What is considered low when flying over water?

[dwolfe002]

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.

Yep, I have started doing it flying left to right in front of me. When I'm flying away from me it quickly looks like it's about an inch above the water and gets scary.

 

[dwolfe002]

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

I see that you are flying yours a little differently these days, like flying over water. I knew something seemed a little off about your answers to this topic. Before long you'll be giving me lessons.

Take care and happy flying!

 

[old man mavic]

I see that you are flying yours a little differently these days, like flying over water. I knew something seemed a little off about your answers to this topic. Before long you'll be giving me lessons.

Take care and happy flying!

yes you are right i did fly over water 2 days ago my first time and yes i was very conscious of the fact that if i had a problem it was by by mavic ,but i got some great video of the lake ,and enjoyed the experience ,and i will probably be doing it again in the future,finally i would never presume to give anyone lessons on flying, just helping them to keep their UAVs safe and offering help in that department i know how much my mav ownership means to me and i am sure to many others on this forum, you take care as well and happy flying to you

 

[Porky]

yes you are right i did fly over water 2 days ago my first time and yes i was very conscious of the fact that if i had a problem it was by by mavic ,but i got some great video of the lake ,and enjoyed the experience ,and i will probably be doing it again in the future,finally i would never presume to give anyone lessons on flying, just helping them to keep their UAVs safe and offering help in that department i know how much my mav ownership means to me and i am sure to many others on this forum, you take care as well and happy flying to you

Nice one dad, glad you tried it? I was the same as you, very nervous about flying over water but now I don’t think anything of it. It was a new challenge for me years ago but living right on the water edge I had to do it, well wanted too..

You will definitely get confident the more you try?

 

[Peio64270]

Very depending on waves height for my concern !

 

[Magilla Gorilla]

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!

I fly over a large clear water pond and usually cruise over it 10 feet or higher.

 

[Mavic Maveric]

I live near Lake Champlain (borders Vermont & New York) and will be flying over the lake this summer to take some video clips of summer water sports/fun for a video project that I'm planning. This will be my 1st Summer with my M2P. So as you can tell, I am completely inexperienced over water.

Here's a thought from a guy in the same boat you are that might help you decided what to do. From what I've researched and read here on this forum I plan to keep the minimum height at 6 feet (1.8 meters) above the surface. I am also probably going to buy some pontoons, ball type, they're somewhat unsightly but I've read they're more stable in the breeze than the "noodle" types. I will take them with me incase I'm feeling particularly insecure by the time I get to the water's edge.

Good luck and let us know how it goes!

 

[kilomikebravo]

DW: Living near the Gulf of Mexico, I too find myself over water fairly frequently but clearly, flying over a dead still pond or lake is far different than flying over the ocean and one needs to be wary of the differences.

Me? I'm not interested in either flying super low or, trying to grab video that close to the surface of any water (or ground for that matter.) IMHO, footage while flying at 20-50' (or even higher,) above the waves looks a lot better and is more pleasing to MY eyes than skimming the surface.

 

[dwolfe002]

DW: Living near the Gulf of Mexico, I too find myself over water fairly frequently but clearly, flying over a dead still pond or lake is far different than flying over the ocean and one needs to be wary of the differences.

Me? I'm not interested in either flying super low or, trying to grab video that close to the surface of any water (or ground for that matter.) IMHO, footage while flying at 20-50' (or even higher,) above the waves looks a lot better and is more pleasing to MY eyes than skimming the surface.

I agree. Most of my video is taken around your ranges, although I will dip down to 5 - 10 to get some shots that I like. But when I'm playing around I will get down to 2 ft and skim the water at full speed. Usually I'm not taking video at the time because all you can see are blurred small peaks of water and a lot of green. But, when I was preparing to do that, I asked about flying low over water and realized that everyone had a different opinion of what LOW was. I just thought if people that are asking for help or trying to help someone else with a question about flying low over water would put in the heights they are talking about it would really help. Just an example, you said you are not interested in flying super low. Now, since I fly at 2 ft. super low to me would be around 6 inches where to you it may be 2 ft. Someone else may think 5 ft was super low and say they do this or that maneuver all the time super low but it won't work the same at 6 inches. I just thought I would see if people might want to put in their actual altitude when talking low over water. I think it would help.

