Just wanted to give an update...

[ryandallas]

My fellow eNTS,

I've been posting more frequently lately, and my posts have included measurements from an instrument, a hypsometer, which I believed was accurate. However, I recently switched back to the old ProStaff + Clinometer combo, and it looks like the hypsometer might have been inflating some measurements. In keeping with the spirit of the NTS, I am going to remove data that I believe is exaggerated. The exaggerations were not way out there. Maybe in the neighborhood of 3-4 feet. Still, that is excessive for this group, so I will be removing some posts.

I just want to say that during my time as an Ent, I have never posted data with the intention to mislead, etc. All of the data I have posted, however accurate or inaccurate, was posted in good faith. To do otherwise would be to do a disservice to this organization.

I will be working with the administrators on this.

Take care,

Ryan

[dbhguru]

Ryan,

I will personally vouch for you. No need to explain further. BTw, what hypsometer were you using.

Bob

[ryandallas]

Thanks, Bob. That means a lot. Just a run down of some issues:

The Mt. Laurel TT (Fairfield) was 148' measured with Prostaff and clinometer, not 152' as I previously reported. So unfortunately Fairfield is no longer in the 150+ club.

The great Allens Meadows Tree, which is one of the most impressive specimens I know of, is not a contender for 160'. It is 155.4' tall. I previously put it down at 158'.

There are some other things I have to change, too.

[ElijahW]

Ryan,

Don’t get too down on yourself. You’re doing the right thing by repeating your measurements and noting differences in equipment performance. I’ve gone through the same process myself and shared some of my results on the BBS.

To get a better handle on the accuracy of your hypsometer and/or laser rangefinder, I would suggest calibrating them. Verifying angles can be a little tricky, but checking distances is pretty straightforward: compare the readings obtained from controlled laser shots to a reflective target to the target’s actual known distance. The last time I calibrated my Trupulse (a while ago now) I used a long measuring tape for distance and a Suunto clinometer to check the angle.

My Nikon 440 generally shot about a foot long, but was very reliable and easy to use. The Suunto clinometer is also a great product, especially when mounted on a tripod. What hypsometer were you using?

Elijah

[bbeduhn]

Ryan,
I used to have a Nikon 550 that jumped a yard when I moved it around the top of a tree. I had several reports with erroneous information. Like yours, it was only 2-4 feet but that matters, especially if you're measuring possible record trees. It happens. I simply remeasured and updated the posts.
Brian

[dbhguru]

Folks,

There are lots of issues around laser accuracy and instrument calibration and/or developing correction factors. As we would all likely recognize, each instrument has its own characteristics. If you've developed a correction factor and are satisfied with it, you still have the challenge of hitting the intended target, which we all recognize is difficult in a cluttered environment. This is true even with the gate feature of the Impulse 200LR and TruPulse 200X.

If you go beyond measuring heights into volume modeling, getting accurate distances to trunk targets is crucial. For trees with straight trunks, though they may lean, you can check on distance returns by projecting from lower trunk short where clarity is not an issue.

The attachments shows how to do a linear projection to get the distance from eye to a point higher on the trunk. This is mainly to check on a laser shot that you've already made. If anyone wants more details, let me know. As you may guess, I have this projection process built into an Excel worksheet.

Bob

[ryandallas]

Hey Brian,

Thanks for the feedback. I too had to remeasure, and I posted some of my new measurements. I've edited some of my posts in the Connecticut forum. That's why some of the comments seems out of place...but overall everything reads fine I think.