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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Cruiserapport scheepstellingen van zeevogels op het Friese Front en op de Bruine Bank, 2016
Geelhoed, S.C.V. ; Leopold, M.F. - \ 2017
Den Helder : Wageningen Marine Research (IMARES rapport C032/17) - 36
zeevogels - noordzee - monitoring - luchtkarteringen - zeezoogdieren - biodiversiteitsbepaling - natura 2000 - sea birds - north sea - aerial surveys - marine mammals - biodiversity assessment
Het Friese Front en de Bruine Bank zijn twee nieuwe Vogelrichtlijngebieden in de Noordzee. Het Friese Front is aangewezen voor de Zeekoet. De Bruine Bank wordt waarschijnlijk aangewezen voor Zeekoet en Alk. Om te bepalen of de instandhoudingsdoelstellingen voor deze soorten worden gehaald, moeten de aantallen van deze soorten gemonitord worden. Monitoring van zeevogels in het Nederlandse deel van de Noordzee vindt plaats met behulp van MWTL-vliegtuigtellingen. Alken en Zeekoeten kunnen vanuit de lucht echter lastig van elkaar te onderscheiden zijn. Vanaf schepen is de herkenning eenvoudiger. Het onderhavige BO-project 'scheepstellingen zeevogels' dat in 2016-2018 loopt, heeft tot doel inzicht te geven in de aantallen van Alken en Zeekoeten in beide gebieden enerzijds, en anderzijds in de veranderingen in aantalsverhouding tussen beide soorten gedurende het jaar om de MWTL-vliegtuigtellingen te calibreren. In 2016 zijn drie scheerpssurveys uitgevoerd op het Friese Front (30 okt-4 nov) en op de Bruine Bank (14-17 mrt, 27 nov-1 dec). Op de Bruine Bank werden in maart 6021 individuen van 32 verschillende vogelsoorten geteld. Kleine Mantelmeeuw (n =1287), Drieteenmeeuw (n = 1101), Zeekoet (n = 1087) en Alk (n = 1081) domineerden de telling. Daarnaast werden 17 individuen verdeeld over drie soorten zeezoogdieren (Bruinvis, Gewone en Grijze Zeehond) geregistreerd. Tijdens de survey op het Friese Front in november werden 4184 individuen verdeeld over 36 verschillende vogelsoorten geteld. Zeekoet (n = 1364) en Alk (n = 628) waren de dominante soorten. Daarnaast werden 103 individuen verdeeld over drie soorten zeezoogdieren gezien. In november werden op de Bruine Bank 4356 individuen verdeeld over 24 verschillende vogelsoorten geteld. Zeekoet (n = 1326), Grote Mantelmeeuw (n = 1091) en Drieteenmeeuw (n = 878) domineerden de survey. Het aantal Alken (n = 162) was relatief laag. Daarnaast werden 50 Bruinvissen geregistreerd. Tijdens alle surveys behoorden Alken en Zeekoeten tot de talrijkste soorten. De verhouding tussen Alk en Zeekoet varieerde van 1:1 in maart op de Bruine Bank tot 1:8 op de Bruine Bank in november. Behalve van alkachtigen werden ook gegevens verzameld van potentieel kwalificerende N2000-soorten Kleine Mantelmeeuw (mrt Bruine Bank), Grote Mantelmeeuw (nov Friese Front en Bruine Bank) en Grote Jager (nov Friese Front en Bruine Bank). Dit rapport geeft een beknopt overzicht van de resultaten van de surveys in 2016. In 2018 worden de resultaten van deze en aanvullende surveys nader uitgewerkt en gepresenteerd in een eindrapportage.
Gemini T-0: passive acoustic monitoring and aerial surveys of harbour porpoises
Geelhoed, S.C.V. ; Friedrich, E. ; Joost, M. ; Juhre, H. ; Kirkwood, R.J. ; Leeuwen, P.W. van; Machiels, M.A.M. ; Stoeber, N. ; Verdaat, J.P. - \ 2015
Den Burg : IMARES (Report / IMARES Wageningen UR C144/15) - 110
phocoenidae - akoestisch sporen - luchtkarteringen - monitoring - offshore - windmolenpark - noordzee - nederland - acoustic tracking - aerial surveys - wind farms - north sea - netherlands
In accordance with the monitoring and evaluation plan (MEP) for the ‘Gemini Offshore Wind Farm’ the ecological monitoring of harbour porpoises was carried out by IMARES and IBL Umweltplanung, concerning the distribution and numbers of harbour porpoises in and around the wind farm prior to construction (T-0). For this purpose aerial surveys as well as passive acoustic monitoring were performed.
