title: Improved Accuracy of the Asymmetric Second-Order Vegetation Isoline Equation over the RED-NIR Reflectance Space.
abstract: The relationship between two reflectances of different bands is often encountered in cross calibration and parameter retrievals from remotely-sensed data. The asymmetric-order vegetation isoline is one such relationship, derived previously, where truncation error was reduced from the first-order approximated isoline by including a second-order term. This study introduces a technique for optimizing the magnitude of the second-order term and further improving the isoline equation's accuracy while maintaining the simplicity of the derived formulation. A single constant factor was introduced into the formulation to adjust the second-order term. This factor was optimized by simulating canopy radiative transfer. Numerical experiments revealed that the errors in the optimized asymmetric isoline were reduced in magnitude to nearly 1/25 of the errors obtained from the first-order vegetation isoline equation, and to nearly one-fifth of the error obtained from the non-optimized asymmetric isoline equation. The errors in the optimized asymmetric isoline were compared with the magnitudes of the signal-to-noise ratio (SNR) estimates reported for four specific sensors aboard four Earth observation satellites. These results indicated that the error in the asymmetric isoline could be reduced to the level of the SNR by adjusting a single factor.
authors.affiliation: Department of Information Science and Technology, Aichi Prefectural University, 1522-3 Ibara, Nagakute, Aichi 480-1198, Japan. id151003@cis.aichi-pu.ac.jp.
authors.forename: Munenori
authors.initials: M
authors.lastname: Miura
authors.affiliation: National Institute of Advanced Industrial Science and Technology, The Institute of Geology and Geoinformation, Central 7, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8567, Japan. kenta.obata@aist.go.jp.
authors.forename: Kenta
authors.initials: K
authors.lastname: Obata
authors.affiliation: Department of Information Science and Technology, Aichi Prefectural University, 1522-3 Ibara, Nagakute, Aichi 480-1198, Japan. id151002@cis.aichi-pu.ac.jp.
authors.forename: Kenta
authors.initials: K
authors.lastname: Taniguchi
authors.affiliation: Department of Information Science and Technology, Aichi Prefectural University, 1522-3 Ibara, Nagakute, Aichi 480-1198, Japan. yoshioka@ist.aichi-pu.ac.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yoshioka
keywords: asymmetric; canopy RT model; cross calibration; inter-band relationship; inversion; leaf area index (LAI); vegetation isoline