Submitted to: International Geoscience and Remote Sensing Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 8, 2001
Publication Date: N/A
Interpretive Summary: Many advances in remote sensing technology have been made recently in understanding signals of light and heat from plant leaves and soil. These signals can be used to obtain useful information such as water status and fertilizer needs. A major difficulty in applying these advances has been separating the signal of the plant canopy from the signal of the soil when both are present, which is often the case. We present a method for extracting the desired information from mixed targets by using a second signal that measures the relative proportion of soil and plant canopy present. Examples using the method include measurement of water evaporation over large areas; chlorophyll content of leaves, which is useful for precise application of fertilizer; and soil moisture using combined radar and optical wavelengths. Such indices will, when fully developed, be of great use to farm and rangeland managers for directing and conserving resources.
A method is presented that reduces the difficulty of measuring a particular quality of one component in a multi-component element. The Planar Domain Index design requires two measurements: that of a signal sensitive to the desired quality of the target component and another signal sensitive to the component's weight or relative proportion to the whole. The quality signal and component weight signal form the two dimensions of a plane, and the maximum and minimum possible values for each signal define the boundaries of a domain within this plane. The position of a coordinate pair within the domain can then be correlated to the quality being measured, independent of the component's proportion to the whole. Examples given involve mixed vegetation and soil targets, with vegetation indices used to measure the component weight. Quality signals of the example applications include canopy minus air temperature as a measure of evapotranspiration, a normalized difference of near infrared and far red wavelengths as a measure of chlorophyll content, and differential Synthetic Aperture Radar (SAR) for measuring near- surface soil moisture.