Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Licht op licht: licht en verlichting in de pluimveehouderij in relatie tot beschadigend pikgedrag
    Niekerk, T.G.C.M. van; Ellen, H.H. ; Winkel, A. - \ 2015
    Livestock Research Wageningen UR (Livestock Research rapport 922) - 33
    pluimvee - licht - lichtregiem - gezichtsvermogen - verenpikken - pluimveehouderij - dierenwelzijn - dierlijke productie - hennen - huisvesting, dieren - diergezondheid - diergedrag - poultry - light - light regime - vision - feather pecking - poultry farming - animal welfare - animal production - hens - animal housing - animal health - animal behaviour
    In this report an overview is given of the technical knowledge with regards to light. light sources and the vision of poultry. Recent developments in lighting of poultry houses are mainly focused on new light sources, specifically LED, and the presence of daylight. Daylight comprises UV, which for poultry is a visual part of the spectrum. Chickens also see better in the red and green-blue spectrum. Technically it is possible to make lamps in the desired spectrum, but there is insufficient knowledge of the demands of the bird to be able to tune the lamps to their needs.
    Effects of nocturnal illumination on life-history decisions and fitness in two wild songbird species
    Jong, M.J. de; Ouyang, J. ; Silva, A. Da; Grunsven, R.H.A. van; Kempenaers, B. ; Visser, M.E. ; Spoelstra, K. - \ 2015
    Philosophical Transactions of the Royal Society B. Biological sciences 370 (2015). - ISSN 0962-8436 - 8 p.
    chemical magnetoreception - photoperiodic control - birds - light - mechanism - success - vision - dawn - date
    The effects of artificial night lighting on animal behaviour and fitness are largely unknown. Most studies report short-term consequences in locations that are also exposed to other anthropogenic disturbance. We know little about how the effects of nocturnal illumination vary with different light colour compositions. This is increasingly relevant as the use of LED lights becomes more common, and LED light colour composition can be easily adjusted. We experimentally illuminated previously dark natural habitat with white, green and red light, and measured the effects on life-history decisions and fitness in two free-living songbird species, the great tit (Parus major) and pied flycatcher (Ficedula hypoleuca) in two consecutive years. In 2013, but not in 2014, we found an effect of light treatment on lay date, and of the interaction of treatment and distance to the nearest lamp post on chick mass in great tits but not in pied flycatchers. We did not find an effect in either species of light treatment on breeding densities, clutch size, probability of brood failure, number of fledglings and adult survival. The finding that light colour may have differential effects opens up the possibility to mitigate negative ecological effects of nocturnal illumination by using different light spectra.
    Experimental illumination of natural habitat - an experimental set-up to assess the direct and indirect ecological consequences of artificial light of different spectral composition
    Spoelstra, K. ; Grunsven, R.H.A. van; Donners, M. ; Huijgens, T. ; Slaterus, R. ; Berendse, F. ; Visser, M.E. ; Veenendaal, E.M. - \ 2015
    Philosophical Transactions of the Royal Society B. Biological sciences 370 (2015). - ISSN 0962-8436 - 8 p.
    predation risk - beach mice - bats - night - ultraviolet - wavelength - pollution - responses - vision - time
    Artificial night-time illumination of natural habitats has increased dramatically over the past few decades. Generally, studies that assess the impact of artificial light on various species in the wild make use of existing illumination and are therefore correlative. Moreover, studies mostly focus on short-term consequences at the individual level, rather than long-term consequences at the population and community level—thereby ignoring possible unknown cascading effects in ecosystems. The recent change to LED lighting has opened up the exciting possibility to use light with a custom spectral composition, thereby potentially reducing the negative impact of artificial light. We describe here a large-scale, ecosystem-wide study where we experimentally illuminate forest-edge habitat with different spectral composition, replicated eight times. Monitoring of species is being performed according to rigid protocols, in part using a citizen-science-based approach, and automated where possible. Simultaneously, we specifically look at alterations in behaviour, such as changes in activity, and daily and seasonal timing. In our set-up, we have so far observed that experimental lights facilitate foraging activity of pipistrelle bats, suppress activity of wood mice and have effects on birds at the community level, which vary with spectral composition. Thus far, we have not observed effects on moth populations, but these and many other effects may surface only after a longer period of time.
