Six Polar Derivative National Phenological Maps Used in Multivariate Clustering
- Julian Day of Start of Spring, Defined by Day Accumulating 15% of Total Area Under the NDVI Annual Profile.
- Julian Day of Center of the Growing Season, Defined by Day Accumulating 50% of Total Area Under the NDVI Annual Profile.
- Duration of the Growing Season, Defined by the Difference Between Day Accumulating 15% GPP and Day Accumulating 85% GPP
- Degree of Seasonality, Shown as the Magnitude of the Resultant NDVI Force Vector, or Radial Assymetry in the Polar Plot
- Mean NDVI During the Growing Season
- Standard Deviation of NDVI During the Growing Season
All 6 of these polar derivative maps are highly orthogonal; that is, they have little cross-correlation with each other - Each map carries unique and different information