bluuebunny/crossref_metadata_2025 huggingface dataset:
Pedagogische ondersteuning en de spilfunctie van het CJG. Uitdagingen voor gemeenten en professionals
Authors: Distelbrink Marjolein , Pels Trees
Published: June 2016

Samenvatting

Nederlandse Gemeenten hebben de taak ouders en jeugdigen te bereiken
met laagdrempelige opvoed- en opgroeisteun. Wat zijn uitdagingen die ze
daarbij tegenkomen? Hoe ontwikkelt zich het Centrum voor Jeugd en Gezin
(CJG), dat hierin een centrale rol dient te spelen? In dit artikel bespreken
we bevindingen uit een praktijkgericht onderzoek naar de ontwikkeling
van het CJG in Amsterdam. Drie verbeterpunten lijken cruciaal voor het
functioneren van het CJG, punten die in de praktijk echter ook dilemma’s
opleveren: het ontwikkelen van een visie op de pedagogische opdracht van
het CJG, laagdrempelig werken en een structurele samenwerking met het
voorveld van mensen en organisaties die dichtbij de gezinnen en jeugdigen
staan. Juist door explicitering van en discussie over uitgangspunten kan
het CJG zijn spilfunctie beter waarmaken.
De ontwikkeling van probleemgedrag bij pleegkinderen: een Vlaams longitudinaal onderzoek
Authors: Vanderfaeillie Johan , Van Holen Frank , De Maeyer Skrallan , Vanschoonlandt Femke , Andries Caroline
Published: June 2016

Samenvatting

De meeste pleegkinderen hebben gedragsproblemen. De verwachting bestaat
dikwijls dat het probleemgedrag zal afnemen als gevolg van de pleegzorgplaatsing.
In de meeste studies neemt het probleemgedrag echter toe
of blijft het stabiel. Onderzoek naar de ontwikkeling van probleemgedrag
bij pleegkinderen is beperkt. In dit artikel rapporteren we over een longitudinaal
onderzoek bij 49 pleegkinderen naar het verband van globale, contextuele,
familiale en kindfactoren met een toename of een afname van het
probleemgedrag. Na twee jaar hadden 18 pleegkinderen meer, 23 pleegkinderen
evenveel en 8 pleegkinderen minder probleemgedrag. Een toename
was voornamelijk geassocieerd met het gebruik van negatieve opvoedingsstrategieën
door de pleegmoeders. Een afname hield verband met meer ondersteunende
opvoeding. Ondersteuning van pleegouders met het oog op
een vermindering van het gebruik van negatieve opvoedingsstrategieën en
een versterking van de ondersteunende opvoeding zou kunnen bijdragen
aan een vermindering van het probleemgedrag bij pleegkinderen.
Thuisonderwijs in Nederland en Vlaanderen: een review
Authors: Blok Henk , Sperling Joke
Published: June 2016

Samenvatting

Zowel in Nederland als in Vlaanderen is er onder ouders een groeiende belangstelling
voor thuisonderwijs. In deze review wordt thuisonderwijs van
twee zijden belicht, zowel wat betreft de juridische inbedding in Nederland
en Vlaanderen als ook wat betreft de verschijningsvorm. Waar thuisonderwijs
in Vlaanderen inmiddels juridisch is ingekaderd, heeft het in Nederland
geen wettelijke status. Ook wat betreft de verschijningsvorm blijken er
verschillen te zijn tussen Nederland en Vlaanderen. Waar Nederlandse ouders
levensbeschouwelijke motieven aanvoeren, tellen voor Vlaamse ouders
vooral pedagogische motieven om tot thuisonderwijs over te gaan. Over
de manier waarop thuisonderwijs vorm krijgt, bestaan nog veel vragen. De
review eindigt met een bespreking van de vraag of thuisonderwijs ook in
Nederland een wettelijke basis zou moeten krijgen. Ook wordt een tweetal
onderzoekslijnen voor vervolgonderzoek aangeduid. Vervolgonderzoek
zou zich vooral moeten richten op de condities waaronder thuisonderwijs
effectief is.
Niet elk kind is ontvankelijk voor vroegtijdige stimuleringsprogramma’s. De invloed van onderliggende factoren van schoolrijpheid in relatie tot de voor- en vroegschoolse educatie
Authors: Tavecchio Louis , Oostdam Ron
Published: June 2016