 

[Thoraldus]

English please!!!!!!!! hehe!

Google 'rf multipath distortion' ... There's a lot of good scary articles out there. ?

 

[dwolfe002]

Google 'rf multipath distortion' ... There's a lot of good scary articles out there. ?

Ok, got it. Now can you explain why this is important in this thread "What is considered low when flying over water".

 

[Thoraldus]

Ok, got it. Now can you explain why this is important in this thread "What is considered low when flying over water".

Because calm water can act as an efficient RF reflector sending a phase shifted signal to the AC receiver. The phase shifted signal might interfere with the correct interpretation of the control bit stream. Much of this depends on the design and quality of the receiver/decoder in the AC - all are not created equal.

From our friends over at Cisco ...

"
Effects of multipath distortion include:

Data Corruption—Occurs when multipath is so severe that the receiver is unable to detect the transmitted information.

Signal Nulling—Occurs when the reflected waves arrive exactly out of phase with the main signal and cancel the main signal completely.

Increased Signal Amplitude—Occurs when the reflected waves arrive in phase with the main signal and add on to the main signal thereby increasing the signal strength.

Decreased Signal Amplitude—Occurs when the reflected waves arrive out of phase to some extent with the main signal thereby reducing the signal amplitude."

 

[old man mavic]

Because calm water can act as an efficient RF reflector sending a phase shifted signal to the AC receiver. The phase shifted signal might interfere with the correct interpretation of the control bit stream. Much of this depends on the design and quality of the receiver/decoder in the AC - all are not created equal.

From our friends over at Cisco ...

"
Effects of multipath distortion include:

Data Corruption—Occurs when multipath is so severe that the receiver is unable to detect the transmitted information.

Signal Nulling—Occurs when the reflected waves arrive exactly out of phase with the main signal and cancel the main signal completely.

Increased Signal Amplitude—Occurs when the reflected waves arrive in phase with the main signal and add on to the main signal thereby increasing the signal strength.

Decreased Signal Amplitude—Occurs when the reflected waves arrive out of phase to some extent with the main signal thereby reducing the signal amplitude."

thanks @Thoraldus i mentioned it in post#3 and thought it could have an effect on the control of the drone, at the very low altitudes people were flying at, causing a loss of signal to the drone and adding an extra risk of a crash i had read somewhere that it can cause problems with the GPS as well and effect the number of sats being received by the GPS module

 

[dwolfe002]

Because calm water can act as an efficient RF reflector sending a phase shifted signal to the AC receiver. The phase shifted signal might interfere with the correct interpretation of the control bit stream. Much of this depends on the design and quality of the receiver/

Basically the same as a regular radio signal. I don't get the same song playing in three different phases when I'm at the beach under an umbrella. This problem has been taken care of long ago by people that want to put any kind of quality into their receivers or transmitters and I just don't see it as a problem. It is basically an echo cancelling circuit of which the design has been working for a long time.

 

[Thoraldus]

thanks @Thoraldus i mentioned it in post#3 and thought it could have an effect on the control of the drone, at the very low altitudes people were flying at, causing a loss of signal to the drone and adding an extra risk of a crash i had read somewhere that it can cause problems with the GPS as well and effect the number of sats being received by the GPS module

Hopefully DJI uses a 'diversity antenna system' to mitigate multipath distrotion.

Basically the same as a regular radio signal. I don't get the same song playing in three different phases when I'm at the beach under an umbrella. This problem has been taken care of long ago by people that want to put any kind of quality into their receivers or transmitters and I just don't see it as a problem. It is basically an echo cancelling circuit of which the design has been working for a long time.

Actually no, it's a serious issue for data (not music audio).