Marine mammal surveys in Dutch waters in 2014
Geelhoed, S.C.V. ; Lagerveld, S. ; Verdaat, J.P. ; Scheidat, M. - \ 2014
Den Burg : IMARES (Report / IMARES Wageningen UR C180/14) - 19
zeezoogdieren - luchtkarteringen - monitoring - noordzee - marine mammals - aerial surveys - north sea
In July 2014 aerial surveys to estimate the abundance of Harbour porpoises Phocoena phocoena on the Dutch Continental Shelf were conducted. In total, 229 sightings of 273 individual Harbour Porpoises were collected. Porpoise densities varied between 0.37-3.08 animals/km² in the (four) different areas. The overall density on the entire Dutch Continental Shelf was 1.29 animals/km².
Marine mammal surveys in Dutch waters in 2013
Geelhoed, S.C.V. ; Scheidat, M. ; Bemmelen, R.S.A. van - \ 2014
Den Burg : IMARES (Report / IMARES Wageningen UR C027/14) - 22
luchtkarteringen - zeezoogdieren - monitoring - noordzee - aerial surveys - marine mammals - north sea
In March/April 2013 aerial surveys to estimate the abundance of Harbour porpoises Phocoena phocoena on the Dutch Continental Shelf were conducted. These surveys were conducted along predetermined track lines using distance sampling methods in four areas: A “Dogger Bank”, B “Offshore”, C “Frisian Front” & D “Delta”. Between 18 March and 22 April the entire Dutch Continental Shelf (DCS) was surveyed. In total, 197 sightings of 223 individual Harbour Porpoises were collected. Porpoise densities varied between 0.47-1.44 animals/km² in the areas A-D. The overall density on the entire Dutch Continental Shelf was 1.07 animals/km². Harbour Porpoises were widely distributed in March with higher densities in area D “Delta”. In the northern part of the DSC the distribution seemed more patchy, with lower densities in the northern part of area B “Offshore” and in area A “Dogger Bank”.
Marine mammal surveys in the wider Dogger Bank area summer 2013
Geelhoed, S.C.V. ; Bemmelen, R.S.A. van; Verdaat, J.P. - \ 2014
Den Burg : IMARES (Report / IMARES Wageningen UR C016/14) - 27
zeezoogdieren - luchtkarteringen - monitoring - noordzee - marine mammals - aerial surveys - north sea
In summer 2013 aerial surveys using distance sampling methods where conducted in UK, Dutch, German and Danish waters to investigate the occurrence of marine mammals in the Dogger Bank area. The Dogger Bank is a candidate Special Area of Conservation (cSAC) under the EC Habitats Directive (Natura 2000) and part of the OSPAR network of Marine Protected Areas in the North East Atlantic Ocean.
Aerial surveys of marine mammals and other fauna around Aruba, Curacao and Bonaire, November 2013
Geelhoed, S.C.V. ; Janinhoff, N. ; Verdaat, J.P. ; Bemmelen, R.S.A. van; Scheidat, M. - \ 2014
Den Burg : IMARES (Report / IMARES Wageningen UR C012/14) - 22
luchtkarteringen - fauna - zoogdieren - inventarisaties - mariene gebieden - caribisch gebied - aerial surveys - mammals - inventories - marine areas - caribbean
In November 2013 aerial surveys were conducted for the first time in the Exclusive Economic Zone of Aruba, Curaçao and Bonaire to evaluate aerial surveys as a tool for marine mammal surveys in these waters, and to assess the distribution and abundance of marine mammals. A secondary aim of these surveys was to collect data on the occurrence of other megafauna (e.g. sharks, rays, turtles) and seabirds. Marine mammals were assessed using distance sampling methods; for other species a strip transect method was applied.