Samenvatting

De afgelopen vijftien jaar zijn in Nederland diverse studies verricht naar de
uitvoering en effectiviteit van programma’s op het gebied van de voor- en
vroegschoolse educatie (VVE). De daarmee tot nu toe behaalde resultaten
zijn teleurstellend. Ter verklaring voor het uitblijven van effecten is in de
onderzoeksliteratuur onder meer herhaaldelijk gewezen op het belang
van een goede implementatie en monitoring van het programma, op het
relatief open karakter van sommige programma’s waardoor enorm veel
variatie in de uitvoering ontstaat, en op het probleem om in alle opzichten
goede vergelijkingsgroepen te vormen. Naast deze verklaringen wordt in
dit artikel gewezen op een aantal in Nederland nog te weinig onderkende
en onderzochte verklarende factoren. Het gaat daarbij om belangrijke
variabelen in relatie tot schoolrijpheid (readiness for school), te weten de
kwaliteit van leidster/leerkracht-kindinteracties, gedragsmatige aspecten
als aanpassings- en gedragsproblemen, en het belang van gezinsstructuur
en gezinsopvoeding.
Een kind als geschenk of als handelswaar? Commercieel draagmoederschap en (het gevaar van) commodificatie
Authors: Hoencamp Marloes , de Ruyter Doret
Published: June 2016

Samenvatting

Commercieel draagmoederschap is één van de reproductietechnieken die het
voor echtparen met vruchtbaarheidsproblemen mogelijk maakt hun kinderwens
in vervulling te zien gaan. Deze techniek is echter niet zonder gevolgen
voor het kind. Er kan commodificatie optreden, zowel in smalle zin: het kind
wordt een product dat gekocht wordt, als in brede zin: het beeld van het kind
als geschenk dat niet gemaakt wordt naar de wensen van ouders lijkt te worden
uitgesloten. De vraag die daarbij kan worden gesteld is of commodificatie van
het kind ethisch te aanvaarden is. Naar een ethische rechtvaardiging van commodificatie
kan worden gezocht middels het reflectief equilibrium. Commodificatie
en commercieel draagmoederschap zijn alleen gerechtvaardigd wanneer
het kind als goed in zichzelf wordt beschouwd.
Informatiegebruik in verantwoordingsgerichte en schoolontwikkelingsgerichte onderwijssystemen: een Nederlands-Vlaams perspectief
Authors: Van Gasse Roos , Vanhoof Jan , de Vos Willem
Published: June 2016

Samenvatting

Wereldwijd wordt hoe langer hoe meer belang gehecht aan
informatiegebruik in scholen. Hoewel verschillen in het informatiegebruik
van scholen in onderzoek vaak gerelateerd worden aan
een verantwoordingsgericht of schoolontwikkelingsgericht onderwijssysteem,
is onderzoek dat informatiegebruik in verschillende onderwijssystemen
diepgaand beschrijft en vergelijkt schaars. In deze studie onderzoeken
we gelijkenissen en verschillen in het informatiegebruik van schoolleiders
binnen een verantwoordingsgericht en een schoolontwikkelingsgericht
onderwijssysteem, respectievelijk Nederland en Vlaanderen. De resultaten
wijzen uit dat schoolleiders uit beide onderwijssystemen andere verwachtingen
percipiëren inzake informatiegebruik, andere soorten informatie
gebruiken en ook verschillen in de manieren waarop zij informatie gebruiken.
Een opvallende vaststelling is dat sterkere verwachtingen naar verantwoording
niet noodzakelijk in negatieve zin wegen op het schoolontwikkelingsgericht
informatiegebruik van schoolleiders.
100 jaar leerplicht in België: en nu de kleuters?
Authors: Van Laere Katrien , VandenBroeck Michel
Published: June 2016

