Rangeland reflectance characteristics measured by aircraft and spacecraft sensors

Abstract

Rangeland vegetation and soil measurements were related to composite rangeland reflectance measurements from Landsat multi spectral scanners (MSS) and color infrared aerial photographs. Ground data and remote sensor measurements were acquired on six sample dates in three growing seasons from a rangeland study site in north central Texas. The potential for using a normalized infrared/red difference parameter for measuring rangeland vegetation or for monitoring vegetation conditions from satellite or aircraft was indicated. In assessing the relationships between scene components and composite scene reflectance, a sun angle related shadow influence, which generally has been ignored, was identified as being important. Results of this study also strongly suggest that quantitative assessment of vegetation conditions by remote sensing must account for weather related influences on reflectance. Individual Landsat MSS band values were strongly affected by factors influencing scene brightness, including the amount of shadow in the scene. A normalized red/infrared difference parameter, ND6 ('(Band 6 - Band 5) v (Band 6 + Band 5 )), was effective in adjusting for much of the variation in scene brightness. The ND6 parameter was more sensitive to variations in the functioning green biomass components of the scene than were individual spectral bands or the other vegetation indices evaluated. All of the vegetation indices that employed Band 6 were more closely related to the green plant component of the scene than those using Band 7.