Height Webinar

General discussions of measurement techniques and the results of testing of techniques and equipment.

Moderators: edfrank, dbhguru

Post Reply
User avatar
dbhguru
Posts: 4528
Joined: Mon Mar 08, 2010 9:34 pm

Height Webinar

Post by dbhguru » Tue Jun 03, 2014 5:15 pm

Ents,

The AF-LTI webinar series has ended. Don and I gave #3 on height at 12:00-1:00PM earlier today. About 60 people signed up. More will view it when it is officially posted on the AF website in about a week. All three webinars will continue to be viewable through AF.

It is too early to tell what the overall impact of the three webinars will be in terms of garnering support for more advanced methods of tree measuring. However, Don and I will push on to help cement the working relationship between AF, LTI, and NTS. We'd like to add TCI to the mix to give us added depth in measuring. At least, that is the plan. We regret that Sheri Shannon will be leaving AF. She has been the driving force behind the progress made by AF in the past several years. Until Sheri came on board, AF operated the big tree program at the level of the lowest common denominator. However, thanks to Sheri, AF is now looking to push the envelope. We wish her the best in her pursuit of a new career path, and have our fingers crossed that her replacement will carry on in her footsteps.

After the webinar, Don and I discussed our shared priorities. Much remains to be done. One project is to explore the development of BASIC programs for iPhone and iPad to execute tree measuring calculations automatically. I'm exploring the use of Hot Paw Basic, an old fashion language interpreter that is easy to use. I plan to develop and test programs that cover all height, girth, and crown spread methods. Anyone with an iPhone 4 or later can participate. Hot Paw Basic only costs $1.99. It is a variation of Chipmunk Basic, a more sophisticated language interpreter - despite its friendly name.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

User avatar
Matt Markworth
Posts: 1302
Joined: Fri Nov 23, 2012 8:41 pm

Re: Height Webinar

Post by Matt Markworth » Tue Jun 03, 2014 8:29 pm

Bob, Don,

I thoroughly enjoyed the webinars and hope that those that couldn't make the live broadcasts will catch the videos when they come out.

I was impressed with how much material was covered in today's height webinar, and in such a clear and concise way. Cross-triangulation and the external baseline method were new for me, and the diagrams brought them to life. I especially like the explanation and diagrams that showed what can go wrong with the tangent method. Once the video goes up, I think it will be the definitive resource showing the range of height measurement techniques and the challenges that go with each. I also like Don's comments on some of the qualitative best practices, such as taking some time to get to know the form of the tree and the benefits of having two measurers working together.

I'm also looking forward to the day when more automation can be done with smartphones. I have an iPhone 4 and can help with testing programs in the field.

Matt

User avatar
tsharp
Posts: 419
Joined: Mon Mar 15, 2010 12:04 pm

Re: Height Webinar

Post by tsharp » Tue Jun 03, 2014 9:19 pm

Bob, Don:
Congratulations on putting together great presentations. I watched all three but still have not wrapped my head around the external baseline method.
If AF or anyone else maintains the access to these presentations it will have enormous impact on the quality of tree measurement in the coming years.

User avatar
dbhguru
Posts: 4528
Joined: Mon Mar 08, 2010 9:34 pm

Re: Height Webinar

Post by dbhguru » Wed Jun 04, 2014 1:20 pm

Turner,

With respect to the External Baseline Method for height, you can think of it this way. From a convenient location, you want to know the height of a target (top of a tree) above eye level. You can't determine the distance directly from eye to target (sine method), nor can you establish a baseline that extends from eye to a point vertically beneath the target (tangent method). However, if you can establish a short, level baseline in the direction of the target and take vertical angles to the target from each end of the baseline, you can compute the height of the target above eye level using the formula:
Screen shot 2014-06-04 at 2.05.02 PM.png
Screen shot 2014-06-04 at 2.05.02 PM.png (16.15 KiB) Viewed 1109 times


Here, A is the angle from the closer end of the baseline and B is the angle from the more distant end, and D is the length of the baseline The baseline must point in the direction of the target. Since three measurements are being used to compute the height of the target above the eye, the method is more sensitive to errors. It is a method of last resort, but it does work.

If the ground slopes so that the baseline slopes, the angle of slope must be determined. Then if C is the aslope angle of the baseline, the formula for height becomes:

Screen shot 2014-06-04 at 2.12.12 PM.png
Screen shot 2014-06-04 at 2.12.12 PM.png (16.93 KiB) Viewed 1109 times
I realize that these more involved formulas are cumbersome to use in the field. They can be put into a programmable calculator or used in a BASIC program loaded into the iPhone. You can also use an Excel spreadsheet, but most of us don't carry laptops into the field.

There are other ways to triangulate the top of a tree, such as the parallax method or the three-triangle method developed by Michael Taylor. I didn't address them in the webinar, nor did I cover breaking up the tree in sections, measuring the sections separately, and putting them together. I think a lot of people figure that one out for themselves.

The External Baseline Method for crown spread is a lot more involved. I'll speak to it in a future post.

Again, I would emphasize that the External Baseline Method are used as a last resort.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

User avatar
Matt Markworth
Posts: 1302
Joined: Fri Nov 23, 2012 8:41 pm

Re: Height Webinar

Post by Matt Markworth » Tue Jun 10, 2014 6:32 pm

All,

The Height Webinar recording has been uploaded to the LTI website:

http://www.lasertech.com/blogs/Professi ... binar.aspx

Matt

Post Reply

Return to “Measurement and Dendromorphometry”