Samenvatting

Honderd jaar na de invoering van de leerplicht discussiëren Belgische en
Vlaamse beleidsmakers nog steeds over de aanvang van die leerplicht. Net
als in de jaren 1960 en 1970 wensen sommige beleidsmakers de leerplicht
te verlagen om gelijke kansen aan elk kind te bieden. Met kan echter zich
afvragen waarom meer onderwijs de oplossing zou zijn, indien we vaststellen
dat het onderwijssysteem de ongelijkheid van kansen reproduceert. We
schetsen een historisch overzicht van deze discussie en vanuit die analyse
plaatsen we een kritische kanttekening bij de manier waarop het IVRK het
recht op leren vertaalt in een schoolplicht. We zien immers een spanning
tussen het recht op leren (artikel 28) en het recht op zorg, welbevinden en
het belang van het kind, maar ook met het respect voor de visie van ouders
(artikel 5).
Recht op onderwijs voor minderjarige vluchtelingen: wat als de toekomst niet in België ligt?
Authors: Verhaeghe Floor , Derluyn Ilse
Published: June 2016

Samenvatting

Alle minderjarigen die in België verblijven hebben recht op onderwijs. Een
analyse van beleidsdocumenten laat zien dat de jongeren ondersteunen om
een toekomst op te bouwen in België een van de belangrijkste doelen is die
de overheid stelt aan het onderwijs aan jonge vluchtelingen. Ook in onderzoek
met jonge vluchtelingen wordt duidelijk dat de kansen die onderwijs
kan bieden om een beter leven en een betere toekomst op te bouwen voor
hen het belangrijkste aspect zijn van het recht op onderwijs. Dit staat in
schril contrast met het grote aantal jongeren dat de beslissing krijgt dat ze
niet in België kunnen blijven en hun toekomst elders zullen moeten uitbouwen.
Het spanningsveld tussen het recht op onderwijs enerzijds en het
huidige migratiebeleid anderzijds, dat teruggebracht kan worden naar het
spanningsveld kind versus vluchteling, is over het algemeen onderhevig
aan ‘silencing’ in het onderwijsbeleid. ‘Silencing’ van dit spanningsveld
plaatst jonge vluchtelingen en hun leerkrachten in een ‘limbo’: enerzijds
worden ze aangemoedigd om een toekomst in België op te bouwen, anderzijds
zal die toekomst voor velen van hen niet in België liggen. We stellen
hier dat de bevoegde overheidsinstanties dit spanningsveld expliciet moeten
erkennen in hun onderwijsbeleid, omdat dit het emotionele welzijn
van de kinderen kan versterken en de mogelijkheden van leerkrachten om
hen te ondersteunen kan vergroten.
Harry Potter zonder toverstaf verliest zijn magie – over de rechten van uit huis geplaatste kinderen
Authors: Van Zon Kartica
Published: June 2016

Samenvatting

Kinderen die niet bij hun eigen ouders kunnen opgroeien hebben recht op
bijzondere bescherming en bijstand, zo is bepaald in het Verdrag inzake
de Rechten van het Kind. Wat deze bijzondere bescherming en bijstand
precies inhoudt, is lange tijd niet duidelijk geweest. De laatste jaren is daar
verandering in gekomen. Dit artikel biedt allereerst een staalkaart van de
invulling van het begrip bijzondere bescherming en bijstand in internationaal
juridische documenten. Daarna wordt betoogd dat een concretisering
van de verplichtingen van Staten ten aanzien van kinderen in alternatieve
zorg weliswaar nuttig is, maar slechts betekenis krijgt wanneer kinderen
ook daadwerkelijk de mogelijkheid hebben om hun recht af te dwingen.
Het artikel sluit af met de aanknopingspunten die het internationale recht
biedt om de rechtstoegang voor kinderen in alternatieve zorg te verbeteren.
Burgerschapsvorming anders: een pleidooi voor zakelijk onderwijs
Authors: van der Ploeg Piet
Published: June 2016

Samenvatting

Er zijn sterk verschillende opvattingen over wat goed burgerschap is. Het onderwijs
hoort met deze verscheidenheid rekening te houden. Het Europese
beleid aangaande burgerschapsvorming propageert evenwel onderwijs dat
zich richt naar een beperkt en exclusief normatief kader, een hybride van
de liberale en de republikeinse burgerschapsideologie. Voor het Nederlandse
beleid geldt nagenoeg hetzelfde. In dit artikel wordt de eenzijdigheid van
het Europese en Nederlandse beleid geïllustreerd en bekritiseerd. Vervolgens
wordt nagegaan of het anders kan: of burgerschapsvorming anders begrepen
kan worden en of burgerschapsvorming anders ingericht kan worden,
zodanig dat in het onderwijs wel voldoende recht gedaan wordt aan de
diversiteit aan opvattingen over wat goed burgerschap is.
Een streep door discriminatie?
Authors: Zwiep Channah
Published: June 2016