 

[dwolfe002]

Hopefully DJI uses a 'diversity antenna system' to mitigate multipath distrotion.

Actually no, it's a serious issue for data (not music audio).

But data has been transmitted wirelessly for many years. Now I haven't been in the field for at least 15 years but we transmitted wireless data over a sine wave. I wish I could remember the names of the filters but they were basically an echo canceler for digital or at least that's how we tied them into an analog world. I mostly dealt with telecommunications and a couple of years of cell service. Maybe things have changed due to low power digital transmission with all the technology changes. I don't know for sure but I can say I haven't had any problems with the M2P flying low over water and I'm talking 2 ft altitude. I think the longest distance I have been away is probably about 100 yards which to me was too far but I still didn't have any problems.

 

[FormerMember07122019_2]

The Mavic 2 is using Occusync 2.0 which utilizes OFDM for video and FHSS for data. Both of these very robust transmission architectures that are inherently relatively immune to interference problems. In addition, they are packet based systems. If a data packet get corrupted it just gets re-transmitted. Any problems with signal reflections are highly unlikely. And since both the controller and aircraft both have dual antennas I believe they utilize diversity principles because they are spaced at least a wavelength apart. The biggest concern for interference is from competing larger amplitude RF signals in the same spectrum (WiFi, cellular, etc) which have the potential to overwhelm the receiver input circuitry, effectively blocking the transmission.

 

[kilomikebravo]

super low to me would be around 6 inches where to you it may be 2 ft.

DW: I hear you and it's a valid question. However, I think most people would agree that two feet above the water is in fact "super low." And when you say that you do it at full throttle, well, to me that is simply asking for disaster. You may get lucky over a still pond or lake but it is a whole different ball of wax over ocean waves, even at the shore.

Best of luck and I hope you have hundreds of flights without issue.

 

[Peio64270]

DW: I hear you and it's a valid question. However, I think most people would agree that two feet above the water is in fact "super low." And when you say that you do it at full throttle, well, to me that is simply asking for disaster. You may get lucky over a still pond or lake but it is a whole different ball of wax over ocean waves, even at the shore.

Best of luck and I hope you have hundreds of flights without issue.

Absolutely. Altitude precision is not better than +/- 1m, specially when speeding. The changes of pitch induce variation in altitude that are not corrected instantaneously.

 

[dwolfe002]

DW: I hear you and it's a valid question. However, I think most people would agree that two feet above the water is in fact "super low." And when you say that you do it at full throttle, well, to me that is simply asking for disaster. You may get lucky over a still pond or lake but it is a whole different ball of wax over ocean waves, even at the shore.

Best of luck and I hope you have hundreds of flights without issue.

Don't get me wrong, @kilomikebravo and @Peio64270, I would never try to fly at 6 inches but I would consider that super low and not the 2 ft. that that others do. Flying at 2ft., while I don't do it during a normal flight, just seems to be one of those things that I can do that gets my blood pumping! But my point in asking the question is that everybody's low is different and I think it would be a good thing to say what that altitude is when asking a question or answering one when talking about flying low over water. I fly sometimes at 2 ft. and it's not at a smooth lake or pond, it is in Core Sound right by my house, sea water. Is it crazy? Yea, I'll give you that one. Will I probably loose my M2P to the depths? Probably one day or today! But I do it and it is my loss if anything happens and I know that. But for others that don't do such crazy things, if someone told me that banking while flying low worked just fine and they didn't know that I was talking at 2 ft altitude instead of 6 ft altitude that they were at then I might just try it at 2 and sink the Mavic. Like Peio said, the tolerance for the sensors is 1 meter +/-. But at the same time, flying low over land and water, rather quickly, I have found that the M2P stays remarkably level. But, flying over land at the same speeds and altitude with the sensors off it crashes. I would never tell someone to fly at my altitudes, it is very risky, but it seems that not knowing what altitude to fly at is also risky and could be fixed by telling members what they consider low.