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Determine tree height from photo?

Started by kelLOGg, December 31, 2022, 01:07:36 PM

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kelLOGg

I have fork of a maple tree that is splitting from the main trunk and leaning towards my trailer shed. It is not a big fork (~12" dia) but it could do damage if it is long enough to hit the shed. The shed is 57 feet away and I made estimates of the log length by strapping a 10' 8" pine 1 x 1 to the tree, snapping a pic of the whole length of the leaner and ratioed based on the photo to get the length. I took a pic on opposite side of the leaner to get a second measurement to compare results. They didn't agree: one measurement gave 52' and the other gave 40' - a big difference. Even though they are less than the difference to the shed I am curious as to why such a big difference in the measurement. I know this is not a standard technique in forestry but it was so easy I gave it a go.
 
Does a camera (iPhone in my case) distort the photo and invalidate the results?
I included the crown of the leaner in the length calculation as best I could which was tricky trying to distinguish from neighboring trees but I am pretty confident I did OK there. If you don't have a New Years Eve party tonight print out a copy and make your own measurements. :D
Happy New Year in any event.



 

 

  

Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

clearcut

As you have discovered, accurately measuring tree height is challenging. Accurately measuring them from imagery has a number of issues. 

A photograph is not a map. The relative position of an object, say the top of a tree, on an image can be difficult to measure for a number of reasons. 

First, cameras gather light in a cone shape, focused on a spot on a light gathering chip. Objects tend to appear radially displaced from the center. Look at an aerial view of the Washington Monument to see an example. 

The specific shape of the lens can impact how the final image appears. Think of how a fisheye lens distorts images.

Next to consider, was the camera exactly in the same orientation in both images; which is doubtful. That will distort the image, especially features that are farther away. Tiny differences at the camera can make large changes at a distance. 

This article describes a method for accurately assessing tree height from a photo with a known reference.

Lastly I would recommend cutting the leaner and measuring it with a tape if you want to know its length. It is poorly attached to the main stem and is likely to fail soon. 

Carbon sequestered upon request.

kelLOGg

I thought I was getting into something deep. I will read your article and reassess my approach. The camera was certainly not at the same angle for both pics. In one pic I was trying to get more of the crown so it was at a different angle from the other. It may fall before I get back to it. Raining now. Thanks for the comprehensive response. 
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

Ljohnsaw

In the second photo, it looks like the leaner is leaning away from you.  Both pictures should be perpendicular to the leaner if you are trying to compare apples to apples.  If the top is further away, it will look shorter, closer will look taller.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

Skeans1

Try something like Arboreal Tree it's an app for height measurement.

Ljohnsaw

Do it the easy way if your ground is flat.  Stand at distance where you are looking up at the top with an angle of 45°.  Then pace it off to the trunk.  That's how tall it is.  Another way, stand at your house and look up at the top.  If it is less than a 45° angle, your good.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

btulloh

All you need is your axe handle or a stick. 

https://youtu.be/cDy5OjfMfZ8

This works really well for determining where the tip of the tree will land. No fancy equipment, apps, or math. 
HM126

Ianab

Quote from: btulloh on December 31, 2022, 03:56:17 PMll you need is your axe handle or a stick. 


If you use a stick, then you can poke it into the ground where you are standing. Use it as your aiming point for the cuts, and see how close you can get. ;)
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

thecfarm

Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

kelLOGg

I'm getting cold feet on cutting the leaner, regardless of height. I could cut it safely but I'm not sure it would fall. Today the sky is clearer and I can see more clearly that the crown of the leaner is already enmeshed more than I thought in the crown is of nearby trees which may support the leaner which is not very big to begin with. I am, after all, a serious hobby sawyer and not a logger so I may be out of my league on this. I guess I will call the big guys and pay the big bucks. >:(



 
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

dougtrr2

Never a bad idea to take the safer route.  Why is it, that we tend to start doing that more as we get older?

Doug in SW IA

Kodiakmac

Because, that had me in stitches, dougtrr2.  ;D :D
Robin Hood had it just about right:  as long as a man has family, friends, deer and beer...he needs very little government!
Kioti rx7320, Wallenstein fx110 winch, Echo CS510, Stihl MS362cm, Stihl 051AV, Wallenstein wx980  Mark 8:36

Nealm66

I started about 40 years ago helping my neighbor with his tree service and eventually we had a partnership. He said there was a way to hold a 16" stick at arms length and walk back until the tips of the stick matched the top and bottom of the tree. Well, we didn't have a measuring tape so I estimated by two hand lengths and a scosh. It worked! I've used it for many years and within 5' every time. Couldn't tell you the exact length of the stick or if my arms the appropriate length but I highly recommend practicing until you get it dialed in. Very handy!

Ianab

Quote from: Nealm66 on January 03, 2023, 12:12:32 AMCouldn't tell you the exact length of the stick or if my arms the appropriate length


Your arm is always the right length, no matter how long your arm is. That's the clever part. 

If the stick is as long as your arm, and you are holding it outstretched, you will be making a 45 deg triangle with it. If your arm is a bit shorter or longer it doesn't matter. Like you say, you can predict where the top will fall, close enough to impress most onlookers at least ;)
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

YellowHammer

I'm looking at the pics and think the other trees are supporting the fork from falling so looks like a true hang.  Which in this case is good because the fork trunk didn't fall.  It also looks fairly small, and probably not a thousand pounds or so?  

