Nube question - How do you gauge if you are high enough just using the screen to just skim the top of a tree?

[Skyryder]

So lets say I want determine the height of a tall palm tree. Standing next the the tree, fly vertically until the top is in the center of the view finder. But how low does it need to be to just clear it? Bottom 1/3rd? Totally out of the viewfinder?

Palm trees are bushy at the top, you cant really tell from VLOS. I know, when in doubt, fly higher but that's not what I am trying to accomplish, I want to know what the actual hight of the tree is using the drone. Or any tall object for that matter. Lots of lamp posts in my neighborhood.

 

[thispilothere]

Start out with something lower and closer so you can see it and gauge where on the viewfinder the clearance tends to be, then apply to the taller objects and hope for the best.

 

[edfrombama]

Good afternoon to all-
If you fly your drone fairly close to the object in question- not too close, please- and then adjust the gimbal of the camera to make it at at the horizontal position, the top of the object will be either above the horizontal point- it's taller than your drone's present position or it will be lower than your drone's horizontal position- it's lower than the drone, Now, it's those "looks to be even" objects that are toughest to judge.
The drone will give a pretty accurate height of the object when they are level.

Hope this helps-

good day to all- Ed

 

[vindibona1]

Good afternoon to all-
If you fly your drone fairly close to the object in question- not too close, please- and then adjust the gimbal of the camera to make it at at the horizontal position, the top of the object will be either above the horizontal point- it's taller than your drone's present position or it will be lower than your drone's horizontal position- it's lower than the drone, Now, it's those "looks to be even" objects that are toughest to judge.
The drone will give a pretty accurate height of the object when they are level.

Hope this helps-

good day to all- Ed

I'm a little confused about what you mean exactly when you say "horizontal point". Would that be the lower 3rd of the view window, or would it be the center point? How close is close to make that judgement?

I think it's really hard to judge the height of an object right on the scene. What I've started doing is going to Google Earth Pro to scout where I'm going to be flying and find out the elevation of the launch point (in MSL) and then look for the highest points that I might be flying over. A little math tells me how much height I need to clear in AGL. In my area, a lot of places that I like to launch from for practices is around 611 ft MSL, so I know that the local hotel is 134 ft from launch point. Trees at a local lagoon are an incredible 93ft AGL (launch point).

 

[Rich QR]

Most drones have downward-looking sensors, which will cause the drone to rise up when an object is just below the drone. Find something like a picnic table and try to fly over it "just skimming the top" to see what I mean. Most drones won't let you just skim the top of an object.

So is the point to measure the height of the tree? Or are you trying to get as close to the top of the tree as possible for photographic reasons?

Either way, you'll learn what it takes by starting with lower objects, like lawn furniture or short bushes/hedges.

 

[Ty Pilot]

I'm a little confused about what you mean exactly when you say "horizontal point". Would that be the lower 3rd of the view window, or would it be the center point? How close is close to make that judgement?

I think what @edfrombama is alluding to is the fact that: if your camera is at the full up position - looking horizontally, the horizon will be dead in the center of the screen (assuming you can see the horizon), and anything below the horizon in the foreground is beneath camera level and anything that sticks above the horizon is higher than camera level.

In this way you don't need to be close or near an object to get an estimation of the height. I say estimation because the barometers in these drones are not one hundred percent accurate - however the line of sight between a camera, the horizon and any object in between is absolute.

 

[YVRGUY]

If you don’t or can’t use the screen to estimate height and you have time on your hand…not as much time as it would take to rescue a drone from a tree or on top of a building…then try this.

Just a safe sure.

 

[Rich QR]

I think what @edfrombama is alluding to is the fact that: if your camera is at the full up position - looking horizontally, the horizon will be dead in the center of the screen (assuming you can see the horizon), and anything below the horizon in the foreground is beneath camera level and anything that sticks above the horizon is higher than camera level.

