AbstractA hyperspectral line imaging system VTTVIS with a resolution of 1.8 mm2 (commercialised by Specim Ltd. Finland as Imspector V7) was able to predict the leaf chlorophyll concentration 30% and the leaf nitrogen concentration 38% more accurate than a hyperspectral non-imaging system with a lower resolution of 3.3*105 mm2 using the spectral range from 438-756 nm in winter wheat at 16 nitrogen levels provided no other plant stress was present. This improved performance using the VTTVIS was due to a two-band classification extracting relevant green leaf pixels using upper and lower thresholds for both R550 and the Normalised Difference between Green and Red (NDGR) [R550-R670]/[R550+R670] prior to estimating the mean reflectance spectra used in the prediction models. The optimal limits modelling leaf chlorophyll concentration and leaf nitrogen concentration were found separately.
Through a detailed theoretical description and based on ray tracing results of the dispersion Prism-Grating-Prism unit in the equipment, significant image distortion within both the spectral and spatial dimension of the hyperspectral image were proved. Further pattern noise in form of e.g. fixed pattern noise (FPN), lens vignetting, slit width variations, wavelength dependent PhotoResponse NonUniformity (PRNU), fringing patterns, and narrow band quantum efficiency response variation were shown to introduce significant bias in the sensitivity response of the VTTVIS. All known authors using PGP based systems have not described procedures for handling these systematic noise sources. Thus it is likely their published results are confounded with significant system bias. Fast calibration procedures under field conditions using the solar spectrum were developed and tested for spectral calibration with accuracy of ± 0.5 nm and for minimising system pattern noise. However due to limitations of the equipment, it was not possible to develop a comprehensive procedure for completely correcting these errors.
Articles not included in the electronic version
List of articles
The thesis consists of a synopsis, two reports, three publications either submitted or in preparation, and four proceeding papers. The nine publications should be weighted in the listed order of this Ph.D. study and will be referred to as I….IX. The nine publications are:
I. Jørgensen R.N. 2002. The VTTVIS line imaging spectrometer - Principles, Error sources, and Calibration. Risø Report. Risø-R-1302(EN). Risø National Laboratory, Roskilde, Denmark. 113 pp.
II. Jørgensen R.N., Hansen P.M., and Nielsen N.E. 2002. Comparative study on nitrogen and chlorophyll quantification of a winter wheat canopy using a hyperspectral non-imaging and a hyperspectral imaging system. In Prep.
III. Hansen P.M. and Jørgensen R.N. 2001. Exploratory study of winter wheat reflectance during vegetative growth using three-mode component analysis. International Journal of Remote Sensing. Submitted.
IV. Jørgensen R.N. and Rasmussen P. 2002. Development and Design of a Line Imaging Spectrometer Sampler (LISS) - A User Manual. Risø Report. Risø-R-1189(EN). Risø National Laboratory, Roskilde, Denmark. 31 pp.
V. Hansen P.M. and Jørgensen R.N. 2001. The RISØ CROPASSESSOR - An idea to a low-cost, robust, simple, and modular measuring device based on existing technology for monitoring the spatial field crop variation. Third European Conference on Precision Agriculture, June 18-20. G. Grenier and S. Blackmore. (Eds.) Montpellier, France:Agro Montpellier. 1:37-42
VI. Jørgensen J.R. and Jørgensen R.N. 2001. Implications of different nitrogen application strategies on grain yield and quality of wheat (Triticum aestivum L.). Precision Agriculture Journal - Special issue/s on the 3rd European Conference on Precision Agriculture. (Submitted)
VII. Jørgensen J.R. and Jørgensen R.N. 2001. Impact on grain quality when nitrogen is 'sensor applied' by the 'hydro precise system'. Third European Conference on Precision Agriculture, June 18-20. G. Grenier and S. Blackmore. (Eds.) Montpellier, France:Agro Montpellier. 2:929-934
VIII. Jørgensen R.N. and Jørgensen J. R. 2001. Design of a grain sampling device for combines equipped with a differential Global Positioning System (DGPS) and a yield meter. Third European Conference on Precision Agriculture, June 18-20. G. Grenier and S. Blackmore. (Eds.) Montpellier, France:Agro Montpellier. 2:809-814
IX. Haahr V., Jørgensen R.N., Jensen A., and Overgaard J. 1999. A method for optimal site-specific nitrogen fertilisation. In: Precision Agriculture ´99, edited by J. V. Stafford, Sheffield, Sheffield Academic Press Ltd, p. 709-718. |