Effect of altitude, view angle and sun angle, view angle correction procedures, and the atmosphere on deduced vegetative indices

Michael J. Duggin; Gerald J. Kinn; J. K. Muller; S. Myeong; M. Yavuz; C. Florack; J. Walton

doi:10.1117/12.372644

7 December 1999 Effect of altitude, view angle and sun angle, view angle correction procedures, and the atmosphere on deduced vegetative indices

Michael J. Duggin, Gerald J. Kinn, J. K. Muller, S. Myeong, M. Yavuz, C. Florack, J. Walton

Author Affiliations +

Proceedings Volume 3751, Airborne Reconnaissance XXIII; (1999) https://doi.org/10.1117/12.372644
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1999, Denver, CO, United States

Abstract

In 1997 and in 1998, EMERGE obtained multi-altitude digital image data over several sites, including Oneida County Airport, using a calibrated Kodak DCS 460 CIR camera. This study was part of a larger study. During a graduate research project, we examined two multialtitude color infrared digital image sets: one was obtained under partly cloud-shadowed conditions, and the other was obtained an hour later, under cloud-free conditions. In each case, we analyzed the uncorrected images obtained at each altitude, as well as the same images corrected for the bandpass-dependent lens fall-off with field angle. The digital radiance obtained at each altitude over selected vegetation and over other targets was used to deduce the normalized difference vegetation index (NDVI). The digital radiance and the NDVI for both the raw and for the corrected images were plotted as a function of altitude. It was possible to see the impact of atmospheric differences between acquisitions, and to study the effects of lens fall-off correction, as well as the effects of cloud shadow and sun-ground-sensor geometry on the NDVI. We report only part of the study. The dependence of digital radiance and NDVI on radial distance from the image center, and on the radial distance times the sine and cosine of the azimuth of each region of interest with respect to the perpendicular to the solar plane are mentioned. However, these form a data set too large to include in its entirety here. In concurrent studies, described in these proceedings, we also analyzed multialtitude data over forest and over agricultural targets. We studied the effects of location of the site in the image, altitude and cloud shadow on contrast between scene elements. The reported results are based on one of only a very few multi-altitude studies and have implications for all other imaging sensors.

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Michael J. Duggin, Gerald J. Kinn, J. K. Muller, S. Myeong, M. Yavuz, C. Florack, and J. Walton "Effect of altitude, view angle and sun angle, view angle correction procedures, and the atmosphere on deduced vegetative indices", Proc. SPIE 3751, Airborne Reconnaissance XXIII, (7 December 1999); https://doi.org/10.1117/12.372644

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