Samenvatting

Seksuele opvoeding is een belangrijk maar beladen thema
in de kinderopvang. Hoe geven mannelijke pedagogisch
medewerkers hieraan vorm en welke knelpunten ervaren
zij hierbij? Aan de hand van een topiclijst zijn mannelijke
medewerkers in de kinderopvang (n = 37) geïnterviewd.
Uit de resultaten blijkt dat de mannelijke pedagogisch medewerkers
de seksuele ontwikkeling van kinderen zoveel
mogelijk professioneel begeleiden. Zij beantwoorden vragen van kinderen
en corrigeren seksueel getint gedrag indien nodig. De mannelijke pedagogisch
medewerkers zijn zich sinds de Amsterdamse zedenzaak extra bewust
van hun kwetsbare positie. Zij vermijden ‘risicovolle’ situaties, maar vinden
tegelijkertijd dat lichamelijkheid onvermijdelijk is in hun omgang met kinderen.
De mannelijke pedagogisch medewerkers hebben behoefte aan pedagogisch
beleid en een praktische werkwijze rondom seksuele opvoeding.
Bulk density and its connection to other microphysical properties of snow as observed in Southern Finland
Authors: Tiira Jussi , Moisseev Dmitri N. , von Lerber Annakaisa , Ori Davide , Tokay Ali , Bliven Larry F. , Petersen Walter
Published: June 2016

Abstract. In this study measurements collected during winters 2013/2014 and 2014/2015 at the University of Helsinki measurement station in Hyytiälä are used to investigate connections between snow bulk density, particle fall velocity and parameters of the particle size distribution (PSD). The bulk density of snow is derived from measurements of particle fall velocity and PSD, provided by a particle video imager, and weighing gauge measurements of precipitation rate. Validity of the retrieved density values is checked against snow depth measurements. A relation retrieved for bulk density and median volume diameter is in general agreement with previous studies, but observed to vary significantly from one winter to the other. From these observations, characteristic mass-dimensional relations of snow are retrieved. For snow rates more than 0.2 mm h−1, a correlation between the intercept parameter of normalized gamma PSD and median volume diameter was observed .
The metabolic response of thecosome pteropods from the North Atlantic and North Pacific Oceans to high CO2 and low O2
Authors: Maas Amy E. , Lawson Gareth L. , Wang Zhaohui A.
Published: June 2016

Abstract. As anthropogenic activities, notably the burning of fossil fuels, increase carbon dioxide (CO2) and result in a decrease in oxygen (O2) concentrations in the ocean system, it becomes important to understand how different populations of marine animals will respond. Water that is naturally lower in pH, with a high concentration of carbon dioxide (hypercapnia) and a low concentration of oxygen, occurs at shallow depths (200–500 m) in the North Pacific Ocean, whereas similar conditions are absent throughout the upper water column in the North Atlantic. This contrasting hydrography provides a natural experiment to explore whether differences in environment cause populations of cosmopolitan pelagic calcifiers, specifically the aragonitic-shelled pteropods, to have a different physiological response when exposed to hypercapnia and low O2. Using closed-chamber end-point respiration experiments, eight species of pteropods from the two ocean basins were exposed to high CO2 (~ 800 µatm) while six species were also exposed to moderately low O2 (10 %, or ~ 130 µmol kg−1) and a combined treatment of low O2/high CO2. None of the species tested showed a change in metabolic rate in response to high CO2 alone. Of those species tested for an effect of O2, only Limacina retroversa from the Atlantic showed a response to the combined treatment, resulting in a reduction in metabolic rate. Our results suggest that pteropods have mechanisms for coping with short-term CO2 exposure and suggest that there can be interactive effects between stressors on the physiology of these open ocean organisms that correlate with natural exposure to low O2 and high CO2; these are considerations that should be taken into account in projections of organismal sensitivity to future ocean conditions.
CONVEX IMAGE ORIENTATION FROM RELATIVE ORIENTATIONS
Authors: Reich M. , Heipke C.
Published: June 2016

