Prof. Dr. Ing. Wouter Verhoef
ITC
Dept. of Water Resources (WRS)
P.O. Box 6, 7500 AA Enschede
The Netherlands

Tel: +31 (0) 53 4874289
Fax: +31 (0) 53 4874400
Email: verhoef (at) itc.nl
Website: http://www.itc.nl/about_itc/resumes/verhoef.aspx

Background

Dr. Wout Verhoef  has been employed in remote sensing since 1973. Until 1977 he worked at NIWARS, Delft, in a research programme involving measurement and interpretation of spectral reflectance signatures of crops, soils and waters. In 1977 he joined NLR, where he developed the well-known SAIL vegetation canopy reflectance model (1981). This was followed by other optical models, such as a simple atmospheric scattering model to be used for atmospheric correction, the forest light interaction model FLIM, a canopy fluorescence model and a more advanced generic N+2-stream method for accurate modelling of radiative transfer in the atmosphere as well as leaf canopies. Among other subjects related to radiative transfer modelling, the N+2 stream method is presented in his PhD dissertation, which he defended at Wageningen University in 1998.

Other of his interests are in image processing of optical remote sensing data. The HANTS algorithm was developed for the temporal analysis of time series of images. A multichannel image segmentation method based on hierarchical edge detection and region formation has been developed to exploit spectral as well as spatial coherence. A cascaded pairwise principal components analysis (PPCA) algorithm, using advanced lifting techniques, was proposed to ESA and applied successfully to data compression of hyperspectral images. Recent activities in radiative transfer modelling have resulted into powerful image simulation software based on the integrated soil-leaf-canopy model called SLC and the so-called four-stream concept. Coupled to effective parameters describing radiative transfer in the atmosphere derived from MODTRAN4 model outputs, this provides a very effective and realistic solution to simulating hyperspectral multi-directional missions. Wout Verhoef has participated in several ESA studies related to the candidate Earth Explorer Mission SPECTRA. Here image simulation and biophysical parameter retrieval by model inversion were the prime topics of investigation.

In relation to China there are very fruitful relationships with Prof. Dr. Bob Su of ITC and with Dr. Li Jia of Alterra in Wageningen. Wout Verhoef is a regular reviewer of manuscripts submitted for the journals Remote Sensing of Environment and International Journal of Remote Sensing.

Wout Verhoef has no teaching experience, but he has coached several students at NLR during their traineeships, and conveying technical-scientific information to people in presentations has his special interest.

Peer-reviewed articles

W. Verhoef, 1984, "Light scattering by leaf layers with application to canopy reflectance modeling : The SAIL model", NLR MP 84011 U / Rem. Sens. of Env. 16:125-141.

W. Verhoef, 1985, "Earth observation modeling based on layer scattering matrices", NLR MP 84015 U / Rem. Sens. of Env. 17:165-178 (1985).

A. Rosema, W. Verhoef, J. Schroote and J.F.H. Snel, 1991, "Simulating fluorescence light-canopy interaction in support of laser-induced fluorescence measurements", Rem. Sens. of Env. 37:117-130.

A. Rosema, W. Verhoef, H. Noorbergen and J. J. Borgesius, 1992, "A new forest light interaction model in support of forest monitoring", Rem. Sens. of Env. 42: 23-41.

M. Menenti, S. Azzali, W. Verhoef and R. van Swol, 1993, "Mapping agro-ecological zones and time lag in vegetation growth by means of Fourier analysis of time series of NDVI images", Adv. Space Research, 13, 233-237.

J.G.P.W. Clevers, H.J.C. van Leeuwen and W. Verhoef, 1994, "Estimating the fraction APAR by means of Vegetation Indices: a sensitivity analysis with a combined PROSPECT-SAIL model", Rem. Sens. Reviews, Vol. 9, pp. 203-220.

W. Verhoef, M. Menenti and S. Azzali, 1996, "A colour composite of NOAA-AVHRR-NDVI based on time series analysis (1981-1992)", Cover Article, Int. Journ. Rem. Sens., Vol. 17, no. 2, 231-235.

W. Verhoef, H. Bach, 2003, "Remote sensing data assimilation using coupled radiative transfer models", Physics and Chemistry of the Earth 28, pp. 3-13.

W. Verhoef and H. Bach, 2003, "Simulation of hyperspectral and directional radiance images using coupled biophysical and atmospheric radiative transfer models", Rem. Sens. of Env. 87: 23-41.

B. Pinty, J.-L. Widlowski, M. Taberner, N. Gobron, M.M. Verstraete, M. Disney, F. Gascon, J.-P. Gastellu, L. Jiang, A. Kuusk, P. Lewis, X. Li, W. Ni-Meister, T. Nilson, P. North, W. Qin, S. Tang, R. Thompson, W. Verhoef, H. Wang, J. Wang, G. Yan, H. Zang, 2004, "Radiation Transfer Model Intercomparison (RAMI) exercise: Results from the second phase", Journal of Geophysical Research 109, D06210, doi:10.1029/2003JD004252.

