Flying Over Water Question

[Bret]

I tried to perform a Cable Cam smart shot over the weekend and had some issues. The cable cam appeared to have set up properly but when I ran the cable back, about halfway through the cable, it appeared to have lost altitude. I am at a loss as to why. I know there is no boat mode but I was able to take off from the deck of my boat. Below, I have a video showing me setting up the cable and running it back. Any ideas?

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[quick_dry]

When it starts to drop altitude, is it in the boat's exhaust plume and could that cause the baro to report the wrong altitude? try flying a few other times through the exhaust and see if you get altitude changes (though isn't the PH2 temp compensated?)

 

[RichWest]

LOL....sorry, you realizing your bird was sitting close to the water was priceless....glad it wasn't worse.

Several factors. The barometer is only going to be so accurate, I would suggest anticipating a 2M variance which is what appeared to have happened. Speed of flight during a MPCC will effect altitude either by design or air pressure. MPCC's run a smooth transition through "points", stated as Bézier curves which will allow an "overshoot" and in this case elevation as you were coming down into the shot.

If you would have started the MPCC at the lower altitude and went up it would have maintained the altitude for the first two points and then overshoot the vertical point of the transition wide. Slow down the MPCC and the overshoot will be reduced. Speed it up and expect a wild ride...

 

[User Name]

Wow, that was CLOSE!!!

Word of advice - ALWAYS test your cable cams from start to finish before taking your eyes off it and just expecting them to fly perfectly.

Rich beat me to it, but this is what I was typing when he posted:

I suspect the issue (not that it's really an issue) is the nature of the path that's generated through your points. One of Solo's best features is how it flies a smooth path between the points you set. To do so, it generates a curve that goes through your points, but will overshoot each one to smooth the path out. In the pic below, all 3 points are at the same height, but you can see that the curve overshoots each one. These curves will be more extreme the tighter the "corner" is between the points before and after a given point. Your points varied from close in to a ways out and Solo had to make somewhat drastic changes of direction to fly through them. Large changes in x, y axes (left/right/forward/back) can make the curve exaggerate smaller changes in the z axis (up/down). Also, the speed at which you fly the cables will effect how much it'll overshoot each point - if you're going faster, it'll overshoot each point by a greater degree.

Lastly, while the barometer is amazingly accurate at detecting small changes in pressure and so being able to maintain the drone at a fixed altitude, I think it's less accurate when trying to fly back to a precise altitude. Think of it like squeezing something between your fingers - you can maintain a pretty good, consistent pressure while you're holding something, but if you were to put it down, pick it back up and try to hit that exact same pressure, you'd probably be a ways off.

Which brings me back to my first point - always test fly your cables!

 

[Mountain Flyer]

Keep in mind that the GPS bubble that solo can maintain is a meter or more in diameter as well. These use a civilian based GPS unit that is not as accurate as military grade and a stock Solo only uses USA satellites. When doing cables over water I would never set the altitude lower than ten or fifteen feet over the surface and even that is probably taking some risk. When Solo is up in the air and away from you it is hard to tell how much they really move around while 'locked' in place. If you were to hover one at ten feet for a few minutes and watch it closely you would notice that they do move around a lot more than is noticeable in an average flight. My own experimenting with the stock GPS led me to replace it with the mRo GPS chip for a lot better accuracy. I would still not set cable way points closer than 10 to 15 feet above the surface of whatever I am flying over. When you set the original way point near the waters surface Solo may or may not have recorded the actual altitude it was at then. It could also have recorded that location at half a meter in any given direction. When coming back to that way point it looks for a certain level of accuracy again for that spot but could again be off by half a meter or more. Solo also uses barometric pressure to gauge altitude and that close to the surface it could be thrown off by water temp or winds. Solo is accurate to a degree but don't ever expect it to do exactly what you set it to do. The systems are just not that good yet for us civilians and some leeway should be given when setting way points to account for this. I forget the exact window that Solo gives itself for accuracy on passing through way points but my memory is saying 2 meters. That is a significant amount of allowable error to be setting cables close to the surface or other objects. It probably says more about it in the manual.