Right, except that, in many drones, the "full up" position is substantially above looking horizontally. My Mavic Mini will point up to 30 degrees above horizontal, for example. But when I set it at 0 degrees, it works as you describe.

 

[dirkclod]

God lord guys if you fly straight up and can see over the highest
point than don’t go higher than that. If you fly beyond that your going to be BVLOS If you go father. Then you most likely will lose LOS and lose signal.

 

[Yorkshire_Pud]

With the camera horizontal I raise the drone until the tree top is centre screen then I look at the drone's indicated height. If the 'tree' is likely to be an RTH obstacle then the the RTH height is set 5m to 10m higher than that. It's not something where you wasn't close calls or want to "just clear" something.
Indicated height, excluding VPS height, is measured by a barometer and that measures air pressure, air pressure can change. So what might "just clear" at the start of a flight might 'just clip it' at the end of a flight.

 

[vindibona1]

With the camera horizontal I raise the drone until the tree top is centre screen then I look at the drone's indicated height. If the 'tree' is likely to be an RTH obstacle then the the RTH height is set 5m to 10m higher than that. It's not something where you wasn't close calls or want to "just clear" something.
Indicated height, excluding VPS height, is measured by a barometer and that measures air pressure, air pressure can change. So what might "just clear" at the start of a flight might 'just clip it' at the end of a flight.

Good thought. I don't want to be anywhere near a close call. All of my close calls and one crash was when I was flying low, trying to fly between trees. One time I wanted to jog to the left after passing a tree but hadn't realized I hadn't gone fully past it yet. That was a pretty good crash. Somehow I miraculously got my M2P to flip over, re-launch from the crash spot and fly home with one partially broken propeller. About a week or so I was flying between trees and suddenly a brand appeared from the left into my view screen. I stopped immediately and moved right as quickly as I could respond. I thought I was above tree level, but I guess not.

 

[Phantomrain.org]

So lets say I want determine the height of a tall palm tree. Standing next the the tree, fly vertically until the top is in the center of the view finder. But how low does it need to be to just clear it? Bottom 1/3rd? Totally out of the viewfinder?

Palm trees are bushy at the top, you cant really tell from VLOS. I know, when in doubt, fly higher but that's not what I am trying to accomplish, I want to know what the actual hight of the tree is using the drone. Or any tall object for that matter. Lots of lamp posts in my neighborhood.

First I would learn to fly about a 2 ft over the water , you will notice that this is tricky enough , but this will teach you quickly how far from the water is comfortable after 50 ft out .. let Say 3 Ft for the next couple hundred feet and what you will find is that you will be smart to in gradually keep lifting up as you go further out.

Now that you survived that Water Skimming , and gotten the feeling of being able to trust your drone or NOT !

Once you see how difficult it is on the water where you have perfect line of sight, that will determine quickly the skills and challenge and Vantage point needed to be successful at the Art of Skimming the Tree Tops .

Even with that training , you need a few things to Tree Top Fly , as it something we do a lot of .


Take notice to how the flight allows me to gain perspective of the trees before the attempt to fly over them.
You can do this same thing by flying next to the tree line and finding your incline over the top .

Once you learn that trick it will be much easier with some practice to do this.
Today of course we just race out over the top of the trees now as seen in other our other videos.

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Trust in your drone :
A good vantage point from which to see the drone .
A good vantage point to see clearly your distance from the Tree tops
A gradual incline up the further you go out.
Notes of how far you went before a gradual incline .

You might even consider getting the Rescue Jacket to save you from your mistakes.


Phatnomrain.org
Gear to fly in the Rain. Land on the Water.

 

[Paint Rock Drones]

I assume that you want the challenge of measuring the tree with your drone. But just in case you really have a need to determine the height of the tree, you can do it from the ground: Tree Height Measurement | Forestry

 

[pinzmann]

I turn on the grid lines. There usually is a center crosshair. If I want to check the height of the tallest utility pole around me, I’ll fly close to it and line up the crosshair with the top of the pole. Then I add a meter to my height. Off course I set my camera on 0 elevation. I suppose you test this on a small bush a couple meters off the ground.

