Judging distance over water - not easy!

[Erroll]

I recently did a long distance flight out to sea to try and film a passing container vessel. As far as I could recall one can see close to 5km from sea level looking out to the horison, and having done 5km flights before, I thought that this would be doable.

I lost sight of the ship on my iPad and had to change course 2/3rds of the way out to get back on track, because I had not been compensating for the ship's speed. After 5.3 km my quad was not even close to the ship and I turned back. Quite difficult to judge distance over the water with no reference points.

The first picture below is a frame grab from just before I turned around (5.3km out) - one can hardly see the ship.
The second picture is of the coast line after I had turned around - adrenalin-pumpingly far away!

Another observation: - I had only one slight RC signal glitch (which I only saw after having uploaded the log to HD), but my video signal dropped several times during the sortie. I had set out at about 100ft ASL because the whole flight was going to be LOS, but even going up to about 300ft made little difference. Every few minutes my video signal would drop. Does the water have an effect on the video signal, but not the radio signal?
(Here is the HD link for those interested: HealthyDrones.com - Innovative flight data analysis that matters )

 

[happydays]

I would have thought that height would have increased the signal strength - maybe not?

 

[Wacker2611]

I recently did a long distance flight out to sea to try and film a passing container vessel. As far as I could recall one can see close to 5km from sea level looking out to the horison, and having done 5km flights before, I thought that this would be doable.

I lost sight of the ship on my iPad and had to change course 2/3rds of the way out to get back on track, because I had not been compensating for the ship's speed. After 5.3 km my quad was not even close to the ship and I turned back. Quite difficult to judge distance over the water with no reference points.

The first picture below is a frame grab from just before I turned around (5.3km out) - one can hardly see the ship.
The second picture is of the coast line after I had turned around - adrenalin-pumpingly far away!

View attachment 41672

View attachment 41673

Another observation: - I had only one slight RC signal glitch (which I only saw after having uploaded the log to HD), but my video signal dropped several times during the sortie. I had set out at about 100ft ASL because the whole flight was going to be LOS, but even going up to about 300ft made little difference. Every few minutes my video signal would drop. Does the water have an effect on the video signal, but not the radio signal?
(Here is the HD link for those interested: HealthyDrones.com - Innovative flight data analysis that matters )

To be fair and depending on what if any antenna mods you have, I think that's a pretty satisfactory distance to keep full control. It was only a minor glitch, and you were 5km away!

 

[Erroll]

I would have thought that height would have increased the signal strength - maybe not?

Yes, I thought so too.

I was too absorbed with being so far out over the ocean that I completely forgot about my windsurfers. It would have been a good test to employ them to see if they would have made any difference in that scenario.

 

[Erroll]

My understanding (which may or may not be correct) is that the wifi signal can reflect/bounce off water which inverts the signal waves. That secondary signal can then cancel out the main signal at times if the opposing amplitudes match up. Again, I'm not sure if this is true, but I too have experienced periodic wifi signal loss over water at much less distance than in your case.

Interesting.

 

[Erroll]

To be fair and depending on what if any antenna mods you have, I think that's a pretty satisfactory distance to keep full control. It was only a minor glitch, and you were 5km away!

I was flying a completely stock standard RC - no mods, and I am not complaining about the distance at all! I have done several 5km+ flights before and am supremely confident in the equipment.

I was just curious as to the loss of video signal over the water.

 

[happydays]

I wonder why I'm not seeing the original post from MapMaker53?

 

[Meta4]

I recently did a long distance flight out to sea to try and film a passing container vessel. As far as I could recall one can see close to 5km from sea level looking out to the horison, and having done 5km flights before, I thought that this would be doable.

Wow .. 5km is a long way to go offshore and you'd definitely want to make sure you're not going to be pushing a headwind coming home from out there.
If you are chasing ships, it pays to find somewhere they approach closer than 5km.
With a little practice you can work out when to launch to intercept at a suitable point.
Ships are great subjects and shots of them at sea can be pretty special.

To help you with ships and distances, get an app for your phone called Marinetraffic.
That will show you where the ships are, how fast they are traveling and you can use the scalebar to estimate distance or they have a function to calculate how far using the GPS in your phone.
Here's a screenshot:

 

[Erroll]

Thank you. That is very informative.

Alas, I am from Johannesburg and only very seldom get to fly at the coast.

I am curious - your screen shot is of Durban?

 

[dirkclod]

I wonder why I'm not seeing the original post from MapMaker53?

He might have been deleting his post as it was being quoted happy . Have had that done before .
Tried to delete and got caught

 

[happydays]

He might have been deleting his post as it was being quoted happy . Have had that done before .
Tried to delete and got caught

Good answer. Thought I'd been blocked!

 

[Erroll]

He might have been deleting his post as it was being quoted happy . Have had that done before .
Tried to delete and got caught

I can't imagine why he would not want that post to be quoted.....?

 

[dirkclod]

I can't imagine why he would not want that post to be quoted.....?

I don't ether but was just saying I have had that happen before .

 

[CCDD]

Perhaps I'm a bit confused, how can one fly LOS if their Phantom is out 5km +? Doesn't LOS mean you still have a visual of your bird? I don't believe one could possibly see their Phantom from that far away unless they're using binoculars or something similar.

 

[dirkclod]

Perhaps I'm a bit confused, how can one fly LOS if their Phantom is out 5km +? Doesn't LOS mean you still have a visual of your bird? I don't believe one could possibly see their Phantom from that far away unless they're using binoculars or something similar.

You mean VLOS . LOS is between your TX and RC .

 

[CCDD]

You mean VLOS . LOS is between your TX and RC .

Ahh, thanks for the explanation. I meant VLOS, and the op was referring to LOS. My bad

 

[dirkclod]

Ahh, thanks for the explanation. I meant VLOS, and the op was referring to LOS. My bad

No problems ..I have a lot of bad's

 

[Solar Deity]

I'm bored, and in to making graphics today.

SD

 

[CCDD]

Helpful!!

 

[Erroll]

Perhaps I'm a bit confused, how can one fly LOS if their Phantom is out 5km +? Doesn't LOS mean you still have a visual of your bird? I don't believe one could possibly see their Phantom from that far away unless they're using binoculars or something similar.

Eish! I could hardly see a container vessel at that distance!!