    Stem localization of sweet-pepper plants using the support wire as a visual cue
    Bac, C.W. ; Hemming, J. ; Henten, E. van - \ 2014
    Computers and Electronics in Agriculture 105 (2014). - ISSN 0168-1699 - p. 111 - 120.
    autonomous robot - stereo - system - greenhouses - vision - images - rgb
    A robot arm should avoid collisions with the plant stem when it approaches a candidate sweet-pepper for harvesting. This study therefore aims at stem localization, a topic so far only studied under controlled lighting conditions. Objectives were to develop an algorithm capable of stem localization, using detection of the support wire that is twisted around the stem; to quantitatively evaluate performance of wire detection and stem localization under varying lighting conditions; to determine depth accuracy of stereo-vision under lab and greenhouse conditions. A single colour camera was mounted on a pneumatic slide to record image pairs with a small baseline of 1 cm. Artificial lighting was developed to mitigate disturbances caused by natural lighting conditions. An algorithm consisting of five steps was developed and includes novel components such as adaptive thresholding, use of support wires as a visual cue, use of object-based and 3D features and use of minimum expected stem distance. Wire detection rates (true-positive/scaled false-positive) were more favourable under moderate irradiance (94/5%) than under strong irradiance (74/26%). Error of stem localization was measured, in the horizontal plane, by Euclidean distance. Error was smaller for interpolated segments (0.8 cm), where a support wire was detected, than for extrapolated segments (1.5 cm), where a support wire was not detected. Error increased under strong irradiance. Accuracy of the stereo-vision system (±0.4 cm) met the requirements (±1 cm) in the lab, but not in the greenhouse (±4.5 cm) due to plant movement during recording. The algorithm is probably capable to construct a useful collision map for robotic harvesting, if the issue of inaccurate stereo-vision can be resolved by directions proposed for future work. This is the first study regarding stem localization under varying lighting conditions, and can be useful for future applications in crops that grow along a support wire.
    Image-based particle filtering for navigation in a semi-structured agricultural environment.
    Hiremath, S. ; Evert, F.K. van; Braak, C.J.F. ter; Stein, A. ; Heijden, G.W.A.M. van der - \ 2014
    Biosystems Engineering 121 (2014). - ISSN 1537-5110 - p. 85 - 95.
    automatic guidance - weed-control - robot - vision - segmentation - localization - vehicles - system - detect
    Autonomous navigation of field robots in an agricultural environment is a difficult task due to the inherent uncertainty in the environment. The drawback of existing systems is the lack of robustness to these uncertainties. In this study we propose a vision-based navigation method to address these problems. The focus is on navigation through a maize field in an outdoor environment where the robot has to navigate through a corridor formed by two plant rows, detect the end of the rows, navigate the headland and turn into another corridor under natural conditions. The method is based on a Particle Filter (PF) using a novel measurement model, where we construct a model image from the particle and compare it directly with the measurement image after elementary processing, such as down-sampling, excessive-green filtering and thresholding. The new measurement model does not extract features from the image and thus does not suffer from errors associated with the feature extraction process. We show how PF can be used for robust navigation of a robot in a semi-structured agricultural environment such as maize fields with inherent uncertainty. We demonstrate the robustness of the algorithm through experiments in several maize fields with different row patterns, varying plant sizes and diverse lighting conditions. To date we have logged over 5 km of successful test runs in which the robot navigates through the corridor without touching the plant stems, accurately detects the end of the rows and traverses the headland. (C) 2014 IAgrE. Published by Elsevier Ltd. All rights reserved.
    Automatic fruit recognition and counting from multiple images
    Song, Y. ; Glasbey, C.A. ; Horgan, G.W. ; Polder, G. ; Dieleman, J.A. ; Heijden, G.W.A.M. van der - \ 2014
    Biosystems Engineering 118 (2014). - ISSN 1537-5110 - p. 203 - 215.
    harvesting robot - orchard - vision - pepper - apples - number
    In our post-genomic world, where we are deluged with genetic information, the bottleneck to scientific progress is often phenotyping, i.e. measuring the observable characteristics of living organisms, such as counting the number of fruits on a plant. Image analysis is one route to automation. In this paper we present a method for recognising and counting fruits from images in cluttered greenhouses. The plants are 3-m high peppers with fruits of complex shapes and varying colours similar to the plant canopy. Our calibration and validation datasets each consist of over 28,000 colour images of over 1000 experimental plants. We describe a new two-step method to locate and count pepper fruits: the first step is to find fruits in a single image using a bag-of-words model, and the second is to aggregate estimates from multiple images using a novel statistical approach to cluster repeated, incomplete observations. We demonstrate that image analysis can potentially yield a good correlation with manual measurement (94.6%) and our proposed method achieves a correlation of 74.2% without any linear adjustment for a large dataset.
