Urgent help needed on filming maxi 72 sailing boat race

geigy · Jul 7, 2017

Oops, didn't mean to sound critical.

My only quibble is with the physics behind it, not the way you went about recovering your drone, which showed a lot of skill. Kudos to you, sir!

Vasco · Jul 7, 2017

Spy , good morning. Any footage from race so far????

Lake_Flyer · Jul 7, 2017

Grauniadangel said:
'Green Cross Code' and how it effects pedestrians should be standard knowledge for every (UK) pedestrian.

I should have said: every serious UAV pilot.
The OP's operation was quite a serious one. Not a recreational walk in the park.

Grauniadangel · Jul 7, 2017

I was hoping that you might elucidate for the questioner rather than stating ' you should know what you're doing'; how will people learn if they don't ask questions?

No offence or aggression intended.

Lelantos · Jul 7, 2017

Spy_Corfu said:
As i am not a airline pilot so I can not insinst in my hypothesis. You have a point .. you are saying there is equal resistance going at say 20-30 degrees to the wind? Maybe what did it for my was the fact that i slowly redused altitude and because of the montain behind me the wind force was redused.

Zig zagging will not help make way into a headwind with an aircraft. Sailboats zig zag (tack) because they have no choice. A sailboat cannot sail directly into the wind, they have to sail at an angle to the wind while using the keel to act against the water in order to make headway.

There is equal resistance no matter what direction you are flying your drone. Once the drone (any aircraft) becomes airborne, what the ground is doing beneath it is irrelevant. As far as it is concerned, it only experiences wind of its own making - by pulling itself through the airmass. This is a concept that many pilots do not understand - even some instructors. So don't feel bad if you don't find it intuitive.

Imagine you are swimming in a river, as hard as you can, but you cannot make any progress up river. The river is flowing as fast as you can swim. Now turn 30 degrees and swim as hard as you can. Do you make any progress up river? No, you don't. But you do make progress sideways, and once you reach the river bank you will find yourself a bit downstream of where you started. The longer you swim at an angle to the river, the further downstream you go.

What probably happened is that either the wind reduced in velocity or changed direction or both. Windspeed's are almost always higher as altitude increases. This is due to the wind gradient. Reducing altitude is generally your best bet when fighting a headwind.

jimmybbq · Jul 7, 2017

I believe Litchi addressed the focus problem in the latest update, at least that's what the change log states.

Spy_Corfu · Jul 7, 2017

In any case back to my original questions.. today was day 4 and last day of the maxi 72 race and again had some issues even after calibration of sensors and reading comments and manuals..
Focus over the sea was still an issue .. it refused to focus when i pressed on the screen and i had to get close to one of the boats to get the mavic to focus. Manual focus to infinity not sure if it worked properly as i could barely see the screen of my phone due to strong sun light.. I really preferred the phantoms fixed focus camera!!
Active tracking at the start did not work .. i still got message of front sensor error.. but then when i changed the battery i had another go later on during the race it worked just fine..
Any ideas what is happening with the sensors..? as i said later on they worked..
Last but not least i was 2 minutes away from loosing my mavic to the deep ocean!! Although i recorded the home point several times before and after pressing RTH as ME and not taking off location it did not work!! the drone was going at the wrong direction and i could see from the map trace that the gps position of my boat was wrong and it was not going where i was.
Because of the strong sun light i could not see much on my screen and i could definitively not find my boat!! Strong winds big waves and all that of course ....
Just about when i panicked i saw from my mobile phone screen a sailing boat which was not too far from the drone and not too far from me either as it was big enough not to be mistaken for another boat as there where others also around that area! so i raced the drone and my boat towards the same sailing boat which was not moving and as i said 2 mins before the end i caught it!
Now why did the RTH to my location did not work? my iPhone 7 has GPS and 4g was working etc etc..evern tried google maps to see if it was working and it seem to work... problem was maybe the accuracy?? usually i get 5m aprox. of accuracy but this time if was more like 100m off my current location.

wolfmad · Jul 7, 2017

Is your 7 on AT&T?

geigy · Jul 8, 2017

Once again, good job thinking on your feet and getting your drone back again!

