Mapping Tree Footprints - The American Surveyor

ichael Taylor, a resident of small-town Hyampom, California, has a very unique hobby. Taylor is a member of The Native Tree Society (NTS), an interest group which includes some of the most renowned forest researchers in the world

among its members. Known as “tree hunters,” Taylor and other NTS members are on a search for the largest, oldest, and most unique trees in the world. According to the NTS, tree hunters aren’t just looking for spectacular trees, they also “…bring back measurements, observations, and descriptions of the places they visit.” And this is where Taylor’s specialties lie.

Having co-discovered the tallest known tree in the world, a 379.3-feet-tall coast redwood now named “Hyperion,” as well as discovering the second and third tallest trees in the world, Taylor is well-known among the tree-hunting com-

munity. His largest project currently involves co-authoring Dendromorphometry–the Art and Science of Measuring Trees in the Field, a book all about tree measurement. Taylor is now evaluating the effectiveness of different systems for collecting various tree measurements, which will be included in the book.

In 2011, Taylor received a donated rugged handheld—the Archer Field PC®—from Juniper Systems. Taylor said of the Archer, “Upon first handling this little tank-like PDA, I got the impression I could leave it out in the woods for a year or two and it would still power up and work just fine if recovered.” Loaded onto the Archer was Laser Technology Inc.’s MapSmart Field Mapping Software, designed especially for ease-of-use. Taylor uses this system to map tree footprints and to generate 3D surface point clouds for tree volume determination

So just what is a tree footprint? Imagine if you could trace around the outside edge of the bottom of a tree trunk, right

Mapping Tree Footprints

Above: A graphical representation of how Laser Technology Inc.’s MapSmart survey system works with the Juniper Systems Archer Field PC.

>> By Christopher Bahr

Displayed with permission • The American Surveyor • Vol. 10 No. 11 • Copyright 2013 Cheves Media • www.Amerisurv.com

Tree hunters admire the vastness of a massive tree they found.


along the line where the trunk meets the ground, the resultant shape that would be drawn would be the tree’s footprint.

Take, for example, a former American Forests champion ponderosa pine known by the name of Bear Wallow. Taylor first collected data about the giant tree’s footprint by standing at various positions around the tree, and using a laser rangefinder (the Impulse 200 LR) to collect as many survey points around the base of the tree as possible from each position. He then imported the files from the Archer to an interactive program in Excel on his laptop, where the collected data points could be tilted and rotated in three dimensions.

For comparison purposes, Taylor also mapped the footprint of a much smaller oak tree behind his home as a test to see how well the Archer/MapSmart/Impulse 200 LR system would work on a smaller scale. With much less surface area than the huge ponderosa, the smaller oak tree provided much more opportunity for error, since each error in the footprint would show up more profoundly in the survey. Taylor’s logic in mapping the oak tree’s footprint was, “If I can map this irregular and tiny oak tree, I feel I can map any larger tree in the forest.” And he was pleasantly surprised. “The results were surprisingly good,” he said. “The survey itself was much faster than expected.”

The problem most people run into when surveying tree footprints is determining where the trunk ends and the ground starts. To overcome this problem Taylor used a prism and pole to project the survey to a more clearly defined position directly above the footprint point. This allowed him to

create a footprint in the same proportion and shape floating above the actual ground reference point.

Another issue that may arise when map-ping tree footprints is that there is a three and one-half inch off-set of scope to laser on the Impulse 200 LR. Taylor accounted for this difference by simply pointing the laser three and one-half inches above where he wanted to map a point.

To collect more measurements on the ponderosa, Taylor also used the system to create a 3D surface point cloud of the tree’s trunk in order to accurately deter-mine its volume. He did this by mapping over 2,500 data points on the surface of the trunk, and then imported the data into Excel on his laptop. Because this use was outside the sphere of the software’s intended use, he found that after collect-ing about 800 data points, the MapSmart software began to slow down, taking much longer to calculate each point. To work around this, he conducted three separate surveys and later merged the

Equipment used: ◾ Impulse 200 LR ◾ Trupulse 360B ◾ MapStar angle encoder with

quick-release tribrach adapter ◾ Turck interface cables with

RS-232 adapter & remote trigger ◾ Heavy-duty aluminum tripod

(for tribrach mount) with quick-adjust sliders

◾ Plumb bob ◾ Reference tags and ground spike ◾ 2 Seco thumb-release tripods ◾ 2 extra quick-release tribrach

adapters with plumb bob hooks ◾ Prism pole ◾ Seco Mini Prism & Leica 360

Degree Mini Prism ◾ Brackets and adapters for Archer

Field PC and Impulse 200 LR

Mike Taylor uses a quick-release adapter to place the centroid of the prism and the Impulse 200 LR in the same position.


data. This approach worked perfectly, and the resulting 3D surface point cloud is really quite remarkable.

Taylor’s work in evaluating the Archer/MapSmart/Impulse 200 LR system will be addressed in the upcom-ing book he is co-authoring and will help to influence the way many tree hunters collect tree measurements in the future. “I have not found a better set of tools for the job,” said Taylor. While his use of the system is unique, the data collection techniques he practiced are useful in many different applications. For the regular tree hunter, the system provides faster, more accurate measurements on the search for the largest, oldest, and most spectacular trees in the world.

Christopher Bahr is a technology writer in eastern Oregon, where he enjoys tinkering with electronics, kayaking, and cooking in his brick oven.

Above: The footprint of a tree is displayed in Microsoft® Excel.

The Old American Forests Champion Ponderosa stands 234 feet high, with a volume of 5,300 cubic feet.

Left: An oak tree’s surface point cloud is generated in Excel with the data collected using the Archer/MapSmart system. The point cloud is made up of six merged surveys, consisting of about 5,600 XYZ points.


Mapping Tree Footprints - The American Surveyor

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