Observing Tree Heights

Today I spent some time playing with the NASA GLOBE Oberver Android app. One of the features of this app is an AR tool for measuring the height of trees. It works like this: you position yourself where you can see both the base and the top of the tree. Then you look through your phone’s camera, tilting the phone to mark the base and the top of the tree. Finally, you pace off the distance from your first point of view to the base of the tree. The app then makes an estimate of the tree height.

I found the app yesterday and performed a couple of quick tree measurements before it got dark and today I wanted to see how repeatable the measures were. I decided I’d take several measurements of the topped Douglas Fir where we plan on installing our Starlink user terminal. I measured 5 times and 4 of those measures were within a few feet of each other while one was about 15 feet different. I’m going to assume I didn’t hold the phone in a steady position for the outlier and that the cluster of similar results is the actual height of the tree (as well as the app can measure.)

So, what did I learn. First I learned that with some care on how you hold the phone height steady, while tilting it to bring the bottom and then the top of the tree into view, you can get very repeatable results even from different distances from the tree. The second thing I learned is that this topped Doug fir is taller than I thought. My original estimates (using the “stick method”) was that the tree was just over 100 feet tall. The NASA GLOBE Observer app tells me the tree is about 140 feet tall.

And this presents a problem for my Starlink mount because the cable on the Starlink terminal is hard wired to the terminal and it’s only 100 feet long. I had previously experimented with extending the cable 100 feet with an inline coupler and the resistance was high enough that the terminal wasn’t getting the voltage it needed and was rebooting frequently. So, I changed plans and instead decided to move the power supply out to the base of the tree and extend the other cable, the ones that goes from the power supply to the router. But I can’t easily put the power supply 40 feet up in the tree so it looks like I am going to have to extend that cable 40 or 50 feet to reach the ground. I’m crossing my fingers that I don’t see the voltage drop problem with a 40-50 foot extension that I was seeing with a 100 foot extension.

The tree I’m talking about is the far left one in this photograph. (Click the photo to see the full picture.) A previous owner had it topped well before we moved here. I’m not sure why they did that, but it’s “just” a Doug fir and not a redwood so I don’t mind too much and I’m hopeful that the tree will prove to be a good mounting location for our Starlink terminal.

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