Why not throw a weight bag up into the upper fork, 2/3rds up then run a bull line up with a running bowline and attach the rope to vehicle or tractor and pull it off to the side fracturing it at the nearly severed fork? 

Or run a tag line up in addition to the bull rope and use the two to pull it off the hang and slowly let it down sideways? Basically like lowering sails down a masted ship, using the vertical tree as the mast? 

One of the best investments I've made over the years is a 3/4" inch non stretch arborist bull rope, rated for 6,000 lbs.  It's way overkill for this situation, but would work.  You wouldn't even need a chainsaw as bad as the fork is.  Setting the rope way up a tree of small to modest size, and hooked to something strong enough, it will pull a tree to the ground with such tremendous leverage.  

Many 45° speed squares with ruler also have a bubble level, Amazon (speed square bubble level) and on a right 45 triangle, both legs are equal.  So sight up at the tree along the 45 line while walking away insuring the base of the square is bubble horizontal, and when the top on the tree aligns with the 45° edge you are sighting down, the top of the tree is exactly the distance you have walked away from the tree, plus how high you are hold the speed square. It's extremely accurate with a vertical tree, and reasonably accurate with a leaner.  Google "triangle tree height estimation" method.  

Another is the pencil method where a pencil or similar skinny stick is held vertically with thumb and forefinger at the bottom of the stick to be used as pivot.  Back up until the base of the tree aligns with your thumb and forefinger and the top of the tree aligns with the tip of the pencil or similar stick.  So the pencil covers the tree trunk from top to bottom. 
 Then without moving your arm, rotate your fist and the pencil 90° to horizontal to the ground using your thumb and forefinger as a pivot and the pencil will duplicate how long the tree will be on the ground. 

Or use the yardstick method which can be done with any long skinny stick marked or not. Here a video in it.

https://www.youtube.com/watch?v=cDy5OjfMfZ8

Just thinking how I might try it. 


 
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

kelLOGg

I tried throwing a weighted small rope up and around a knot about 1/3 the way up but I couldn't get it up that high. If I could get it up I would have a couple of options; 1) pull the rope down and measure its length to the ground and compute the length from the trunk to where the rope was on the tree. Use that length estimate the length of the leaner. 2) tie a heavy rope to the small one and pull the large one up and pull the leaner down. (Done that successfully several times).  

I will look into the more geometric approaches you (YH) and others have described. Still considering options including letting the pros do it. $$
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

YellowHammer

Rope throwing is tough, but if you get one of these little jewels, you can reach 40 feet relatively easily with an underhand swing toss, and with an over the back granny toss the bag will go up into space.  The little leather bag is 16 oz and will deform to not get stuck in tree forks, the orange line is some slick, stiff line that throws great.  The key to any string throw is to use the 5 gallon bucket to coil the string in so it zips out full speed.

Here's my tree throwing kit.  The throw line and bag are made by Forester and doubles the height and ease better than the twine and a rock I used to use.   

  

 

Here is short clip of me pulling an oak back leaner from off my building, much as you are wanting to do.  if you look, you can see how high I got the throw line up the tree with a simple underhand toss, hang about 3 feet of line out of my hand, swing it around and let it go.  The string whips out of the bucket like it's attached to a rocket.

Pulling Down a Tall Back Leaning Tree #shorts - YouTube  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

kelLOGg

A 5 gallon bucket is the ticket. My rope snags twigs etc and can't get much height. I'll try it tomorrow.
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

Don P

We made something like this.
AIR CANNON to put rope in tree. - YouTube

Don't straddle the bucket.
That might shoulda gone under "dumb things"  :D

If you have access to a transit there are some tree height calcs in the toolbox

YellowHammer

Yes, the bucket is the key.  Actually, after throwing rocks a string for years, when I got the real kit, I overshot so far it was incredible.  Through the tree, through another, and the bag landed on the building.  It's actually kind of fun, because it will go way, way up there unless you have a tangle.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

Walnut Beast


wkf94025

I use my drone.  Pretty sure you know a guy who knows a guy...
Lucas 7-23 swing arm mill, DIY solar kilns (5k BF), Skidsteer T76 w/ log grapple, F350 Powerstroke CCSB 4x4, Big Tex 14LP and Diamond C LPX20 trailers, Stihl saws, Minimax CU300, various Powermatic, Laguna, Oneida, DeWalt, etc.  Focused on Doug Fir, Redwood, white and red oak, Claro walnut.

62oliver

From a bit of a distance, look at the tree with a framing square at arm's length.
Whatever height you get, measure same on the ground, gets you in the ballpark.
Husqvarna 266, Case 90xt, JD310C, TJ240E, 02 Duramax

kelLOGg

No pictures but the tree is down yesterday. (Tied up with hernia repair surgery). A neighbor had a team of 3 (2 guys and a woman) do tree work for him and he passed them on to me. An hour of rope throwing and 15 minutes of sawing and it was over. They were very skilled and working safely was their mantra. $300. I was very pleased and will use them again if needed.
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks

Jeff

We learned in scouts how to exactly measure the height of anything. You just need a sunny day.  Measure the shadow of something, like your scout buddy, measure the trees shadow.

Mutiply the height of the shadow by your buddies height, then divide by his shadows length. Do it in the middle of the day if you have a short tape measure. :)

Wallah.


Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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