Setting home to my location locks in the location at the time you set it. The home point does not follow you continuously, though that would be a convenient feature. As it is, you need to set the home point, and stay in one location, before invoking RTH.

For this reason, over water, it is preferable to have the drone hover if it loses signal, rather than RTH. This gives you time to either locate your drone and regain control, or set a new home point so that you can use the radar to fly back.

Spy_Corfu · Jul 8, 2017

Vasco said:
Spy , good morning. Any footage from race so far????

Videos:

and some photos:

https://photos.google.com/share/AF1...?key=R3o3Q3FZdEtXRDJyN05mSHM5UGtQQmpLTGowV0Z3

Spy_Corfu · Jul 8, 2017

Lelantos said:
Zig zagging will not help make way into a headwind with an aircraft. Sailboats zig zag (tack) because they have no choice. A sailboat cannot sail directly into the wind, they have to sail at an angle to the wind while using the keel to act against the water in order to make headway.

There is equal resistance no matter what direction you are flying your drone. Once the drone (any aircraft) becomes airborne, what the ground is doing beneath it is irrelevant. As far as it is concerned, it only experiences wind of its own making - by pulling itself through the airmass. This is a concept that many pilots do not understand - even some instructors. So don't feel bad if you don't find it intuitive.

Imagine you are swimming in a river, as hard as you can, but you cannot make any progress up river. The river is flowing as fast as you can swim. Now turn 30 degrees and swim as hard as you can. Do you make any progress up river? No, you don't. But you do make progress sideways, and once you reach the river bank you will find yourself a bit downstream of where you started. The longer you swim at an angle to the river, the further downstream you go.

What probably happened is that either the wind reduced in velocity or changed direction or both. Windspeed's are almost always higher as altitude increases. This is due to the wind gradient. Reducing altitude is generally your best bet when fighting a headwind.

Excellent explanations!.. thanks!.. especially with the river i get it now.. you are right of course..
In any case i was fortunate but another guy i saw a video flying from a beach did not get so lucky and you can see it all on his video.. he flow far far away with the wind and of course could get back ..

Spy_Corfu · Jul 8, 2017

jimmybbq said:
I believe Litchi addressed the focus problem in the latest update, at least that's what the change log states.

There was an update yesterday and i will try it..
Before that if you had the auto record on there was a one it two chances you get out focus video during a mission.

Seriously this variable focus is getting on my nerves .. i wish it was that simple as with the phantom models..

There are occasions when either i am in a hurry or the sun is too bright and i cannot see if the camera is out of focus or not and then all the footage is wasted.

99% of the videos taken from the magic are taken at a great distance with focus set to infinity in any case.. who uses short distance shots?

Spy_Corfu · Jul 8, 2017

wolfmad said:
Is your 7 on AT&T?

Now i am flying from Corfu - Greece but its 4g network so very fast (over 70mbps) and usually no problems with google maps when driving..
Maybe when at sea there are other factors effecting the gps accuracy??
i will have to try it on firm ground soon so i am ready next time i need to use it..

Spy_Corfu · Jul 8, 2017

geigy said:
Once again, good job thinking on your feet and getting your drone back again!

Setting home to my location locks in the location at the time you set it. The home point does not follow you continuously, though that would be a convenient feature. As it is, you need to set the home point, and stay in one location, before invoking RTH.

For this reason, over water, it is preferable to have the drone hover if it loses signal, rather than RTH. This gives you time to either locate your drone and regain control, or set a new home point so that you can use the radar to fly back.

Aha! can you elaborate on the last part "...or set a new home point so that you can use the radar to fly back."

When i saw it was not going towards my boat as i was drifting i cancelled RTH and then set RTH position as me again but did not notice any changes in the radar screen .. the blue dot (me i guess) was at the same point as the drone and the initial taking off position..

There would have been another line white or yellow so i could point the arrow towards me ..

I have used this feature many times to return my drone towards me but i am always at the start position.

Will have to do some experiments for sure to get this right for next time!