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Overview - Equipment - Getting Started - Mapping - Crown - Heights - Other Data - Data Review

Sylvan Datalogger

Tree Mapping

First for a new plot you will need to provide some background information such as plot shape, size, unit of measurement (metic or english), field crew names, name of the plot an a text location description.

Mapping is one the central tasks of the Sylvan Datalogger program. By mapping we are referring to the the x, y, z locations of the the references points and the tree stem centers st the ground line. In the Sylvan Datalogger program we use polar coordinate to collect this information similar to standard surveying techniques. All mapped locations are stored and displayed in Cartesian coordinates.

Important Note: if you are using a magnetic compass based instrument be sure to set the current magnetic declination for your location before you start mapping. Fore current information on magnetic declination at you location please refer to the NOAA Estimate value of Magnetic Declination.

Reference points

In mapping a plot we start with a base reference point usually labeled x=0, y=0, z=0 (Cartesian coordinates) at the time of mapping. If you have a GPS on we attempt to make a x, y, z estimated for the reference point but be aware that this estimate contains error from several sources. The GPS estimate is quit accurate to with 30 meters (100 feet) in most cases but may be more accurate depending on methods and a conditions. For square plots the base reference point is usually in the southwest corner of the plot to avoid negative coordinates. For round plot the base reference point is usually in the center of the plot

Additional reference points can be added anywhere the field crew desires as needed. Reasons for additions references include tree hidden from the base reference point or points that the field crew want to document such as a photograph locations. All additional reference point are referenced from the base reference point is possible of a previously established reference point. Note that in chains of reference points errors in the first leg of the chain influence all subsequent point mapped from these reference points.

The procedure to collect a new location is to shoot a line from the a laser ranging device sitting on a tripod at know height (usually ~ 1.5 m or ~ 5 feet) above the point. The laser range finder is pointed at the base of the new reference point. The computer will collect the azimuth, horizontal distance and angle from the eye point of the reference point the the ground level of the new mapped point. Note that id the ground level is obscured by vegetation you can use a height pole to establish a offset point.

Mapping a reference point

Figure 1. Diagram to illustrate the mapping of a references point.

Tree centers

Tree center are mapped in a manner similar to mapping reference points. Usually for trees we capture the polar coordinates at breast height of the tree to be mapped. It is assumed that breast height is a known distance from the ground and were have a diameter measurement available at that location. The datalogger program adds the radius of the stem to the horizontal distance from the reference point to the tree. and the z value is breast height distance below the x, y point.

Tree numbers are assigned at the time of mapping. Trees are numbers as consequitive integers starting from 1 or the last existing tree number.

Mapping a tree

Figure 2. Diagram to illustrate the mapping a tree.

Once the trees are mapped and assigned a tree number, the other measurements can be performed in any order. Aslo in the repeat measurement context mappin does not need to be repeated on plot remeasurements, as trees are assumed not to move. Only new ingrowth tree will need to be mapped.

Mapping a tree

Figure 2. Screenshot of the Datalogger lite screen for entering this data.


Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License.

Author: Dr. David R. Larsen
Created: January 31, 2013
Last Updated: February 19, 2013