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VEGETATION - 2000

Lake Maggiore - Italy, 3-6 April 2000


Monitoring North American Grasslands Dynamics with VEGETATION

David J. Meyer *, Bradley K. Reed *, Bruce K Wylie *, Larry L. Tieszen +, Cullen R. Robbins *, Allison L. Scherff *
*Raytheon Systems Company, EROS Data Center, Sioux Falls, SD 57198, USA
+ U.S. Geological Survey, EROS Data Center, Sioux Falls, SD 57198, USA

No paper available

This report culminates a multi-year study of the utility of the Systeme pour l’Observation de la Terre (SPOT) Haute Resolution Visible Infra Rouge (HRVIR) and Vegetation instruments for multi-scale monitoring vegetation dynamics in the Great Plains of North America. The proposed study included :

  1. a simulation of the Vegetation viewing geometry, including pixel size variability,
  2. the use of Vegetation for monitoring biophysical parameters over grasslands,
  3. the use of Vegetation for monitoring seasonal dynamics within the grasslands, and
  4. the utility of having spectrally matched, simultaneously acquired multi-resolution images to study spatial scaling processes within the Great Plains.

The pre-launch study focused on the simulations, refinement of field validation techniques and development of seasonal and monitoring scaling strategies for the post-launch phase; the pre-launch work is described in a previous report.

The post-launch study proceeded with biophysical, seasonal dynamics and multi-scale mapping studies using the HRVIR and Vegetation data sets. The biophysical component includes the mapping of surface relationship developed between reflectance, leaf area index (LAI), fraction absorbed photosynthetically active radiation (fAPAR) and green biomass to the HRVIR scale, then onto the Vegetation scale. The surface scaling methodology involves developing relationships between reflectance and biophysics at a "quadrat" scale (~0.5 m2), using extended reflectance "grids" large enough to be seen by the HRVIR to distribute the relationships across areas representative of HRVIR pixels, estimating the biophysical parameters at the grids scale using geostatistical techniques, then correlating the geostatistical estimates with HRVIR pixels. The scaling from HRVIR to Vegetation is done on daily syntheses acquired simultaneously with the HRVIR, the multi-date syntheses are used to distribute the measurements over time. The seasonal dynamics component of the study focused exclusively on the 10-day synetheses, using seasonal metrics develop for the Advanced Very High Resolution Radiometer (AVHRR). The results of the dynamics component of the study with Vegetation are compared to results retrieved from AVHRR data.