How tall is a...

[jwmcgrath]

OK, the broader question... and yes I know I could google all this but what fun is that?!

How do YOU estimate the tallest obstacle between you and a safe Return to Home?

There are of course a million variables... but at the same time, when you look at a forest in a landscape shot, all the trees are pretty much the same height.

So what's the average height of a tree?

A building averages 10' per floor so it's fair to estimate that a 5 storey building is at least 50'.

But I have no idea how tall a water tower is... or football uprights on the high school field... or telephone poles or high voltage lines.

So what do you do? Do you line up in front of an object with the camera level and use FPV to estimate height?

Do you google the height of common obstacles? Are you a natural at estimating vertical height?

There are a lot of references to estimate length on the ground but not so many references for upright things...

 

[jwmcgrath]

For the record, I've done all of the above... used FPV for the uprights, googled water towers, estimated telephone poles...

I just know there are a lot of smart people on here and there has to be some pretty interesting perspectives!

 

[Guzziknight]

I'll usually fly above the tallest obstacle and go from there.

 

[jwmcgrath]

I'll usually fly above the tallest obstacle and go from there.

Ok, but here's my dad's farm... the three fields. So if you took off from the driveway, and go on a high speed run towards the second or third fields, how high would you estimate the tree line to be without stopping at it first?

 

[Fester]

I use the camera view (set level) and the altimeter display to get tree heights, then add 50-75' as a buffer. Same for trees farther away. I set my initial altitude to say 200' here the fly in step fashion to determine the altitude of the tallest trees at my farthest destination waypoint.

 

[jwmcgrath]

...then add 50-75' as a buffer.

Seems reasonable. I was doing the same, using the camera at level, but I'm waiting to see if there are any botanist/pilots out there that can say the average height of a tree in the North Eastern hemisphere is X...

And I'm primarily curious because using maximum RTH values uses a lot of battery.

Also, another primary curiosity is high tension lines.

 

[Fester]

And then Murphy's Law will kick in and tree "Y", a close relative of Charlie Brown's "kite eating tree" will act like the worlds tallest Venus Fly Trap and swallow your precious bird . As to high tension lines your local power company might have someone to help you. My personal view is to avoid them altogether. Depending on weather conditions and operating voltage (some can operate at 500KV +), they are giving off corona discharges and small leakage arcs which also generate RF. I wouldn't think into the ghz range, but nonetheless...

 

[jwmcgrath]

True, and without even thinking about it I just threw high tension lines in there while I was thinking about "tall things", but I wouldn't fly near them anyway. The expectation is there would be wicked interference.

Fully agreed on Charlie Brown's tree!

 

[Fester]

Ok, but here's my dad's farm... the three fields. So if you took off from the driveway, and go on a high speed run towards the second or third fields, how high would you estimate the tree line to be without stopping at it first?

If you couldn't do it from using your bird and camera with the altimeter to get it, you'd have to look at it the way the Photo Recon folks do it...know the time of day, shadow length, and lots of Trig. to work it out. Looks like the sun angle was very low here, and otherwise don't ask me. Trig., Algebra etc give me the willies.

 

[Richard R]

If you can see the whole tree, use the old boyscout trick. Hold a stick out at arms length and while sighting along it, adjust the length until it matches the apparent length(I.e. the height). Then rotate the stick parallel to the ground and note where on the ground matches up with the end of the stick. Then just walk off the distance from the tree to that point. That's the height of the tree

 

[jlcinga]

Position yourself so your arm held at 45 degrees points to the top of the object...your distance from the base of the object is equal to the height of the object.

 

[jwmcgrath]

Position yourself so your arm held at 45 degrees points to the top of the object...your distance from the base of the object is equal to the height of the object.

Smart! [emoji16]

 

[FlashBuddy]

I went through the same unease at not knowing exactly how high I should fly to avoid all objects in or near my flight path. One particularly Tall Tree in an area I fly, I flew the Drone to the top of the tree so I could look down on it from ten or twenty feet or so above - looked at my altimeter and that was about the height of the tree. As the months wind along, I gained an understanding generally how high I need to be relative to the objects around me. Bottom line for me is experience will give you the tools you need to feel confident around tall obstacles.