Effects of pile-driving on harbour porpoises (Phocoena phocoena) at the first offshore wind farm in Germany
Daehne, M. ; Gilles, A. ; Lucke, K. ; Peschko, V. ; Adler, S. ; Kruegel, K. ; Sundermeyer, J. ; Siebert, U. - \ 2013
Environmental Research Letters 8 (2013)2. - ISSN 1748-9326
air bubble curtain - north-sea - underwater noise - aerial surveys - baltic sea - detection thresholds - marine mammals - t-pods - waters - abundance
The first offshore wind farm 'alpha ventus' in the German North Sea was constructed north east of Borkum Reef Ground approximately 45 km north off the German coast in 2008 and 2009 using percussive piling for the foundations of 12 wind turbines. Visual monitoring of harbour porpoises was conducted prior to as well as during construction and operation by means of 15 aerial line transect distance sampling surveys, from 2008 to 2010. Static acoustic monitoring (SAM) with echolocation click loggers at 12 positions was performed additionally from 2008 to 2011. SAM devices were deployed between 1 and 50 km from the centre of the wind farm. During aerial surveys, 18¿600 km of transect lines were covered in two survey areas (10¿934 and 11¿824 km2) and 1392 harbour porpoise sightings were recorded. Lowest densities were documented during the construction period in 2009. The spatial distribution pattern recorded on two aerial surveys three weeks before and exactly during pile-driving points towards a strong avoidance response within 20 km distance of the noise source. Generalized additive modelling of SAM data showed a negative impact of pile-driving on relative porpoise detection rates at eight positions at distances less than 10.8 km. Increased detection rates were found at two positions at 25 and 50 km distance suggesting that porpoises were displaced towards these positions. A pile-driving related behavioural reaction could thus be detected using SAM at a much larger distance than a pure avoidance radius would suggest. The first waiting time (interval between porpoise detections of at least 10 min), after piling started, increased with longer piling durations. A gradient in avoidance, a gradual fading of the avoidance reaction with increasing distance from the piling site, is hence most probably a product of an incomplete displacement during shorter piling events.
Met Okkie de lucht in : Wageningen gebruikt drone voor remote sensing
Kooistra, Lammert - \ 2012
remote sensing - geoinformation - aerial surveys - remote control - drones - applications - agriculture
Monitoring marine populations and communities: methods dealing with imperfect detectability
Katsanevakis, S. ; Weber, A. ; Pipitone, C. ; Leopold, M.F. ; Scheidat, M. ; Boois, I.J. de; Jansen, J.M. - \ 2012
Aquatic Biology 16 (2012)1. - ISSN 1864-7782 - p. 31 - 52.
estimating animal abundance - visual census techniques - capture-recapture data - line-transect surveys - change-in-ratio - reef fish - aerial surveys - harbor porpoise - phoca-vitulina - parameter-estimation
Effective monitoring of populations and communities is a prerequisite for ecosystem-based management of marine areas. However, monitoring programs often neglect important sources of error and thus can lead to biased estimates, spurious conclusions and false management actions. One such source of error is ‘imperfect detectability’, i.e. the inability of investigators to detect all individuals or all species in a surveyed area. Although there has been great effort to develop monitoring methods that account for imperfect detectability, the application of such methods in the marine environment is not as apparent as in other systems. Plot sampling is by far the most commonly applied method for biological monitoring in the marine environment, yet it largely ignores detectability issues. However, distance sampling, mark-recapture methods, repeated presence-absence surveys for occupancy estimation, and removal methods do estimate detection probabilities and provide unbiased estimates of state variables. We review these methods and the relevant tools for their application in studies on marine populations and communities, with the aim of assisting marine biologists and managers to understand the limitations and pitfalls associated with some approaches and to select the best available methods for their monitoring needs
Identifying transit corridors for elephant using a long time-series
Pittiglio, C. ; Skidmore, A.K. ; Gils, H.A.M.J. van; Prins, H.H.T. - \ 2012
International Journal of applied Earth Observation and Geoinformation 14 (2012)1. - ISSN 0303-2434 - p. 61 - 72.
species distribution models - manyara-national-park - northern tanzania - southern africa - aerial surveys - movement corridors - wildlife corridors - loxodonta-africana - simanjiro plains - plant phenology
The role of corridors in mitigating the effects of landscape fragmentation on biodiversity is controversial. Recent studies have highlighted the need for new approaches in corridor design using long-term datasets. We present a method to identify transit corridors for elephant at a population scale over a large area and an extended period of time using long-term aerial surveys. We investigated environmental and anthropogenic factors directly and indirectly related to the wet versus dry season distribution of elephant and its transit corridors. Four environmental variables predicted the presence of elephant at the landscape scale in both seasons: distance from permanent water, protected areas and settlements and vegetation structure. Path analysis revealed that altitude and monthly average NDVI, and distance from temporary water had a significant indirect effect on elephant distribution at local scale in dry and wet seasons respectively. Five transit corridors connecting Tarangire National Park and the northern as well as south-eastern wet season dispersal areas were identified and matched the wildlife migration routes described in the 1960s. The corridors are stable over the decades, providing landscape connectivity for elephant. Our approach yielded insights how advanced spatial analysis can be integrated with biological data available from long-term datasets to identify actual transit corridors and predictors of species distribution.
