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### Test of AF-NTS Excel workbook for crown spread

Posted: **Tue May 27, 2014 12:48 pm**

by **dbhguru**

Hi All,

Attached is a draft Excel workbook for the External Baseline Method for Crown Spread. It is meant to be a join American Forests-Native Tree Society product. Don and I would greatly appreciate the assistance of our fellow and lady Ents in giving this workbook a test run. Thanks in advance.

Bob

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Wed May 28, 2014 10:04 am**

by **Larry Tucei**

Bob- Looks good. Now that I have the TruPulse 360 I have the capibility to measured crown spead with the Missing Line function. Way cool!! Larry

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Sat May 31, 2014 11:12 am**

by **Matt Markworth**

Bob,

My test subject is this chinkapin oak, which measures 67.9' x 14'2" x 83'. So far, I've used the hypsometer tab of the spreadsheet and it works like a charm. I think the biggest variable that I'm introducing is my choice of baseline. My numbers are in the ballpark for max spread. I have another angle (90º to max spread), which I will go back to the tree to get (because I'm not happy with my original choice of external baseline).

Max spread measured by the traditional method of locating drip line and standing underneath of the tree: 83.1'

Max spread using my selected external baseline and the spreadsheet: 87.5'

- crown measurement.PNG (3.54 KiB) Viewed 1569 times

Red arrows indicate the edge of the crown from this angle.

Matt

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Sat May 31, 2014 11:26 am**

by **dbhguru**

Matt,

Thanks ever so much! This is just what we now need, i.e. NTS testing of automated processes that allow users to take field measurements and then do the calculations through programs we design. I also have a Basic program that can be installed in an iPhone that has Chipmunk Basic installed. Very convenient. For iPhone users with Chipmunk Basic, I could supply a good two dozen programs to do field calculations.

I've been told by AF that we should be able to devise other spreadsheet solutions to measurement problems and have the spreadsheets posted on (accessible through the American Forests website. I think that in time we could have a dozen or more computational routines out there for widespread use.

Thanks again for the testing.

Bob

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Sun Jun 01, 2014 11:35 am**

by **Don**

Matt-

Thanks for your testing of the external baseline method, and Bob's EXCELlent spreadsheet solution to cumbersome math!

If you don't mind my asking, could you go through your routine of measuring the crown, using the 'dripline approach'?

Thanks!

-Don

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Sun Jun 01, 2014 12:26 pm**

by **Matt Markworth**

Don,

Sure, my pleasure. Let me know if you have any additional best practices to these steps I'm using.

1) Walk around the tree at a distance far enough beyond the crown to determine if there is an obvious max spread.

2) Walk the drip line of the crown, while shooting to the base, to reveal the points on the drip line that extend out the farthest.

3) Go to one side of the apparent max spread and use a 90º reading from the clinometer to ensure positioning directly below that point. Place a marker on the ground.

4) Walk to the other side of the tree and find the point on the crown that extends the farthest. Use the clinometer again to ensure positioning directly below that point and either run a tape to the marker on the other side of the tree, or use the horizontal function on the Trupulse 200 to find the distance.

5) Walking under the tree at 90º to the max spread, find the longest spread that exists 90º to the max spread. Repeat steps 3 and 4 to take the measurement. Average the two measurements.

6) If the crown is very irregular, then the spoke method would be more appropriate.

Bob,

After laying out some examples on paper (substituting millimeters for feet), I now realize that the position of the baseline has little to do with the accuracy of the measurement. Rather, the accuracy of each of the four horizontal distances can have a fairly sizable impact on the final result.

Matt

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Sun Jun 01, 2014 8:33 pm**

by **Don**

Matt-

Thanks for the measuring routine narrative...what was in the back of my mind as I asked, was could there be 4' of wiggle room in your 'vertical estimation'...the clinometer works pretty well for that, and I suspect there's not much wiggle room there...

Re measurements of distance, you're using a laser rangefinder, or otherwise calculating horizontal distances? And your 'spread pairs' are 180 degrees off of each other (with tree's base in line?)?

I'm trying to figure out where errors might be...four feet difference in forty feet, when divided by 1/4 for AF formula isn't much. While the external baseline method wouldn't usually be the only measurement of crown spread, it'd be nice to know it's range of accuracy~how far away before distances, or more likely, angle measures becomes a factor...

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Sun Jun 01, 2014 9:28 pm**

by **Matt Markworth**

Don,

I'll reply in bold italics within your text for clarity:

Don wrote:Matt-

Thanks for the measuring routine narrative...what was in the back of my mind as I asked, was could there be 4' of wiggle room in your 'vertical estimation'...the clinometer works pretty well for that, and I suspect there's not much wiggle room there...

**I agree, not much wiggle room there. Thanks to Rand for showing me the trick of using a 90º reading on a clinometer or hypsometer to find the spot directly below a targeted point on the dripline.**
Re measurements of distance, you're using a laser rangefinder, or otherwise calculating horizontal distances? And your 'spread pairs' are 180 degrees off of each other (with tree's base in line?)?

**Yes, I'm using the horizontal distance function on the Trupulse 200 for this particular application. In the above post I'm only comparing the max spread axis to the results of the external baseline, so there isn't a spread pair.**
I'm trying to figure out where errors might be...four feet difference in forty feet, when divided by 1/4 for AF formula isn't much.

**I was shooting to dead twigs with my Trupulse 200, which prevented the unit from displaying in half feet or in tenths of a yard. The smallest unit I could measure in was whole feet. The Trupulse 200 gives a more repeatable number when shooting at leaves, but when shooting to just a twig the number can bounce around a little bit. I've included a hypothetical chart here that shows that if the one of the four measurement was off by 1ft, with the other three measurements remaining the same, then this would account for the 4ft difference in the external baseline measurement. I believe this is where the error lies. In this example, I hypothetically changed the S1 measurement to 128ft, instead of 127ft, which brings D down by 4ft, and matches the result from the drip line method.**
- crown hypo 1.PNG (3.48 KiB) Viewed 1530 times

While the external baseline method wouldn't usually be the only measurement of crown spread, it'd be nice to know it's range of accuracy~how far away before distances, or more likely, angle measures becomes a factor...

*I agree. I think it's a good way to be in the ballpark, but not close enough to use as a final measurement in most cases. The applications of measuring a crown when it extends over water and getting a quick crown measurement for an inaccessible tree are both very appealing.*

Matt

### Re: Test of AF-NTS Excel workbook for crown spread

Posted: **Mon Jun 02, 2014 11:36 am**

by **dbhguru**

Matt,

Yes, you are correct. The External Baseline Method serves best to give us a preliminary estimate or as a method of last resort. Methods that use three or more measurements to get a result tend to be more sensitive to error, and often by unpredictable magnitudes. I've attached a spreadsheet that you can use to explore errors by adjusting the drawing of the method by putting its Excel measurements into the green cells, errors to one or more of the measurements, and a scaling factor to bring the measurements up to field size. If you'd like more information on it, please let me know. I can talk you through it. It allows your to visually explore the method a little better by drawing the basic shape of the field situation, scale the Excel dimensions up and play what if games by introducing errors to the distances.

Bob