Locating field plots
Field data collection crews typically locate field plots using street maps indicating plot location.
Aerial photographs help pin down the plot center location. Plot center may fall in public land,
private land, or on the border of different land ownerships and land-use types. Plot center may be
permanently located by recording distance and direction from man-made features such as buildings,
telephone or light poles, street corners, etc. A photo taken of plot center can help relocate the
plot in the future. Permanent records of plot locations are important for assessing forest change
(e.g., tree mortality).
Global Positioning System (GPS) units can also be used for locating plot centers if the unique
coordinates of the plot center are known. But taking GPS readings can slow data collection if
satellite communications are slow or temporarily unavailable, or if there is heavy canopy cover, which
can potentially block communication signals from satellites. GPS units can also be expensive to rent
or buy. They are best used where no man-made features are readily available to relocate plots.
Following the protocol
Because the accuracy of the results of a UFORE project depend upon quality data
inputs, accurate field data collection is essential. Detailed criteria for each
datum can be found in the Manual.
This information can be loaded on a
PDA to be
taken into the field by using a program such as
Dataviz's
Documents-to-Go* or
Adobe's Acrobat
Reader* for Palm OS. The data collection crew will
require careful training and oversight to ensure accurate data collection.
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Quality control
In sampling projects, UFORE relies upon a relatively small amount of plot and field
data to estimate or "scale-up" to the
structure and functions of the whole urban forest of the area being sampled.
Therefore, errors in field data collection can have significant impacts on the
estimates obtained from UFORE as the errors are magnified in the final results.
To obtain the most reliable and accurate results from a UFORE project, it is
recommended that a quality control system be used. Such a system normally examines two
different areas:
- Field measurements
Checks on field data collection are made by re-sampling field plots after the data
have been collected. Quality control should be conducted throughout a UFORE
project, but is particularly important at the start of a project to ensure that all
data collection personnel are trained and using consistent and accurate data
collection methods (see Manual).
- Data integrity and coherency
Quality control is also useful after field data have been uploaded or entered into a personal
computer. Data checks can find errors such as numbers that are out of range (e.g. stem diameters
greater than normally encountered for a species), missing variables, or inappropriate measures
(e.g., crown width = 0 for live trees)
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