Abstract. In this paper we propose a novel workflow for the estimation of global image orientations given relative orientations between pairs of overlapping images. Our approach is convex and independent on initial values. First, global rotations are estimated in a relaxed semidefinite program (SDP) and refined in an iterative least squares adjustment in the tangent space of SO(3). A critical aspect is the handling of outliers in the relative orientations. We present a novel heuristic graph based approach for filtering the relative rotations that outperforms state-of-the-art robust rotation averaging algorithms. In a second part we make use of point-observations, tracked over a set of overlapping images and formulate a linear homogeneous system of equations to transfer the scale information between triplets of images, using estimated global rotations and relative translation directions. The final step consists of refining the orientation parameters in a robust bundle adjustment. The proposed approach handles outliers in the homologous points and relative orientations in every step of the processing chain. We demonstrate the robustness of the procedure on synthetic data. Moreover, the performance of our approach is illustrated on real world benchmark data.
PHOTOGRAMMETRIC ACCURACY AND MODELING OF ROLLING SHUTTER CAMERAS
Authors: Ye W. , Qiao G. , Kong F. , Guo S. , Ma X. , Tong X. , Li R.
Published: June 2016

Abstract. Global climate change is one of the major challenges that all nations are commonly facing. Long-term observations of the Antarctic ice sheet have been playing a critical role in quantitatively estimating and predicting effects resulting from the global changes. The film-based ARGON reconnaissance imagery provides a remarkable data source for studying the Antarctic ice-sheet in 1960s, thus greatly extending the time period of Antarctica surface observations. To deal with the low-quality images and the unavailability of camera poses, a systematic photogrammetric approach is proposed to reconstruct the interior and exterior orientation information for further glacial mapping applications, including ice flow velocity mapping and mass balance estimation. Some noteworthy details while performing geometric modelling using the ARGON images were introduced, including methods and results for handling specific effects of film deformation, damaged or missing fiducial marks and calibration report, automatic fiducial mark detection, control point selection through Antarctic shadow and ice surface terrain analysis, and others. Several sites in East Antarctica were tested. As an example, four images in the Byrd glacier region were used to assess the accuracy of the geometric modelling. A digital elevation model (DEM) and an orthophoto map of Byrd glacier were generated. The accuracy of the ground positions estimated by using independent check points is within one nominal pixel of 140 m of ARGON imagery. Furthermore, a number of significant features, such as ice flow velocity and regional change patterns, will be extracted and analysed.
URBAN TREE CLASSIFICATION USING FULL-WAVEFORM AIRBORNE LASER SCANNING
Authors: Koma Zs. , Koenig K. , Höfle B.
Published: June 2016

Abstract. Vegetation mapping in urban environments plays an important role in biological research and urban management. Airborne laser scanning provides detailed 3D geodata, which allows to classify single trees into different taxa. Until now, research dealing with tree classification focused on forest environments. This study investigates the object-based classification of urban trees at taxonomic family level, using full-waveform airborne laser scanning data captured in the city centre of Vienna (Austria). The data set is characterised by a variety of taxa, including deciduous trees (beeches, mallows, plane trees and soapberries) and the coniferous pine species. A workflow for tree object classification is presented using geometric and radiometric features. The derived features are related to point density, crown shape and radiometric characteristics. For the derivation of crown features, a prior detection of the crown base is performed. The effects of interfering objects (e.g. fences and cars which are typical in urban areas) on the feature characteristics and the subsequent classification accuracy are investigated. The applicability of the features is evaluated by Random Forest classification and exploratory analysis. The most reliable classification is achieved by using the combination of geometric and radiometric features, resulting in 87.5% overall accuracy. By using radiometric features only, a reliable classification with accuracy of 86.3% can be achieved. The influence of interfering objects on feature characteristics is identified, in particular for the radiometric features. The results indicate the potential of using radiometric features in urban tree classification and show its limitations due to anthropogenic influences at the same time.
ULS LiDAR SUPPORTED ANALYSES OF LASER BEAM PENETRATION FROM DIFFERENT ALS SYSTEMS INTO VEGETATION
Authors: Wieser M. , Hollaus M. , Mandlburger G. , Glira P. , Pfeifer N.
Published: June 2016