 

[Bret]

Wow! Thanks for the great detailed responses! I am still a clueless newbie, but am trying hard to learn as much as I can. I realized that I just learned a very lesson in that always test run any smart shot before running it for real. The distance variation is definitely opened my eyes and I will most assuredly take them into account from here on out!

Thanks for the quick responses! I grounded myself since this incident happened (last Friday) until I had a chance to investigate this issue.

 

[RichWest]

I grounded myself since this incident happened (last Friday) until I had a chance to investigate this issue.

And to clean your britches.....LOL!

 

[Bret]

And to clean your britches.....LOL!

YEP!! lmao

 

[RichWest]

Rich beat me to it, but this is what I was typing when he posted:

Your explanation was better, I was cleaning my keyboard from the video. Again, not at you Bret....we've all been there more than once, possibly not as lucky as you, but been there and done that.

 

[ChrisM101]

Its a good looking cable cam ... minus the Ranger boat... (Im a Triton Guy) They are right about the curves and gps and such, but ive always noticed that going from land (the boat in this case) to water the barometric pressure seems to affect its accuracy. ive also experienced this when going from low to elevated land like over a retaining wall that has land behind it or being on a retaining wall area and flying off of it near the ground level. In fact its probably a combination of all of the above, but you got a great video and managed to launch without boat mode from that heavy ole Ranger

 

[Bret]

Its a good looking cable cam ... minus the Ranger boat... (Im a Triton Guy) They are right about the curves and gps and such, but ive always noticed that going from land (the boat in this case) to water the barometric pressure seems to affect its accuracy. ive also experienced this when going from low to elevated land like over a retaining wall that has land behind it or being on a retaining wall area and flying off of it near the ground level. In fact its probably a combination of all of the above, but you got a great video and managed to launch without boat mode from that heavy ole Ranger

Hey Chris! Great to see a fellow fisherman on these boards! Triton, huh? Well, we'll just leave it at that! LOL Guess I learned one thing for sure, don't try fly too close to water. But still looking forward to getting some killer camera angles while fishing!

 

[RichWest]

But still looking forward to getting some killer camera angles while fishing!

Are you trying to be the next Darcizzle Offshore.....

 

[Bret]

Are you trying to be the next Darcizzle Offshore.....

Hah, I wish! I am not quite that good looking!!!!

 

[SARDG]

Are you trying to be the next Darcizzle Offshore.....

The offshore fishing boats look like mine - however... I do not look exactly like those fishermen. At least not for the last 30 years...

 

[RichWest]

LOL!!!!!!!!!!!!!!!!!!!! to both of y'all.

 

[quick_dry]

Interesting points about the bezier curve, I just flew a couple of cable cams over the house today so I'd have plenty of dips and easy height reference markers and speed didn't seem to impact on the path taken with respect to height.

I was seeing a few feet variance on runs just going back and forth, probably up to about 3 feet difference and this was running the cam slowly - but the wind was a little gusty so I'm guessing the baro was struggling.

 

[Bret]

Interesting points about the bezier curve, I just flew a couple of cable cams over the house today so I'd have plenty of dips and easy height reference markers and speed didn't seem to impact on the path taken with respect to height.

I was seeing a few feet variance on runs just going back and forth, probably up to about 3 feet difference and this was running the cam slowly - but the wind was a little gusty so I'm guessing the baro was struggling.

I can understand that. I have practiced many "dry " runs with a cable cam on land before even attempting this on water but I have never had the altitude drop like I saw on the water. In fact, I had posted earlier a similar video of a successful cable cam over water.

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[Deleted member 3203]

Thanks guys! As a newbie myself this was a very educational thread. Glad your Solo stayed dry Bret!

 

[MrNeill]

I got sweaty palms watching that!

 

[User Name]

Iwas seeing a few feet variance on runs just going back and forth, probably up to about 3 feet difference and this was running the cam slowly - but the wind was a little gusty so I'm guessing the baro was struggling.

You'll always see some variance in altitude and position, consumer GPS is intentionally limited in its accuracy. Like the barometer, holding a position can be very accurate because it's also referencing accelerometer data, but returning to a precise location can be off a bit.

When you're 30, 50, 100 or more feet in the air, this is usually totally inconsequential, but when the point you're trying to hit is only 4 or 5 feet over the ground/water, a variance of a few feet can be the difference between fishing for bass and fishing for your Solo!