1.1.1. Product Description
One of the most important advantages of low-altitude remote sensing is that vegetation signals can be spatially filtered from other signals in the field (i.e. individual plant leaves can be resolved from the background). This enables advanced data products like individual plant counting and sizing, as well as much improved measurement sensitivity and accuracy over higher altitude aircraft or satellite measurements.
VF provides a measure of how much area within a plot is covered by vegetation as a fraction of total plot area (also referred to as canopy closure) – a good proxy for growth stage and relative biomass. This derives from the ability to spatially segment growing vegetation from background non-vegetation signals by exploiting the relative differences in light absorption characteristics. It is important to note therefore, that this capability deteriorates as plants begin to senesce and the leaf absorptive properties decrease with decreasing pigment concentrations.
Figure 5 below shows an example of SlantRange’s spatial filtering technique as applied to multiple wheat plots at tillering which segments growing vegetation from the background soil and other materials in the field.
Figure 5: Color image of wheat plots at tillering stage (left) and with the soil background filtered out of the image (right)
VF shares some similarities with EF, however EF is less sensitive to the size of the plants and more sensitive to the number of plants, where VF is influenced equally by the size and number of plants in the field. Figure 5 below shows two wheat plots with similar emergence fractions but different vegetation fractions.
Figure 6: Comparison of two wheat plots with similar emergence fractions and different vegetation fractions
1.1.2. Reporting Method
Fractional area coverage by crop species (0 – 1) over selected grid size