Reports

N.J.J. Bunnik and W. Verhoef, 1974, "The spectral directional reflectance of agricultural crops. Measurements on a wheat and a grass canopy for some stages of growth", NIWARS publ. no. 23.

W. Verhoef and N.J.J. Bunnik, 1975, "A model study on the relations between crop characteristics and canopy spectral reflectance. 1. Deduction of crop parameters from canopy reflectance data ; 2. Detectibility of variations in crop parameters by multispectral scanning", NIWARS publ. no. 33.

W. Verhoef and N.J.J. Bunnik, 1976, "The spectral directional reflectance of crops. 1. Consequences of non-Lambertian behaviour for automatic classification ; 2. Measurements on wheat and simulations by means of a reflectance model for row crops", NIWARS publ. no. 35.

W. Verhoef, 1983, "Simulation study of the radiometric aspects of the sun-object-sensor interaction for TERS in a true equatorial orbit", Memorandum RR-83-034 L.W.J. Looyen, W. Verhoef, J.G.P.W. Clevers, J. Lamers, J. Boerma, 1990, "Measurements of directional reflectance and acquisition of stereo information by CAESAR", NLR TP 90093 L.W. Verhoef, 1990, "Informatie-extractie uit multispectrale beelden met behulp van stralingsinteractiemodellen", NLR TP 90243 L.

W. Verhoef, H.J.C. van Leeuwen and J.G.P.W. Clevers, 1996, "Remote sensing assisted sugar beet yield forecasting", BCRS Report 95-24.

W. Verhoef, 1996, "Four-stream atmospheric correction model", NLR TP 96082 L.W. Verhoef and M. van Persie, 1996, "Influence of the observation conditions through the atmosphere for the visible sensor - EUCLID RTP 9.1/96/NLR/37210/FR", NLR CR 96387 L.

W. Verhoef and M. Menenti (eds.), 1998, "Final Report on Spatial and Spectral Scales for Spaceborne Imaging Spectro-radiometers (SASSSIS)", NLR CR-98213.

Conference papers

W. Verhoef and N.J.J. Bunnik, 1981, "Influence of crop geometry on multispectral reflectance determined by the use of canopy reflectance models", NLR MP 81042 U / Proc. International Coll. on spectral signatures of objects in remote sensing, Avignon (Fr), Sept. 1981.

N.J.J. Bunnik, W. Verhoef, R.W. de Jongh (NLR) and H.W.J. van Kasteren, R.H.M.E. Geerts, D. Uenk, H. Noordman, Th.A. de Boer (CABO), 1984,

"Evaluation of ground-based hot-spot reflectance measurements for biomass determination of agricultural crops", NLR MP 84085 U / Proc. "18th International Symposium on Remote Sensing of Environment", Paris, 1-5 Oct. 1984.

W. Verhoef, 1985, "A scene radiation model based on four-stream radiative transfer theory", NLR MP 85085 L / Proc. "3rd International Colloquium on spectral signatures of objects in remote sensing", Les Arcs (Fr), Dec. 1985.

W. Verhoef, 1988, "Numerical accuracy of a two-stream radiative transfer model from comparison with an N-stream model", NLR MP 88008 U / Proc. "4th International Colloquium on spectral signatures of objects in remote sensing", Aussois (Fr), Jan. 1988.

J.G.P.W. Clevers, H.J.C. van Leeuwen and W. Verhoef, 1992, "Estimating APAR by means of vegetation indices: a sensitivity analysis", Proc. XVIIth ISPRS Congress, Washington D.C., Aug. 2-14, 1992.

W. Verhoef, 2000, "Simultaneous retrieval of surface parameters by model inversion", ISPRS 2000 Congress, Amsterdam, July 2000.

W. Verhoef, 2000, "Spectral PPCA transform and spatial wavelets using lifting techniques for data compression of digital hyperspectral images", Proc. EOS/SPIE Symp. on Rem. Sens., Barcelona, Spain, Sept. 2000.

H. Bach, W. Verhoef and K. Schneider, 2000, "Coupling remote sensing observation models and a growth model for improved retrieval of (geo)biophysical information from optical remote sensing data", Remote Sensing for Agriculture, Ecosystems and Hydrology, SPIE Vol. 4171, pp. 1-11.

H. Bach, K. Schneider, W. Verhoef, R. Stolz, W. Mauser, H. van Leeuwen, L. Schouten, M. Borgeaud, 2001, "Retrieval of geo- and biophysical information from remote sensing through advanced combination of a land surface process model with inversion techniques in the optical and microwave spectral range", Proceedings of the 8th International Symposium "Physical measurements and signature in remote sensing", Aussois, CNES, pp.639-647.

W. Verhoef, 2002, "Improved modelling of multiple scattering in leaf canopies: the model SAIL++", Proc. 1st Int. Symp. on Recent Advances in Quantitative Remote Sensing (ed. J.A. Sobrino), Torrent, Spain, Sept. 2002, pp. 11-20.

Ph. D. thesisW. Verhoef, 1998, "Theory of radiative transfer models applied in optical remote sensing of vegetation canopies", Wageningen Agricultural University, The Netherlands, 310 pp.