    Segmentation of Rumex obtusifolius using Gaussian Markov random fields
    Atni Hiremath, S. ; Tolpekin, V.A. ; Heijden, G. van der; Stein, A. - \ 2013
    Machine Vision Applications 24 (2013)4. - ISSN 0932-8092 - p. 845 - 854.
    energy minimization - texture features - weed-control - graph cuts - classification - systems - imagery - vision
    Rumex obtusifolius is a common weed that is difficult to control. The most common way to control weeds-using herbicides-is being reconsidered because of its adverse environmental impact. Robotic systems are regarded as a viable non-chemical alternative for treating R. obtusifolius and also other weeds. Among the existing systems for weed control, only a few are applicable in real-time and operate in a controlled environment. In this study, we develop a new algorithm for segmentation of R. obtusifolius using texture features based on Markov random fields that works in real-time under natural lighting conditions. We show its performance by comparing it with an existing real-time algorithm that uses spectral power as texture feature. We show that the new algorithm is not only accurate with detection rate of 97.8 % and average error of 56 mm in estimating the location of the tap-root of the plant, but is also fast taking just 0.18 s to process an image of size pixels making it feasible for real-time applications.
    Redefining environmental sustainability : Editorial overview
    Leemans, R. ; Solecki, W. - \ 2013
    Current Opinion in Environmental Sustainability 5 (2013)3-4. - ISSN 1877-3435 - p. 272 - 277.
    earth system science - challenges - planet - biodiversity - vision - impact
    Comparison of segmentation algorithms for cow contour extraction from natural barn background in side view images
    Hertem, T. van; Alchanatis, V. ; Antler, A. ; Maltz, E. ; Halachmi, I. ; Schlageter Tello, A.A. ; Lokhorst, C. ; Viazzi, S. ; Romanini, C.E.B. ; Pluk, A. ; Bahr, C. ; Berckmans, D. - \ 2013
    Computers and Electronics in Agriculture 91 (2013). - ISSN 0168-1699 - p. 65 - 74.
    dairy-cattle - automatic detection - digital images - body shape - lameness - locomotion - vision - behavior
    Computer vision techniques are a means to extract individual animal information such as weight, activity and calving time in intensive farming. Automatic detection requires adequate image pre-processing such as segmentation to precisely distinguish the animal from its background. For some analyses such as gait analysis, a side view perspective is recommended. When using a side view angle however, the background is more difficult to control – moving objects, such as other animals may negatively impact successful image segmentation. The objective of this research was to evaluate five different background segmentation algorithms on side view images when taken against a static background (a solid transportable wall) and a dynamic background (open air, without a wall). The experiments were conducted on a commercial robotic-milking dairy farm in Israel with a herd size of 70 Israeli Holstein cows. A side view image of cow’s gait was recorded after milking when the cows exited the milking area and returned to the cowshed. From the recording database, a random selection was made of 35 frames containing a static background (solid wall) and 20 frames containing a dynamic background (natural barn environment with other cows). Five segmentation algorithms were chosen and adapted from literature to extract the cow shape from the image. The output of three algorithms gave the cow’s full body shape two identified only the contour of the cow’s body. The algorithms were compared on their ability to correctly identify the cow’s back contour line. The performance of each algorithm was quantified by comparing its outputs to a golden standard of manually labelled cow pixels in the image. The introduction of a physical wall behind the cows (static background) significantly improved the foreground segmentation results (Mean Absolute Error (MAE) = 6.7 ± 5.7 pixels vs. 19.7 ± 9.1 pixels). The fourth algorithm, based on an edge detection on the background difference frame, gave the best cow back contour line segmentation results (b0 = -0.4 ± 15.5 and b1 = 1.00 ± 0.07). The fifth algorithm which is based on consecutive frame differences was less accurate than the other four methods which are based on the background frame differences (MAE = 16.0 ± 5.9 pixels vs. 4.1 ± 2.2 pixels, 4.3 ± 2.2 pixels, 5.6 ± 2.8 pixels and 3.7 ± 1.4 pixels respectively for the other four algorithms). The results show that the applied algorithms were not robust enough to work on side view images with dynamic backgrounds.
