International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
2. MEASUREMENTS 
A spectral measurement always follows the same scheme: 
l. Measurement of light source 
2. Measurement of cuvette 
3. Measurement of light source 
This sequence guarantees for the stability of the light source 
and the sensor. Measurements with a duration of several hours 
have shown a constant behavior of the system. 
2.1 Results of the reference measurement 
The first measurement of the holmium oxide cuvette showed 
the following results: (The figure of the spectral optical 
measurement is shown in Appendix A) 
  
  
  
  
  
  
EROR COMPRO Measured peaks Differences 
279 nm Not measurable Not measurable 
361 nm 362 nm - I nm 
453 nm 450 nm +3 nm 
536 nm 537 nm - 1 nm 
638 nm 639 nm - 1 nm 
  
  
  
  
  
Table 3: Absorption peaks of the holmium oxide cuvette 
The comparison between a priori known values and measured 
absorption peaks shows maximum deviations of approximately 
3 nm. This corresponds with the manufacturers information of 
the spectral resolution of the sensor so that the calibration 
which transforms sensor position into wavelengths can be 
accepted. 
Measured intensities have then been tested by using the neutral 
glass filters, tab. 4 and Appendix B. 
but a systematic offset of —0,014 is statistically significant. 
Nevertheless, considering this offset does not improve the 
derived spectral optical density data to a remarkable amount. 
2.2 Results of the repetition of the measurements 
During field work the instrument is subject to environmental 
strain of climate like temperature and humidity, vibration and 
others. So, after four months of use in laboratory and field work 
a review of the calibration of the sensor has been undertaken. In 
order to minimize error sources in the repetition the same fiber 
optics have been used in the same sequence as in the first 
measurement. 
  
  
  
  
  
  
  
  
  
Tueereed peaks Measured peaks Differences 
279 nm Not measurable Not measurable 
361 nm 359 nm + 2 nm 
453 nm 448 nm + 5 nm 
536 nm 537 nm - 1 nm 
638 nm 639 nm - 1 nm 
  
  
Table 5: Results of the holmium oxide cuvette after 4 months 
The results did not show significant differences to the previous 
measurements. The narrow banded absorption peaks of 
holmium oxide have been found again with differences in the 
order of magnitude of the spectral resolution of the sensor. 
Also, the systematic offset of the ordinate has been repeatedly 
determined with —0,016. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Measurements 
Wavelength n(F2) n(F3) n(F4) 
440 0,288 0,516 0,987 
465 0,260 0,476 0,928 
546 0,256 0,482 0,942 
590 0,269 0,508 0,977 
635 0,269 0,495 0,934 
Differences 
Wavelength n(F2) n(F3) n(F4) 
440 -0,020 -0,017 -0,023 
465 -0,023 -0,000 -0,029 
546 -0,018 -0,013 -0,016 
590 -0,014 -0,008 -0,017 
635 -0,014 -0,009 -0,019 
  
  
  
  
  
  
  
  
  
  
Measurements 
Wavelength n(F2) n(F3) n(F4) 
440 0,282 0,514 0,987 
465 0,255 0,474 0,923 
546 0,254 0,480 0,937 
590 0,268 0,506 0,072 
635 0,268 0,492 0,929 
Differences 
Wavelength n(F2) n(F3) n(F4) 
440 -0,014 -0,015 -0,023 
465 -0,018 -0,017 -0,024 
546 -0,016 -0,011 -0,011 
590 -0,013 -0,006 -0,012 
635 -0,013 -0,006 -0,014 
  
  
  
  
  
Table 4: Results of the neutral glass filters 
The results are convincing in the whole visible spectral range 
and they are in accordance with the manufacturers information 
90 
Table 6: Results of the neutral glass filters after 4 months 
2.3 Measurement of chlorophyll 
The reason for considering the concentration of chlorophyll in 
plants in a Phytoremediation project results from the influence 
of pollutants, e.g. heavy metals like lead or cadmium, on the 
production of specific kinds of chlorophyll in plants. Thus, 
chlorophyll can serve as an indicator for the occurrence of 
pollutants in soil and is expected to allow for the estimation of 
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