Aantallen en verspreiding van Eiders, Toppers en zee-eenden in de winter van 2010 - 2011
Smit, C.J. ; Jong, M.L. de - \ 2011
Den Burg : IMARES (Rapport / IMARES Wageningen UR C196/11) - 30
eenden - zoögeografie - monitoring - luchtkarteringen - waddenzee - ducks - zoogeography - aerial surveys - wadden sea
Dit rapport beschrijft de resultaten van de vliegtuigtellingen van november en december 2010 en februari 2011, die zijn uitgevoerd om de aantallen en verspreiding vast te stellen van overwinterende Eiders Somateria mollissima, Zwarte Zee-eenden Melanitta nigra, Grote Zee-eenden Melanitta fusca en Toppers Aythya marila in de Waddenzee en de aangrenzende Noordzeekustzone. In november 2010 werden 63.717 Eiders, 4209 Zwarte Zee-eenden en 10.960 Toppers geteld. In december 2010 waren de aantallen Eiders en Zwarte Zee-eenden lager en van de Toppers hoger: 53.662 Eiders, 1857 Zwarte Zee-eenden en 29.235 Toppers. In februari 2011 waren de aantallen Zwarte Zee-eenden vergelijkbaar met november 2010, maar waren de aantallen Eiders sterk afgenomen. In deze maand werden geen Toppers meer gezien maar wel 38.074 Eiders en 4167 Zwarte Zee-eenden. Tijdens alle drie tellingen zijn er geen Grote Zee-eenden waargenomen.
Seasonal distribution of harbour porpoises and possible intereference of offshore wind farms in the German North Sea
Gilles, A. ; Scheidat, M. ; Siebert, U. - \ 2009
Marine Ecology Progress Series 383 (2009). - ISSN 0171-8630 - p. 295 - 307.
phocoena-phocoena - aerial surveys - underwater noise - marine mammals - life-history - baltic sea - cetaceans - abundance - waters - bight
The seasonal distribution of harbour porpoises in the German North Sea was investigated, hot spot areas were identified and the proportion of porpoises potentially affected by the imminent construction of offshore wind farms was estimated. Data were collected during dedicated aerial surveys conducted year-round between 2002 and 2006 following line transect methodology. Survey effort amounted to 44 739 km during which a total of 5121 harbour porpoises was detected, including 258 calves. Our data suggest that porpoises move to distinct areas on a seasonal basis as their biological requirements change. They move into German waters in early spring, reach high numbers in early summer and move out of the area in autumn. The abundance estimates for the German exclusive economic zone and 12 n mile zone were highest in spring (55 048 animals; 95% CI: 32 395 to 10 1671) and summer (49 687 animals; 95% CI: 29 009 to 96 385) and lowest in autumn with 15 394 animals (95% CI: 8906 to 29 470). Important aggregation zones were detected in offshore waters: in spring, 2 hot spots, Borkum Reef Ground and Sylt Outer Reef (SOR), were identified as key foraging areas. In summer, only the large hot spot SOR persisted, causing a strong north¿south density gradient. In autumn, porpoises were more evenly distributed. Most mother-calf pairs were observed during spring and summer in the SOR, underlining its importance as a foraging area when reproductive costs are high. Spatial overlap exists between important areas for porpoises and areas where offshore wind farms are currently licensed or planned. The proportion of the national stock possibly exposed to the construction noise of 18 licensed wind farms was estimated applying different scenarios. Within a 20 km zone of responsiveness - as worst case scenario - 39% of the harbour porpoise stock in the German EEZ could be affected during construction.
Development of analysis techniques for the use of aerial photography in the monitoring of intertidal mussel beds and oyster beds
Fey-Hofstede, F.E. ; Cremer, J.S.M. ; Dijkman, E.M. ; Jansen, J.M. ; Roupioz, L.F.S. ; Schmidt, A.M. - \ 2009
Texel : IMARES (Report / Wageningen IMARES C004/09) - 27
mossels - luchtkarteringen - zoögeografie - kustgebieden - schaal- en schelpdierenvisserij - monitoring - mariene gebieden - wadden - visstand - mussels - aerial surveys - zoogeography - coastal areas - shellfish fisheries - marine areas - tidal flats - fish stocks
This project aimed at improving the analysis techniques of aerial photography for mussel bed recognition and mapping. In this project two techniques were tested; recognition and mapping by human eye and recognition and mapping by automatic detection software. The detection with the human eye was tested in two ways. The first test considered recognition of mussel beds in an area were contours of the previous year were available. The second test concerned a blind recognition test without any knowledge on previous locations of mussel beds.