    Effects of Visual Priming on Taste-Odor Interaction
    Beilen, M. van; Bult, J.H.F. ; Renken, R. ; Stieger, M.A. ; Thumfart, S. ; Cornelissen, F. ; Kooijman, V.M. - \ 2011
    PLoS ONE 6 (2011)9. - ISSN 1932-6203 - 9 p.
    olfactory perception - sucrose solutions - perceived flavor - color - sweetness - discrimination - intensity - mixtures - texture - vision
    Little is known about the influence of visual characteristics other than colour on flavor perception, and the complex interactions between more than two sensory modalities. This study focused on the effects of recognizability of visual (texture) information on flavor perception of odorized sweet beverages. Participants rated the perceived sweetness of odorized sucrose solutions in the presence or absence of either a congruent or incongruent visual context. Odors were qualitatively reminiscent of sweet foods (strawberry and caramel) or not (savoury). Visual context was either an image of the same sweet foods (figurative context) or a visual texture derived from this product (non-figurative context). Textures were created using a texture synthesis method that preserved perceived food qualities while removing object information. Odor-taste combinations were rated sweeter within a figurative than a non-figurative context. This behaviour was exhibited for all odor-taste combinations, even in trials without images, indicating sustained priming by figurative visual context. A non-figurative context showed a transient sweetening effect. Sweetness was generally enhanced most by the strawberry odor. We conclude that the degree of recognizability of visual information (figurative versus non-figurative), influences flavor perception differently. Our results suggest that this visual context priming is mediated by separate sustained and transient processes that are differently evoked by figurative and non-figurative visual contexts. These components operate independent of the congruency of the image-odor-taste combinations.
    Autonomous navigation using a robot platform in a sugar beet field
    Bakker, T. ; Asselt, C.J. van; Bontsema, J. ; Müller, J. ; Straten, G. van - \ 2011
    Biosystems Engineering 109 (2011)4. - ISSN 1537-5110 - p. 357 - 368.
    mechanical weed-control - vehicles - vision - system - crops
    An RTK-DGPS (Real Time Kinematic Differential Global Positioning System) based autonomous field navigation system including automated headland turns was developed to provide a method for crop row mapping combining machine vision, and to evaluate the benefits of a behaviour based reactive layer in a hybrid deliberate systems architecture. Two experiments were performed at the same time: following of pre-planned paths reconstructed from crop row positions based on RTK-DGPS and crop row mapping by combining vision-based row detection with RTK-DGPS information. The standard deviation, mean, minimum and maximum lateral error of the robot vehicle while following a straight path on the field with RTK-DGPS at a speed of 0.3 m s-1 were respectively 1.6, 0.1, -4.5 and 3.4 cm. The standard deviation, mean, minimum and maximum of the heading error were 0.008, 0.000, -0.022 and 0.023 rad. The point-in-polygon algorithm proved to be a suitable method for detection in which part of the field the actuator position coordinates or the field of view of the camera are located. A smooth headland path that connected to the subsequent path along the crop was generated in realtime using a spline based algorithm. The hybrid deliberate software architecture with a behaviour based reactive layer allowed a convenient evaluation of the robot performance. Results from the field experiments showed that the implement can be guided along a defined path with cm precision using an autonomous robot navigating in a field.
    Bounded transparency for automated inspection in agriculture
    Koenderink, N.J.J.P. ; Broekstra, J. ; Top, J.L. - \ 2010
    Computers and Electronics in Agriculture 72 (2010)1. - ISSN 0168-1699 - p. 27 - 36.