Abstract. This study analyses the underestimation of tree and shrub heights for different airborne laser scanner systems and point cloud distribution within the vegetation column. Reference data was produced by a novel UAV-borne laser scanning (ULS) with a high point density in the complete vegetation column. With its physical parameters (e.g. footprint) and its relative accuracy within the block as stated in Section 2.2 the reference data is supposed to be highly suitable to detect the highest point of the vegetation. An airborne topographic (ALS) and topo-bathymetric (ALB) system were investigated. All data was collected in a period of one month in leaf-off condition, while the dominant tree species in the study area are deciduous trees. By robustly estimating the highest 3d vegetation point of each laser system the underestimation of the vegetation height was examined in respect to the ULS reference data. This resulted in a higher under-estimation of the airborne topographic system with 0.60 m (trees) and 0.55 m (shrubs) than for the topo-bathymetric system 0.30 m (trees) and 0.40 m (shrubs). The degree of the underestimation depends on structural characteristics of the vegetation itself and physical specification of the laser system.
AUTOMATIC EXTRACTION OF DTM FROM LOW RESOLUTION DSM BY TWOSTEPS SEMI-GLOBAL FILTERING
Authors: Zhang Yanfeng , Zhang Yongjun , Zhang Yi , Li Xin
Published: June 2016

Abstract. Automatically extracting DTM from DSM or LiDAR data by distinguishing non-ground points from ground points is an important issue. Many algorithms for this issue are developed, however, most of them are targeted at processing dense LiDAR data, and lack the ability of getting DTM from low resolution DSM. This is caused by the decrease of distinction on elevation variation between steep terrains and surface objects. In this paper, a method called two-steps semi-global filtering (TSGF) is proposed to extract DTM from low resolution DSM. Firstly, the DSM slope map is calculated and smoothed by SGF (semi-global filtering), which is then binarized and used as the mask of flat terrains. Secondly, the DSM is segmented with the restriction of the flat terrains mask. Lastly, each segment is filtered with semi-global algorithm in order to remove non-ground points, which will produce the final DTM. The first SGF is based on global distribution characteristic of large slope, which distinguishes steep terrains and flat terrains. The second SGF is used to filter non-ground points on DSM within flat terrain segments. Therefore, by two steps SGF non-ground points are removed robustly, while shape of steep terrains is kept. Experiments on DSM generated by ZY3 imagery with resolution of 10-30m demonstrate the effectiveness of the proposed method.
RECTIFICATION AND ROBUST MATCHING USING ORIENTED IMAGE TRIPLETS FOR MINIMALLY INVASIVE SURGERY
Authors: Conen N. , Jepping C. , Luhmann T. , Maas H.-G.
Published: June 2016

Abstract. Stereo endoscopes for minimally invasive surgery have been available on the market for several years and are well established in some areas. In practice, they offer a stereoscopic view to the surgeon but are not yet intended for 3D measurements. However, using current knowledge about the camera system and the difficult conditions in object space, it is possible to reconstruct a highly accurate surface model of the current endoscopic view. In particular for medical interventions, a highly reliable point cloud and real-time computation are required. To obtain good reliability, a miniaturised trinocular camera system is introduced that reduces the amount of outliers. To reduce computation time, an approach for generation of rectified image triplets and their corresponding interior and exterior camera parameters has been developed. With these modified and parameterised images it is possible to directly process 3D measurements in object space. Accordingly, an efficient semi-global optimisation is implemented by the authors. In this paper the special camera system, the rectification approach and the applied methodology of matching in rectified image triplets are explained. Finally, first results are presented. In conclusion, the trinocular camera system provides more reliable point clouds than a binocular one, especially for areas with repetitive or poor texture. Currently, the benefit of the third camera is not as great as desired.
FAST AND RESISTANT PROCRUSTEAN BUNDLE ADJUSTMENT
Authors: Fusiello Andrea , Crosilla Fabio
Published: June 2016

Abstract. In a recent paper (Fusiello and Crosilla, 2015) a Procrustean formulation of the bundle block adjustment has been presented, with a solution based on alternating least squares. This paper improves on it in two respects: it introduces a faster iterative scheme that minimizes the same cost function, thereby achieving the same accuracy, and makes the method resistant to rogue measures through iteratively reweighted least-squares. Empirical results confirm the effectiveness of these enhancements.
TOWARDS COMPLETE, GEO-REFERENCED 3D MODELS FROM CROWD-SOURCED AMATEUR IMAGES
Authors: Hartmann W. , Havlena M. , Schindler K.
Published: June 2016