Google Earth based visualization of Sustainable Outlook(GESO)
Lammeren, R.J.A. van; Hilferink, M. ; Bergsma, A.R. ; Beek, M. - \ 2008
Wageningen : CGI (CGI report 2008-03) - 43
landgebruik - luchtkarteringen - afbeelden - 3d visualisatie - land use - aerial surveys - imagery - 3d visualization
GESO is a tool to prepare a Google Earth visualisation of the Dutch land use scenarios as created by the Netherlands Environmental Assessment Agency. This Google Earth for the Sustainable Outlook application, named GESO, forms an update of the previous VisualScan attempt. The GESO application aims to be an effective, easy and low cost way to study Sustainable Outlook data via an interactive 3D visualization that integrates the land use icon and landscape feature approach as presented in the VisualScan study. The concept and implementation of GESO are explained and many examples of using GESO are given. The final chapter concludes and discusses the results and gives content-wise and technical recommendations for follow up projects.
Ecologische atlas Waddenzee
Dankers, N.M.J.A. ; Cremer, J.S.M. ; Dijkman, E.M. ; Brasseur, S.M.J.M. ; Dijkema, K.S. ; Fey-Hofstede, F.E. ; Jong, M.L. de; Smit, C.J. - \ 2007
Texel : IMARES
habitats - ecologie - geomorfologie - sediment - luchtkarteringen - kaarten - aquatische ecologie - waddenzee - ecology - geomorphology - aerial surveys - maps - aquatic ecology - wadden sea
Deze atlas is samengesteld met informatie uit verschillende bronnen, en bestaat uit gecombineerde kaarten van luchtfoto’s en geomorfologische informatie. Voor het beleid is het belangrijk dat uit de kaarten op te maken is waar kenmerkende landschapstypen liggen, en dan vooral die typen die in nationale of internationale regelgeving een bepaalde status hebben, zoals de habitattypen uit de EU-habitatrichtlijn, of kenmerken die essentieel zijn voor de kwaliteit van de EU-habitats. Binnen de EU-habitattypen zoals droogvallende wadplaten en kwelders is het mogelijk een verdere onderverdeling te geven op basis van sedimentsamenstelling, dynamiek en successiestadium in de vegetatieontwikkeling
AeroBanMan: the aerial detection of plant distribution and fungus infection for precision banana management
Stoorvogel, J.J. ; Verhoeven, R. ; Leeuwen, H. van; Orlich, R. - \ 2001
Wageningen : Lab of Soil Science and Geology WAU (NRSP-2 01-39) - ISBN 9789054113805 - 46
remote sensing - biogeografie - luchtkarteringen - ziektedistributie - plantenziekten - plantagegewassen - bananen - schimmelziekten - mycosen - precisielandbouw - biogeography - aerial surveys - disease distribution - plant diseases - plantation crops - bananas - fungal diseases - mycoses - precision agriculture
Geographical information modelling for land resource survey
Bruin, S. de - \ 2000
Agricultural University. Promotor(en): M. Molenaar; Arnold Bregt. - S.l. : S.n. - ISBN 9789058082114 - 131
bruikbaar land - landgebruik - luchtkarteringen - cartografie - geografische informatiesystemen - gegevensanalyse - gegevens verzamelen - beeldverwerking - modellen - spanje - digitaal terreinmodel - land resources - land use - aerial surveys - mapping - geographical information systems - data analysis - data collection - image processing - models - spain - digital elevation model

The increasing popularity of geographical information systems (GIS) has at least three major implications for land resources survey. Firstly, GIS allows alternative and richer representation of spatial phenomena than is possible with the traditional paper map. Secondly, digital technology has improved the accessibility of ancillary data, such as digital elevation models and remotely sensed imagery, and the possibilities of incorporating these into target database production. Thirdly, owing to the greater distance between data producers and consumers there is a greater need for uncertainty analysis. However, partly due to disciplinary gaps, the introduction of GIS has not resulted in a thorough adjustment of traditional survey methods. Against this background, the overall objective of this study was to explore and demonstrate the utility of new concepts and tools within the context of pedological and agronomical land surveys. To this end, research was conducted on the interface between five fields of study: geographic information theory, land resource survey, remote sensing, statistics and fuzzy set theory. A demonstration site was chosen around the village of Alora in southern Spain.

Fuzzy set theory provides a formalism to deal with classes that are partly indistinct as a result of vague class intensions. Fuzzy sets are characterised by membership functions that assign real numbers from the interval [0, 1] to elements, thereby indicating the grade of membership in that set. When fuzzy membership functions are used to classify attribute data linked to geometrical elements, presence of spatial dependence among these elements ensures that they form spatially contiguous regions. These can be interpreted as objects with indeterminate boundaries or fuzzy objects. Fuzzy set theory thus adds to the conventional conceptual data models that assume either discrete spatial objects or continuous fields.

