Section for FAQs regarding i-Tree Eco (UFORE)
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Field measurement data from randomly located plots (i.e. tree species, diameter, etc) are extrapolated upward for the entire study area. How does Eco do this statistical extrapolation? Does it consider the aerial image of the study area? What are the specific methods used for the extrapolation?
i-Tree Eco uses plot-based stratified sampling statistics. It does not rely on any remotely sensed data. In essence it calculates the values of interest per unit area from each plot (e.g. trees per acre). It then averages those values to come up with an estimate for each stratum by averaging those plots values. Stratum totals are then determined by multiplying the per area averages by the area of the stratum. Stratum totals can then be combined to come up with study area estimates. For a more detailed formula based explanation of this procedure please see this item on our methods webpage:
For additional detail about i-Tree Eco methods please see the i-Tree Eco Methods page and the new Understanding i-Tree document.Stratified Sampling Statistics
Stratified sampling statistics used in i-Tree Eco plot-sample type projects - i-Tree Eco plot-sample type projects use traditional stratified sampling statistics that are summarized in many places on the web and taught in most introductory statistics courses. This document describes how those methods are implemented in i-Tree Eco to expand plot samples into stratum and population level estimates. These estimates include sampling variance and standard error which capture sampling error associated with measuring a portion of the population (i.e the plots) to represent of the whole population.
A member of the i-Tree Team