Abstract. Despite a lot of recent research, photogrammetric reconstruction from crowd-sourced imagery is plagued by a number of recurrent problems. (i) The resulting models are chronically incomplete, because even touristic landmarks are photographed mostly from a few “canonical” viewpoints. (ii) Man-made constructions tend to exhibit repetitive structure and rotational symmetries, which lead to gross errors in the 3D reconstruction and aggravate the problem of incomplete reconstruction. (iii) The models are normally not geo-referenced. In this paper, we investigate the possibility of using sparse GNSS geo-tags from digital cameras to address these issues and push the boundaries of crowd-sourced photogrammetry. A small proportion of the images in Internet collections (≈ 10 %) do possess geo-tags. While the individual geo-tags are very inaccurate, they nevertheless can help to address the problems above. By providing approximate geo-reference for partial reconstructions they make it possible to fuse those pieces into more complete models; the capability to fuse partial reconstruction opens up the possibility to be more restrictive in the matching phase and avoid errors due to repetitive structure; and collectively, the redundant set of low-quality geo-tags can provide reasonably accurate absolute geo-reference. We show that even few, noisy geo-tags can help to improve architectural models, compared to puristic structure-from-motion only based on image correspondence.
RECONSTRUCTING WHITE WALLS: MULTI-VIEW, MULTI-SHOT 3D RECONSTRUCTION OF TEXTURELESS SURFACES
Authors: Ley Andreas , Hänsch Ronny , Hellwich Olaf
Published: June 2016

Abstract. The reconstruction of the 3D geometry of a scene based on image sequences has been a very active field of research for decades. Nevertheless, there are still existing challenges in particular for homogeneous parts of objects. This paper proposes a solution to enhance the 3D reconstruction of weakly-textured surfaces by using standard cameras as well as a standard multi-view stereo pipeline. The underlying idea of the proposed method is based on improving the signal-to-noise ratio in weakly-textured regions while adaptively amplifying the local contrast to make better use of the limited numerical range in 8-bit images. Based on this premise, multiple shots per viewpoint are used to suppress statistically uncorrelated noise and enhance low-contrast texture. By only changing the image acquisition and adding a preprocessing step, a tremendous increase of up to 300% in completeness of the 3D reconstruction is achieved.
EXTENSION AND EVALUATION OF THE AGAST FEATURE DETECTOR
Authors: Zhang Hongmou , Wohlfeil Jürgen , Grießbach Denis
Published: June 2016

Abstract. Vision-aided inertial navigation is a navigation method which combines inertial navigation with computer vision techniques. It can provide a six degrees of freedom navigation solution from passive measurements without external referencing (e.g. GPS). Thus, it can operate in unknown environments without any prior knowledge. Such a system, called IPS (Integrated Positioning System) is developed by the German Aerospace Center (DLR). For optical navigation applications, a reliable and efficient feature detector is a crucial component. With the publication of AGAST, a new feature detector has been presented, which is faster than other feature detectors. To apply AGAST to optical navigation applications, we propose several methods to improve its performance. Based on a new non-maximum suppression algorithm, automatic threshold adaption algorithm in combination with an image split method, the optimized AGAST provides higher reliability and efficiency than the original implementation using the Kanade Lucas Tomasi (KLT) feature detector. Finally, we compare the performance of the optimized AGAST with the KLT feature detector in the context of IPS. The presented approach is tested using real data from typical indoor scenes, evaluated on the accuracy of the navigation solution. The comparison demonstrates a significant performance improvement achieved by the optimized AGAST.
VALIDATION OF "AW3D" GLOBAL DSM GENERATED FROM ALOS PRISM
Authors: Takaku Junichi , Tadono Takeo , Tsutsui Ken , Ichikawa Mayumi
Published: June 2016