This thesis includes two case studies that demonstrate the use of the fuzzy set theory in the acquisition and querying of geographical information. The first study explored the use of fuzzy c -means clustering of attribute data derived from a digital elevation model to represent transition zones in a soil-landscape model. Validity evaluation of the resulting terrain descriptions was based on the coefficient of determination of regressing topsoil clay data on membership grades. Vaguely bounded regions were more closely related to the observed variation of clay content () than crisply bounded units as used in a conventional soil survey ().

The second case study involved the use of the fuzzy set theory in querying uncertain geographical data. It explains differences between fuzziness and stochastic uncertainty on the basis of an example query concerning loss of forest and ease of access. Relationships between probabilities and fuzzy set memberships were established using a linguistic probability qualifier (high probability) and the expectation of a membership function defined on a stochastic travel time. Fuzzy query processing was compared with crisp processing. The fuzzy query response contained more information because, unlike the crisp response, it indicated the degree to which individual locations matched the vague selection criteria.

In a land resource survey, data acquisition typically involves collecting a small sample of precisely measured primary data as well as a larger or even exhaustive sample of related secondary data. Soil surveyors often rely on soil-landscape relationships and image interpretation to enable efficient mapping of soil properties. Yet, they generally fail to communicate about the knowledge and methods employed in deriving map units and statements about their content.

In this thesis, a methodological framework is formulated and demonstrated that takes advantage of GIS to interactively formalise soil-landscape knowledge using stepwise image interpretation and inductive learning of soil-landscape relationships. It examines topology to record potential part of links between hierarchically nested terrain objects corresponding to distinct soil formation regimes. These relationships can be applied in similar areas to facilitate image interpretation by restricting possible lower level objects. GIS visualisation tools can be used to create images (e.g. perspective views) illustrating the landscape configuration of interpreted terrain objects. The framework is expected to support different methods for analysing and describing soil variation in relation to a terrain description, including those requiring alternative conceptual data models. In this thesis, though, it is only demonstrated with the discrete object model.

Satellite remote sensing has become an important tool in land cover mapping, providing an attractive supplement to relatively inefficient ground surveys. A common approach to extract land cover data from remotely sensed imagery is by probabilistic classification of multispectral data. Additional information can be incorporated into such classification, for example by translating it into Bayesian prior probabilities for each land cover type. This is particularly advantageous in the case of spectral overlap among target classes, i.e. when unequivocal class assignment based on spectral data alone is impossible.

This thesis demonstrates a procedure to iteratively estimate regional prior class probabilities pertaining to areas resulting from image stratification. This method thus allows the incorporation of additional information into the classification process without the requirement of known prior class probabilities. The demonstration project involved Landsat TM imagery from 1984 and 1995. Image stratification was based on a geological map of the study area. Overall classification accuracy improved from 76% to 90% (1984) and from 64% to 69% (1995) when employing iteratively estimated prior probabilities.

The fact that any landscape description is a model based on a limited sample of measured target attribute data implies that it is never completely certain. The presence of error or inaccuracy in the data contributes significantly to such uncertainty. Usually, the accuracy of land survey datasets is indicated using global indices (e.g. see above). Error modelling, on the other hand, allows an indication of the spatial distribution of possible map inaccuracies to be given. This study explored two approaches to error modelling, which are demonstrated within the context of land cover analysis using remotely sensed imagery.

The first approach involves the use of local class probabilities conditional to the pixels' spectral data. These probabilities are intermediate results of probabilistic image classification and indicate the magnitude and distribution of classification uncertainty. A case study demonstrated the implication of such uncertainty on change detection by comparing independently classified images. A major shortcoming of this approach is that it implicitly assumes data in neighbouring pixels to be independent. Moreover, it does not make full use of available reference data as it ignores their spatial component. It does not consider data locations nor does it use spatial dependence models that can be derived from the reference data.

The assumption of independent pixels obviously impedes proper assessment of spatial uncertainty, such as joint uncertainty about the land cover class at several pixels taken together. Therefore, the second approach was based on geostatistical methods, which exploit spatial dependence rather than ignoring it. It is demonstrated how the above conditional probabilities can be updated by conditioning on sampled reference data at their locations. Stochastic simulation was used to generate a set of 500 equally probable maps, from which uncertainties regarding the spatial extent of contiguous olive orchards could be inferred.

Future challenges include studies on other quality aspects of land survey datasets. The present research was limited to uncertainty analysis, so that, for example, data precision and fitness for use were not addressed. Other potential extensions to this work concern full inclusion of the third spatial dimension and modelling of temporal aspects.

