumstances. In fact, speed and sensors could be brought into the same conversation because I have seen videos of people hovering over water and just dropping down into it but haven't seen one just descend into water while moving at speed.
we all fly our UAVs differently,and i am sure that none of us want to see any ones bird end up in the water or have a heavy crash,we all know how much they cost ,and apart from a few speaking for myself i would be heartbroken,if my mav ended up destroyed,whatever sort of risks we take with our UAVs it is our choice to make at the time keep flying the way you are happy with
 
When I fly over water, commonly over my pond, I am at 4-6 ft at the low end but have probably dipped as low as 3 ft. The concern I have in going any lower is that the M2 landing detection threshold is specified at 1.6 ft (0.5m). Around this height if you try to go any lower (and in a hover ) it may try to land. This is more problematic if you consider the possibilities of reflections off the water that can confuse the sensor and cause unknown behavior. Now, if you are moving along the water at a low level and are expecting the lower sensor to maintain the minimum altitude it may not be able due to these same reflections.

I didn't know about the landing detection threshold. That could easily cause one at hover to sink into the unknown. The other thing about moving at speed really has me worried. I don't fly over water at 2' slowly. I'm usually going 15 to 20 mph. and with all sensors on the M2P seems to hold altitude very well. However, when trying the same thing over land at the same speed without the sensors off I crashed as many times as I didn't. I know per documentation that the sensors are not supposed to work at these speeds but at the same time, I haven't crashed with them on and don't really know what to think. I guess I should put up a disclaimer: THIS IS NOT RECOMENDED IF YOU HAVE AN AVERSION TO CRASHES.
 
I can't drive one mile as the crow flies in three directions without hitting a large body of water so that is where I fly. Now every once in a while, I like to fly low over the water and people were trying to warn me away from doing that. They were just trying to keep me from losing my M2P and I appreciate that. But, I also received replies that other people flew low over water all the time but I found out quickly that low is in the eye of the beholder. Most don't say what that altitude is. Like me, when I fly low, I'm talking 2 - 3 feet. At the same time others are talking 5-6 and others 10-12 and so on. I got to thinking that some replies were only applicable if their definition of low was the same as mine. So, I figured I would ask everyone, "What do you consider low when flying over water?" and, if you think adding the height you are flying at in posting a question or a response to a question concerning "low" would be helpful to everyone.

Take care and happy flying!

When it comes to flying over the water with good a line of sight which is really easy to do 2 to 3 ft is comfortable over a lake with both the Phantom and the Mavic. All sensors and landing sensors turned off.

When it comes to flying over the trees 3 to 5 is about where we stay do to the line of sight being much more difficult.

The only benefits you get of course is the increased adventure and the Video looks really inspiring to watch as its an intense view point watching back on camera the drone appearing so close .

As far as speed goes for these low end flights P mode 10 to 20

Phantomrain.org
Gear to fly your Mavic in and out of the Storm
 
I didn't know about the landing detection threshold. That could easily cause one at hover to sink into the unknown. The other thing about moving at speed really has me worried. I don't fly over water at 2' slowly. I'm usually going 15 to 20 mph. and with all sensors on the M2P seems to hold altitude very well. However, when trying the same thing over land at the same speed without the sensors off I crashed as many times as I didn't. I know per documentation that the sensors are not supposed to work at these speeds but at the same time, I haven't crashed with them on and don't really know what to think. I guess I should put up a disclaimer: THIS IS NOT RECOMENDED IF YOU HAVE AN AVERSION TO CRASHES.

The sensors have many limitations. In addition to lighting, and textures, and physical size (small objects) there are speed limitations. The quote below is from the manual.

“Note that the Vision System may NOT function properly when the aircraft is flying too fast. Fly with caution when flying at over 10 m/s (32.8 ft/s) at 2 m (6.6 ft) or over 5 m/s (16.4 ft) at 1 m (3.3 ft).”

Translated it says less than 22 mph at 6.6 ft and 11 mph at 3.3 ft. And the water adds an additional complication.
 
