Table 4: Influence ( ) of the five most important spectral variables on the regression equation of each of the feature-based regression models of approach A.

Spectral datasetRank 1Rank 2Rank 3Rank 4Rank 5
[%]Variable [%]Variable [%]Variable [%]Variable [%]Variable

ASD spectral resolution(1) In situ field36.6 −24.0 −10.9 −6.0 −5.9
(2) Bare soil field30.5 −21.1 −8.4 8.0 −7.7
(3) Laboratory27.6 16.9 −14.1 −11.8 −9.0
(1) In situ field−23.7 21.8 −12.0 4.9 4.9
Iron oxides(2) Bare soil field−17.6 10.6 −10.4 9.9 9.8
(3) Laboratory29.2 −14.7 −10.3 6.7 −5.6
(1) In situ field29.3 −29.1 7.9 5.6 4.9
Clay(2) Bare soil field−26.4 23.2 7.8 7.7 7.5
(3) Laboratory−28.3 18.8 −12.4 12.0 7.5

HyMap spectral resolution(1) In situ field34.5 −20.8 −13.1 8.1 5.7ASAF2330
(2) Bare soil field30.4 −18.6 −12.0 9.3 7.4
(3) Laboratory21.3 −14.2 10.1 −7.6 −7.4
(1) In situ field−14.0 12.3 −10.4 8.8 7.9
Iron oxides(2) Bare soil field22.0 −16.7 9.5 −7.8 −7.3
(3) Laboratory18.9 −18.0 11.7 −8.3 −7.1
(1) In situ field24.4 −22.2 11.2 −6.6 −6.5
Clay(2) Bare soil field24.8 −21.7 11.8    7.7 −5.3
(3) Laboratory26.3 −21.2 −14.3 11.6 −6.2

Symbols: absorption features (AFs): : area, : maximum depth,    : wavelength of , : depth at wavelength position given in literature, ASAF: asymmetry factor. Hull features (HFs): : mean reflectance in interval, : slope in interval.