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### Re: New to site- Could have record white pine

Posted: **Fri Jul 25, 2014 1:42 pm**

by **Will Blozan**

The angle or instrument o measure is not the key issue with getting an accurate height. Please review and apply our measurement protocols and greatly extend you baseline to 200' or more.

Good luck and I look forward to more details!

Will

### Re: New to site- Could have record white pine

Posted: **Fri Jul 25, 2014 8:51 pm**

by **dbhguru**

Hi All,

This may be an example of what happens when we have a short baseline for a relatively tall tree with a broad crown. At 80 feet from the trunk, the odds of seeing the true top of the pine are low. We will most likely be looking at the end of an upturned limb that sticks out in our direction. The horizontal distance from the trunk to the tip of the upturned limb could be as much as 20 feet. Suppose it is in the cited case. The actual baseline to the target would then be 60 feet, which leads to a target height of 128.7 feet above eye level. Had the baseline to the trunk been 200 feet, the angle to the target would have been 35.4 degrees (assuming level ground). Then the computed height would have been tan(35.4) x 200 = 143.1 feet. That is still high, but well below the 171.

For a baseline distance to the trunk of 250 feet, the angle to the target would be 29.2 degrees and the computed height above eye level would be 139.7 feet. That's still 11 feet high, but coming down. Obviously, the error drops as the angle drops. At some point, getting back farther becomes impractical or impossible, but as a general rule of thumb, for tangent based calculations, the measurer should try to get the angle to below 45 degrees to minimize the impact of angle errors. Crown point cross-triangulation is the solution for crown-to-base horizontal offsets, the biggest source of errors.

It is obviously a big pine. If the trunk circumference is say 13 feet and, giving the tree the benefits of the doubt at 130 feet, we could have a trunk volume of around 725 ft^3. Adding limb volume, the total could be around 800 cubes. That would be a worthy white pine to document.

Bob

### Re: New to site- Could have record white pine

Posted: **Fri Jul 25, 2014 11:18 pm**

by **Haliotis**

Thanks to all for your help and info. I would have tried to measure from a greater distance if there was a clear sight line to the base. Now that I have a better understanding of the protocols explained on this web site, I should be able to put a couple of measurements together for a more accurate estimate.

### Re: New to site- Could have record white pine

Posted: **Sat Jul 26, 2014 5:43 pm**

by **dbhguru**

A potential solution to a tree with a hidden base, is to measure it in sections. From a closer vantage point where the base up to say the first major branch can be seen, that section can be measured. From a more distant vantage point, where the section from the limb to the top can be seen, the upper section can be measured and added to the lower section.

Measuring the upper section can be done by using the External Baseline Method separately for the limb and the top and then subtracting the limb height from the top height. The advantage of using the External Baseline Method is that it isn't subject to crown-to-base horizontal offset errors.

The External Baseline Method is explained in the Measurement and Dendromorphometry section. If you really get bitten by the measuring bug, a laser rangefinder would be a fine addition to your equipment repertoire. A laser and clinometer combination provides a way to achieve accuracy without too much calculating.

Bob