Laser Remote Sensing of Vegetation Cover Using Reflection Coefficients Measurement Data

Abstract

One of the promising applications of laser remote sensing is a remote control of the vegetation cover. Adverse external factors, lack of fertilizers, and pollution lead to the inability of the normal development of plants. To provide a visual control of such conditions of the vegetation cover at the early stages is often difficult. For this reason it is a relevant task to develop the remote sensing systems to detect plant stress conditions as the indicators of an insufficient nutrient level, pollutants available in the soil, etc. An effective method of remote control of the vegetation conditions is that of laser-induced fluorescence. However, the laser fluorescent method of control has a drawback: for the majority of fluorescent lidars due to small value of the fluorescence cross sections an attainable range of the confident detection of fluorescence signal today is of 100-150 m. Therefore, the relevant objective is to integrate the fluorescent lidar with other optical range equipment that enables remote sensing of vegetation condition from an aircraft at an altitude of several kilometers (with high altitude of flight the scanning equipment provides sensing a greater bandwidth on the earth's surface). The paper analyses the laser remote system capabilities for sensing the vegetation conditions using the measurement data of vegetation reflection coefficients at various wavelengths. It shows that the laser remote sensing system is capable to control vegetation at two radiation wavelengths - one in the visible spectral range (for example, 0.532 mm), and the other - in the near infrared spectral range (e.g. 0.8 ... 0.9 mm). A potential delivery aircraft altitude for the active remote sensing system of vegetation conditions is estimated using the measurements of vegetation reflection coefficients. It is shown that for the wavelength of 0.532 μm in the visible range the limit height of sensing (with realistically attainable now hardware parameters) is about 4 km. For the wavelength of 0.8 ... 0.9 μm in the near infrared range (with the same laser pulse power source) the limit sensing height is higher (in the infrared range the reflection coefficient of vegetation is higher).