Remotely sensed hydrological isolation : a key factor predicting plant species distribution in fens
Sanders, M.E. - \ 1999
Agricultural University. Promotor(en): M. Molenaar; G.B.M. Pedroli. - S.l. : S.n. - ISBN 9789058080738 - 136
planten - soorten - distributie - wetlands - remote sensing - luchtkarteringen - vegetatietypen - bedrijfsvoering - kaarten - nationale parken - nederland - overijssel - natuur - plants - species - distribution - aerial surveys - vegetation types - management - maps - national parks - netherlands - nature
<p>In fens the species composition, vegetation structure and succession rate are determined by vegetation management and water chemistry, particularly by the base status and nutrient status. Base-rich and nutrient-rich surface water causes fens to become eutrophied, which leads to an increased biomass production. When part of fens becomes isolated from this surface water (hydrological isolation), it acidifies due to acidic and oligotrophic rainwater dominance. One consequence of decreasing water quality due to continuing acidification and eutrophication, is the disappearance of the rare plant species that depend on base-rich but oligotrophic water. It is important to obtain quantitative information on the influence of these processes on vegetation structure types and the distribution of rare plant species to support management planning and evaluation. The usual method to obtain this information is fieldwork, but this is time consuming and thus very expensive, especially in large, inaccessible areas like wetlands. The aim of this study was therefore to investigate the efficiency of remote sensing and geographical information systems (GIS) to identify hydrological isolation in order to predict the distribution of rare plant species.</p><H3>De Weerribben study area</H3><p>Dutch inland wetlands are characterized human impacts. The peat cutting and dredging in the 18th and 19th centuries formed a landscape of extensive rectangular bodies of open water (ca. 30 by 1000 m) called <em>petgaten</em> . After the <em>petgaten</em> were abandoned, a process of terrestrialization from open water to fen vegetation began, in which the first stage is the formation of a floating raft of vegetation. The reeds on the floating rafts were mown every year for thatch. When not mown, the open fen becomes a woodland within a few years. During the 20th century most of the fens were drained and reclaimed for agricultural use. De Weerribben (3600 ha), now a nature reserve, is one of the remaining fen areas in the north of The Netherlands (6 <sup>o</SUP>0 <sup>'</SUP>E and 52 <sup>o</SUP>45 <sup>'</SUP>N).</p><p>Hydrology strongly influences the species composition in De Weerribben. Water loss caused by this infiltration to the surrounding polders that have a lower water table and by evapotranspiration is compensated for by an influx of surface water, precipitation and (locally) by irrigation. This influx creates a complex of gradients from surface water dominance to rainwater dominance.</p><H3>Remote sensing</H3><p>False colour aerial photographs contain detailed information that can be extracted by an interpreter with good field knowledge. The best and most objective combination of methods was used to derive significant information from the photographs without relying too much on the skill of an interpreter. Analogue photo interpretation was suitable to map water, peat baulks, open fen and woodland because they were easily recognized thanks to their contrasting reflectance, texture and sharp boundaries. These classes were used for stratifying the landscape. Within the strata digital image processing was used to derive information on gradients. Interpretation based on expert knowledge of the spectral values coincidence with differences in biomass of the vegetation and wetness of the floating raft.</p><p>Vegetation scientists and nature management organizations are mainly interested in species composition. Although species composition and reflectance are both characteristics of a vegetation type, it was not possible to map the desired vegetation types of the entire area solely with aerial photographs. The vegetation types mapped in the field are based on species composition and structural differences that are indicative of environmental conditions to a certain extent. They were grouped into vegetation structure types indicative of differences in biomass, wetness and vegetation management. The reliability and accuracy of the remote sensing classification were determined as an 'indication' of the ecological significance of the spectral classes. It could be concluded that the spectral classes corresponded reasonably well with the grouped vegetation types of the vegetation map. Subsequently, the results of the remote sensing interpretation were used to model hydrological isolation and to predict species distribution.</p><H3>Hydrological isolation in a GIS environment to predict plant species distribution</H3><p>Field information on base status and nutrient status was only available for a few selected sample points in De Weerribben. Information on water chemistry covering the entire area was, therefore, obtained by modelling hydrological isolation spatially. The water balance and Darcy's law were used to define a spatial mathematical model for hydrological isolation. A GIS was used determine topological relations and data integration. The variables input into this model were: precipitation, infiltration, evapotranspiration, permeability, distance to the surface water and hinterland area. Permeability values were obtained by reclassifying the raft thickness classes of the soil map on the basis of literature. Average values for precipitation, infiltration and evapotranspiration were used as input constants because the spatial variation of these variables was not known. The results of the remote sensing interpretation were used as hydrological source (watercourses) and hydrological barriers (peat baulks). Wetness was assumed to be a hydrological short cut, decreasing the influence of the hydrological isolation model. A wet site received surface water by irrigation or flooding instead of an influx through the floating raft.