When it comes to flying over the water with good a line of sight which is really easy to do 2 to 3 ft is comfortable over a lake with both the Phantom and the Mavic. All sensors and landing sensors turned off.

When it comes to flying over the trees 3 to 5 is about where we stay do to the line of sight being much more difficult.

The only benefits you get of course is the increased adventure and the Video looks really inspiring to watch as its an intense view point watching back on camera the drone appearing so close .

As far as speed goes for these low end flights P mode 10 to 20

Phantomrain.org
Gear to fly your Mavic in and out of the Storm

I figured you would have a lot of experience flying over water. The problem I have had is with the sensors off, flying over land, at about 2'. The M2P seems to want do go into a dive and of course there is no way to stop it in time. With my sensors on it always seems to fly very level although the sensors shouldn't be working at 15 to 20 mph. I have no idea why mine does this but I keep my sensors on.
 
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The sensors have many limitations. In addition to lighting, and textures, and physical size (small objects) there are speed limitations. The quote below is from the manual.

“Note that the Vision System may NOT function properly when the aircraft is flying too fast. Fly with caution when flying at over 10 m/s (32.8 ft/s) at 2 m (6.6 ft) or over 5 m/s (16.4 ft) at 1 m (3.3 ft).”

Translated it says less than 22 mph at 6.6 ft and 11 mph at 3.3 ft. And the water adds an additional complication.

Thanks Ken. I saw that in the manual and at the time didn't want to translate it to something useful. Although I don't rely on them when flying so close to water, they do (or something does) seem to keep the mavic from dipping down and flying what I would call extremely level. Now I don't do it for very long, maybe 75 to 100 ft. and then I get nervous and think I'm pushing my luck but so far that's the way it is working in my case. I wouldn't even think of turning the sensors off at 2'.
 
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I figured you would have a lot of experience flying over water. The problem I have had is with the sensors off, flying over land, at about 2'. The M2P seems to want do go into a dive and of course there is no way to stop it in time. With my sensors on it always seems to fly very level although the sensors shouldn't be working at 15 to 20 mph. I have no idea why mine does this but I keep my sensors on.

When you say dive , do you mean land ?
if so make you have the landing protection turned off.
 
When you say dive , do you mean land ?
if so make you have the landing protection turned off.

No, it's just diving into the dirt with everything turned off although it is right after a dive from about 30 to 40 ft pull out of the dive so the M2P ends up going horizontal at around 2 ft and sometimes inches lower and around 15 to 20 mph forward. I have only tried it four times and it crashed twice. Both times it crashed it just seemed to all of a sudden turn downward. Then I quit trying. The place I practice at is a soccer field so there isn't much if any slope. I have done it many times successfully with all sensors on although the front sensors sometime cut the dive short and simply stop the M2P in its tracks.
 
With the sensors off I would hazard a guess that you are dealing with lag from the barometer. The experts here will likely have a better idea though.
 
No, it's just diving into the dirt with everything turned off although it is right after a dive from about 30 to 40 ft pull out of the dive so the M2P ends up going horizontal at around 2 ft and sometimes inches lower and around 15 to 20 mph forward. I have only tried it four times and it crashed twice. Both times it crashed it just seemed to all of a sudden turn downward. Then I quit trying. The place I practice at is a soccer field so there isn't much if any slope. I have done it many times successfully with all sensors on although the front sensors sometime cut the dive short and simply stop the M2P in its tracks.

All these aircraft tend to lose a bit of vertical control when large pitch or roll excursions are applied, such as stopping suddenly. Maybe the motors don't spool up quite fast enough to compensate for the large attitude. Either way, it is common for them to lose a couple of meters of altitude on a rapid stop - that's put many aircraft into the ground or water.
 
For me, it’s more a function of how far mavic is from my eyeballs.

If it’s super close and I my eyes are aligned with the drone, I don’t mind flying within 2-3 feet

As it gets further away, even like 50-100 yards, it’s more difficult to perceive the distance between mavic and the water and I tend to fly higher above the surface.
 
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