    knowledge - vision - systems
    In agriculture, a major challenge is to automate knowledge-intensive tasks. Task-performing software is often opaque, which has a negative impact on a system’s adaptability and on the end user’s understanding and trust of the system’s operation. A more transparent, declarative way of specifying the expert knowledge required in such software is needed. We argue that a white-box approach is in principle preferred over systems in which the applied expertise is hidden in the system code. Internal transparency makes it easier to adapt the system to new conditions and to diagnose faulty behaviour. At the same time, explicitness comes at a price and is always bounded by practical considerations. Therefore we introduce the notion of bounded transparency, implying a balanced decision between transparency and opaqueness. The method proposed in this paper provides a set of pragmatic objectives and decision criteria to decide on each level of a task’s decomposition whether more transparency is sensible or whether delegation to a black-box component is acceptable. We apply the proposed method in a real-world case study involving a computer vision application for seedling inspection in horticulture and show how bounded transparency is obtained. We conclude that the proposed method offers structure to the application designer in making substantiated implementation decisions
    Systematic design of an autonomous platform for robotic weeding
    Bakker, T. ; Asselt, C.J. van; Bontsema, J. ; Müller, J. ; Straten, G. van - \ 2010
    Journal of Terramechanics 47 (2010)2. - ISSN 0022-4898 - p. 63 - 73.
    sugar-beet - obstacle detection - vision - guidance - crops - technology - laser - time
    The systematic design of an autonomous platform for robotic weeding research in arable farming is described. The long term objective of the project is the replacement of hand weeding in organic farming by a device working autonomously at field level. The distinguishing feature of the described design procedure is the use of a structured design approach, which forces the designer to systematically review and compare alternative solution options, thus preventing the selection of solutions based on prejudice or belief. The result of the design is a versatile research vehicle with a diesel engine, hydraulic transmission, four-wheel drive and four-wheel steering. The robustness of the vehicle and the open software architecture permit the investigation of a wide spectrum of research options for intra-row weed detection and weeding actuators
    Gezichtsvermogen varken ook bij veel licht beperkt
    Zonderland, J.J. ; Cornelissen, J.B.W.J. - \ 2007
    V-focus 2007 (2007)4. - ISSN 1574-1575 - p. 48 - 49.
    varkenshouderij - varkens - gezichtsvermogen - lichtsterkte - verlichting - pig farming - pigs - vision - light intensity - lighting
    In opdracht van het Productschap Vee en Vlees heeft ASG het vermogen van varkens om visuele signalen te onderscheiden onderzocht bij verschillende lichtintensiteiten
    Duikers in de mist : wetenschappelijk onderzoek naar de mate van doorzicht rondom onderwaterhuis 'Aquavilla' in een diepe duikplas
    Hal, M. van; Lürling, M.F.L.L.W. - \ 2004
    Wageningen : Wageningen UR, Wetenschapswinkel (Rapport / Wetenschapswinkel Wageningen UR 195) - ISBN 9789067547550 - 110
    duiken - waterkwaliteit - zichtbaarheid - gezichtsvermogen - plassen - land van maas en waal - diving - water quality - visibility - vision - ponds - land van maas en waal
    Veiligheid staat bij Duikteam De Kaaiman hoog in het vaandel. Duiken in troebel water kan gevaarlijk zijn en is dus ongewenst. Ook verhoogt helder water het duikgenot. In het meer de Berendonck bij Wijchen, de vaste duikstek van De Kaaiman, ligt op een diepte van 17 meter een onderwaterhuis. Vooral rondom dit huis is sprake van slecht zicht. Waardoor komt dit en wat is er aan te doen?
    Accurate measurement of size and shape of cucumber fruits with image analysis
    Eck, J.W. van; Heijden, G.W.A.M. van der; Vossepoel, A.M. ; Polder, G. - \ 1998
    Journal of Agricultural Engineering Research 70 (1998)4. - ISSN 0021-8634 - p. 335 - 343.
    vision
    An accurate method was developed, using image analysis, for measurement of the length width and shape of cucumber fruits. Determination of the local width along the mid-line of the fruit, enabled a condensed description of the fruit to be given. From this condensed description, size and shape features can be extracted, such as length, width and neck-shape of cucumber fruits. Tests showed that the image analysis method was effective and efficient for determining shape features which are visually difficult to score. Comparison with the manually obtained results showed that the measurement errors for image analysis were much lower than the ones made by the observer, e.g. the standard deviation of cucumber length was 1·4 mm with image analysis and 3·5 mm by manual measurement. The proposed method has more general applicability and may be of interest for studying the shape of other elongated symmetrical objects
    Functies van vitamine A in het lichaam.
    West, C.E. - \ 1989
    Voeding 50 (1989)6/7. - ISSN 0042-7926 - p. 146 - 151.
    perceptie - retinol - gezichtsvermogen - vitaminen - perception - retinol - vision - vitamins
    Historische achtergrond van vitamine A en nachtblindheid als belangrijkste deficientieziekte
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