</p><p>The hydrological isolation was used to predict the species distribution. Two plant species indicative of opposite environmental conditions in relation to base status were selected to model species distribution: <em>Scorpidium scorpioides</em> (Hedw.) Limpr and <em>Erica tetralix</em> L. <em>Scorpidium</em> is a rare moss characteristic of base-rich conditions and an early stage of terrestrialization. <em>Erica</em> is a dwarf shrub that is not very rare. It is indicative of base-poor conditions and an advanced stage of terrestrialization.</p><p>Regression analysis was used to determine how <em>Erica</em> and <em>Scorpidium</em> are related to environmental variables and to predict their occurrence. The regression analysis was adapted to take account of the specific conditions of this study. A major problem was 'missing absences' on the point distribution maps of the plant species, i.e. points representing the absence of a species had not been recorded. These absences, which were necessary to apply logit regression, were obtained by generating random points. The distribution of absence points had to be representative of the area of all site factor class combinations, to prove that species distribution is not evenly distributed over all classes. Therefore, there had to be very many such points. As a result, the predicted probabilities of occurrence were relative instead of absolute, because they depended on the number of random points.</p><p>Environmental variables that appeared to have a statistical significant effect on the occurrence of either species agreed well with the environmental needs of these species reported in literature. Hydrological isolation significantly explained the species occurrence. It can be concluded that the remote sensing and GIS techniques turned out to be very suitable for determining hydrological isolation to identify potential habitat for plant species; information can be used to optimize field sampling, for management planning and evaluation, and in scenario studies.</p>
Radar for rain forest : a monitoring system for land cover change in the Colombian Amazon
Bijker, W. - \ 1997
Agricultural University. Promotor(en): R.A. Feddes; W. van Wijngaarden; D.H. Hoekman. - Enschede : ITC - ISBN 9789061641391 - 192
remote sensing - radar - technieken - tropische regenbossen - vegetatie - bosbouw - luchtkarteringen - toepassingen - colombia - techniques - tropical rain forests - vegetation - forestry - aerial surveys - applications
Radar remote sensing to support tropical forest management
Sanden, J.J. van der - \ 1997
Agricultural University. Promotor(en): R.A. Feddes; R.A.A. Oldeman; D.H. Hoekman. - S.l. : S.n. - ISBN 9789054857785 - 330
bosbouw - remote sensing - luchtkarteringen - tropen - bosbedrijfsvoering - planning - tropische regenbossen - vegetatie - toepassingen - forestry - aerial surveys - tropics - forest management - tropical rain forests - vegetation - applications
<p>This text describes an investigation into the potential of radar remote sensing for application to tropical forest management. The information content of various radar images is compared and assessed with regard to the information requirements of parties involved in tropical forest management at the global, national and local spatial levels. The study distinguishes between the use of radar remote sensing for application to forest resource assessment and forest resource monitoring. Both assessment and monitoring are essential components of procedures for sustainable forest management. The radar data studied are of tropical forest areas near the township of Mabura Hill in Guyana and the city of San José del Guaviare in Colombia. Mabura Hill is comprised of differing intact, primary forest types and forests that have been subjected to industrial selective logging. San José del Guaviare, on the other hand, is characterised by the presence of secondary forests and a variety of non-forest cover types. The available radar data set includes high resolution airborne radar images with differing wavelengths (i.e. X-, C-, L- and P-band) and polarizations, time-series images acquired by the first European remote sensing satellite ERS-1 and a collection of low altitude, nadir-looking, X-band scatterometer measurements.<p>The study makes use of three fundamentally different information sources from the radar return signal: its strength or backscatter, polarization and phase, and spatial variability or texture. Results show that backscatter values computed from L- and P-band radar data and textural attributes computed from high resolution X- and C-band radar data make modest to good and complementary bases for region-based classification of tropical land cover at the level of primary forest types. Textural attributes and backscatter values computed per region from mono-temporal ERS-1 images make modest bases for classifying at the levels of primary forest, logged-over forest, secondary forest and non- forest and poor bases for classifying at the level of primary forest types. Roads are usually the most easily observable indicators of foregoing and/or forthcoming (selective) logging and other human activities in ERS-1 images. Detection of change in road networks by means of ERS-1 images would make a good first step in forest resource monitoring at the national spatial level, in particular. Textural attributes enable the ranking of forest types according to the degree of canopy roughness. Specific textural attributes also allow for quantification of canopy architectural properties. Despite differences in measurement scale, the canopy roughness of the land cover types studied was found to appear similarly in the texture of the available spaceborne and short wavelength airborne radar images.
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