Measuring Method

We selected Harvard forest, Howland forest and Bartlett forest to do our field work. In each forest,two sites, with an area of 100 m * 100m respectively, and 5 plots for each site, circle with 20m radius, were designed to collect the forest structure related variables (i.e.diameter at breast height(DBH), tree species, crown position) for each single tree. In addition, some sampled trees were selected for detailed measurement (e.g. crown depth and height to crown). Trees in each plot will be plotted using distance and beraring to tria ngulate tree positions to known positions.

Coincident to the ground truth data collection, Echidna data were collected for each plot. To evaluate the influence of varied beam divergence, At each plot, two scans were made with two beam divergence. For the purpose of reference, hemispherical photoes were taken at each plot. LAI-2000 was used to collect LAI value. These reference data shall subsequently be used to calibrate and validate the estimation of LAI based on EVI data.

The measured properties included:

1. EVI:

ECHIDNA Validation Instrument (EVI) records a full waveform of returns for each point on the hemisphere of the forest. The data can also be processed to expose various aspects of the forest structure. More details…

2. Tree spatial position:

  • Tree range and bearing relative the center of each plot: Which are measured using laser/sonic range finder.
  • Occlusion (visible, occluded and partial occluded): Which describe the location that whether the trees can be seen from the center of plot .

3. Inherent characteristics:

  • Tree height and Height to crown: Which are measured using laser/sonic range finder.
  • DBH (Diameter Breast Height): Which are measured using tape.
  • Tree Species: The mainly species in the forest are maple, white pine, oak, beach, birch, fir and so on. Crown position (dominant, codominant, intermediate and supress): Describe the position of the crowns (branches and foliage) of the trees in the stand.
  • Crown radius: Which describe the size and shape of the crown.