The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
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3.3 Establishment of a regression model 
For the establishment of a regression model the correlation 
between the VI and agronomic parameter from the experiment 
field data from 2006 have been tested by coefficient of 
determination (R 2 ). Generally the correlations are dependent on 
the winter wheat variety and GS. For the analysis four different 
feekes GS (4, 5, 7 and 9) were used. The analysis show that 
correlations between hyperspectral Vis and agronomic 
parameters are higher as for multispectral Vis. Significant 
correlations could be made for biomass, N-content, N-uptake, 
SPAD and measured LAI for the experiment fields. N-uptake 
was calculated as the product from dry biomass and N-content. 
Biomass and plant N-uptake show the highest R 2 values for 
HNDVI, HVI, OSAVI and MCARI2 for the experiments fields. 
SPAD readings were only significant for the GS 4, but not for 
other GS or across all stages. The chlorophyll content decreases 
during the stages 4 to 9, so that this parameter is disregarded for 
the use in a model. The R 2 for LAI and the VI also show 
different significant and not significant correlations for the tree 
experiments. An establishment of a model for LAI is not 
possible with the 2006 data. 
Results for multispectral Vis like the NDVI in this study are 
evaluated in Li et al. (2008). Analysis from Koppe et al. (2008) 
show that Normalized Ratio Indices (NRI) derived from a large 
number of two-bands combinations of EO-1 ALI and Hyperion 
satellite images offer good results 
3.4 Model evaluation 
In this step the data are analysed for model evaluation. Thereby 
the data of the farmer's field from the two years 2006 and 2007 
are validated. For 2006 the GS 4, 5, 7 and 9 have been 
considered and for 2007 GS 4, 5 and 7. Table 2 shows the 
coefficient of determination (R 2 ) for the agronomic parameters 
like biomass, plant N-uptake and LAI and selected VI. Plant- 
uptake and biomass show the highest R 2 values for all Vis. 
HNDVI and OSAVI are more significant as NDVI and other VI 
for the four stages and across the stages in 2006. Correlations 
for LAI can be stated only for two feekes GS. Regarding the 
analysis of 2007, the performance of the regression models is 
less reliable than in the 2006 analysis as the R 2 values are lower. 
Especially the R 2 values for OSAVI at the feek GS 4 and 5 are 
lower as for RVI or NDVI. So in 2007 the models for RVI show 
the best performance for the feekes GS 4 and 5, OSAVI for the 
GS 7 and across all stages calculations of OSAVI and HNDVI 
provide best results 
NDVI 
RVI 
HNDVI 
HVI 
OSAVI 
MCARI2 
Feekes growth stage 4, n = 74 
biomass (kg/ha) 
0.629*** 
0.603*** 
0.665*** 
0.518*** 
0.656*** 
0.567*** 
Plant N-uptake (kg/ha) 
1 0.710*** 
0.707*** 
0.752*** 
0.716*** 
0.727*** 
0.532*** 
Feekes growth stage 5, n - 43 
biomass (kg/ha) 
1 0.323* 
0.323* 
0.318* 
0.160 
0.313* 
0.239* 
plant N-uptake (kg/ha) 
1 0.390** 
0.391** 
0.330* 
0.305* 
0.445** 
0.393** 
Feekes growth stage 7, n = 43 
biomass (kg/ha) 
0.107 
0.101 
0.123 
0.034 
0.115 
0.086 
VO 
o 
plant N-uptake (kg/ha) 
I 0.294* 
0.290* 
0.308* 
0.176 
0.357* 
0.304* 
o 
N 
LAI 
0.077 
0.081 
0.088 
0.193 
0.182 
0.222 
Feekes growth stage 9, n = 43 
biomass (kg/ha) 
1 0.104 
0.101 
0.126 
0.099 
0.156 
0.119 
plant N-uptake (kg/ha) 
0.130 
0.124 
0.129 
0.149 
0.202 
0.181 
LAI 
1 0.148 
0.152 
0.296* 
0.300** 
0.389** 
0.357** 
All growth stages n= 
203, n = 86 for LAI 
biomass (kg/ha) 
I 0.583** 
0.603** 
0.609** 
0.441** 
0.620** 
0.525** 
plant N-uptake (kg/ha) 
I 0.593** 
0.618** 
0.618** 
0.449** 
0.631** 
0.532** 
LAI 
1 0.114 
0.112 
0.149 
0.115 
0.239* 
0.203* 
Feekes growth stage 4, n = 95 
biomass (kg/ha) 
I 0.407*** 
0.443*** 
0.410*** 
0.054 
0.229** 
0.289** 
plant N-uptake (kg/ha) 
1 0.351*** 
0.333** 
0.349** 
0.082 
0.241** 
0.299** 
Feekes growth stage 5, n = 52 
biomass (kg/ha) 
H 0.323* 
0.358** 
0.342* 
0.151 
0.302* 
0.379** 
t" 
© 
plant N-uptake (kg/ha) 
0.390** 
0.301* 
0.292* 
0.111 
0.270** 
0.454** 
© 
fN 
Feekes growth stage 7, n — 50 
biomass (kg/ha) 
J 0.044 
0.037 
0.051 
0.101 
0.114 
0.131 
plant N-uptake (kg/ha) 
1 0.023 
0.013 
0.022 
0.031 
0.049 
0.138 
All growth stages, n = 197 
biomass (kg/ha) 
j 0.583** 
0.603** 
0.609** 
0.441** 
0.620** 
0.525** 
plant N-uptake (kg/ha) 
0.593** 
0.618** 
0.618** 
0.449** 
0.631** 
0.532** 
* significant at 0.05 level; ** significant at 0.01 level; *** significant at 0.001 level 
Table 2. Correlations coefficients for relationships between agronomic parameters and Vis for farmer’s field