 

[Skyryder]

Thanks for your suggestion guys. So being late at night cant fly right now, I found the simplest way to test this out. Without flying it inside the house, I powered up the drone, hit the default gimbal reset to 0, turned on the screen grid with rule of 3rs and hand held it as if it were flying over a flat top chair. What I discovered was as long as it's always in the lower third it will clean the obstacle within about 6 inches including accounting for a forward tilt if it were in flight.

The catch is the closer you get the to object the more it comes into frame. Also, with big flat objects, you have to account for perspective. So when I tried this experiment over a large flat table, just focusing on the front edge would have caused a collision, it would collide because the back part of the table is higher up in frame. So it's the far back edge or total outlined of the object one must use as the guide to keep in the lower 1/3 of the screen to just clear it. Your results may vary.

 

[cheddar-man]

So lets say I want determine the height of a tall palm tree. Standing next the the tree, fly vertically until the top is in the center of the view finder. But how low does it need to be to just clear it? Bottom 1/3rd? Totally out of the viewfinder?

Palm trees are bushy at the top, you cant really tell from VLOS. I know, when in doubt, fly higher but that's not what I am trying to accomplish, I want to know what the actual hight of the tree is using the drone. Or any tall object for that matter. Lots of lamp posts in my neighborhood.

Not exactly rocket science. Turn on the gridlines. Stand at the bottom of the tree and launch from there so that the baro is zero'd at that point. Fly up the tree until the grid centre is at the highest point of the tree and read the altitude, it's pretty accurate. Then add a few feet to make sure of clearance.

 

[Skyryder]

Question is how accurate is the reading the drone puts out on the fly app. Plus or Minus What?

 

[Dave Maine]

Note that the altitude measured by the drone above takeoff level is often in error by 10’s of feet, and is not particularly repeatable.

 

[HoozierDroneDaddy]

Keep in mind, you are measuring the height of the trees near you. As you fly away from your location, the ground level can change as well as heights of the trees.

 

[DavidT_ NZ]

So lets say I want determine the height of a tall palm tree. Standing next the the tree, fly vertically until the top is in the center of the view finder. But how low does it need to be to just clear it? Bottom 1/3rd? Totally out of the viewfinder?

Palm trees are bushy at the top, you cant really tell from VLOS. I know, when in doubt, fly higher but that's not what I am trying to accomplish, I want to know what the actual hight of the tree is using the drone. Or any tall object for that matter. Lots of lamp posts in my neighborhood.

There are some replies here that cover your enquiry but I have done what you are asking about on a 16 metre high Norfolk Pine tree at my home, using my Air 2; also around some 10 metre big fronded palms. Firstly, check that you have the gimbal up/down setting available on your Controller’s Fn button (set in the DJI Fly menu). Then as you fly your drone up at launch, do a calibration check by setting the gimbal to the horizontal position using the Fn button and physically check via the camera/screen as you rise up, say, next to your house roofing gutter, that the screen crosshairs align with the gutter when the camera/drone is adjacent and offset to it. Then simply fly up to the top of your tree and gauge the position/height above take off level, again using the crosshairs. (I think that I recall you can choose “crosshairs” in DJI Fly as your screen target. I haven’t changed my setting in 2 years.) I also use the Fn up/down capability a lot when flying around my house roof doing inspections so that I avoid TV aerials, chimney, nearby tree foliage etc. Seeing the horizontal with the crosshairs is an added safety factor - as well as the visuals. The Air 2 with good GPS satellite control is extremely stable, even in a fresh breeze. Use Tripod Mode when flying in close, so that nothing too exciting can jump out at you! And if you have concerns about proximity, my (Air 2) drone has its handy zoom capability when in video mode; that gets me in close, safely, too. Cheers and safe flying.