Abstract. Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), one of onboard sensors carried by Advanced Land Observing Satellite (ALOS), was designed to generate worldwide topographic data with its optical stereoscopic observation. It has an exclusive ability to perform a triplet stereo observation which views forward, nadir, and backward along the satellite track in 2.5 m ground resolution, and collected its derived images all over the world during the mission life of the satellite from 2006 through 2011. A new project, which generates global elevation datasets with the image archives, was started in 2014. The data is processed in unprecedented 5 m grid spacing utilizing the original triplet stereo images in 2.5 m resolution. As the number of processed data is growing steadily so that the global land areas are almost covered, a trend of global data qualities became apparent. This paper reports on up-to-date results of the validations for the accuracy of data products as well as the status of data coverage in global areas. The accuracies and error characteristics of datasets are analyzed by the comparison with existing global datasets such as Ice, Cloud, and land Elevation Satellite (ICESat) data, as well as ground control points (GCPs) and the reference Digital Elevation Model (DEM) derived from the airborne Light Detection and Ranging (LiDAR).
DEFINING EARTH DATA BATCH PROCESSING TASKS BY MEANS OF A FLEXIBLE WORKFLOWDESCRIPTION LANGUAGE
Authors: Nandra Constantin , Gorgan Dorian
Published: June 2016

Abstract. This paper aims to present some of the main features of the Workflow Description Language (WorDeL) and demonstrate their usage in defining Earth Data processing tasks. This description language is based on the flexible description of processing tasks as workflows, composed of basic processing operators. This approach allows the language to offer an intuitive way of representing processing tasks, without requiring programming expertise from its users. It also allows its users to employ and integrate existing functionality into their design, thereby reducing the design complexity and development effort of newly defined processing workflows. WorDeL supports the transparent adaptive parallelization of the processing tasks over high performance computation architectures, such as cloud-based solutions. Throughout the paper, we will exemplify this language’s use in creating flexible, reusable and easy-to-understand earth data processing descriptions, with an emphasis on satellite image processing.
COMMERCIAL OFF THE SHELF GROUND CONTROL SUPPORTS CALIBRATION AND CONFLATION FROM GROUND TO SPACE BASED SENSORS
Authors: Danielová M. , Hummel P.
Published: June 2016

Abstract. The need for rapid deployment of aerial and satellite imagery in support of GIS and engineering integration projects require new sources of geodetic control to ensure the accuracy for geospatial projects. In the past, teams of surveyors would need to deploy to project areas to provide targeted or photo identifiable points that are used to provide data for orthorecificaion, QA/QC and calibration for multi-platform sensors. The challenge of integrating street view, UAS, airborne and Space based sensors to produce the common operational picture requires control to tie multiple sources together. Today commercial off the shelf delivery of existing photo identifiable control is increasing the speed of deployment of this data without having to revisit sites over and over again. The presentation will discuss the processes developed by CompassData to build a global library of 40,000 control points available today. International Organization for Standardization (ISO) based processes and initiatives ensure consistent quality of survey data, photo identifiable features selected and meta data to support photogrammetrist, engineers and GIS professionals to quickly deliver projects with better accuracy.
EFFICIENT ORIENTATION AND CALIBRATION OF LARGE AERIAL BLOCKS OF MULTI-CAMERA PLATFORMS
Authors: Karel W. , Ressl C. , Pfeifer N.
Published: June 2016

Abstract. Aerial multi-camera platforms typically incorporate a nadir-looking camera accompanied by further cameras that provide oblique views, potentially resulting in utmost coverage, redundancy, and accuracy even on vertical surfaces. However, issues have remained unresolved with the orientation and calibration of the resulting imagery, to two of which we present feasible solutions. First, as standard feature point descriptors used for the automated matching of homologous points are only invariant to the geometric variations of translation, rotation, and scale, they are not invariant to general changes in perspective. While the deviations from local 2D-similarity transforms may be negligible for corresponding surface patches in vertical views of flat land, they become evident at vertical surfaces, and in oblique views in general. Usage of such similarity-invariant descriptors thus limits the amount of tie points that stabilize the orientation and calibration of oblique views and cameras. To alleviate this problem, we present the positive impact on image connectivity of using a quasi affine-invariant descriptor. Second, no matter which hard- and software are used, at some point, the number of unknowns of a bundle block may be too large to be handled. With multi-camera platforms, these limits are reached even sooner. Adjustment of sub-blocks is sub-optimal, as it complicates data management, and hinders self-calibration. Simply discarding unreliable tie points of low manifold is not an option either, because these points are needed at the block borders and in poorly textured areas. As a remedy, we present a straight-forward method how to considerably reduce the number of tie points and hence unknowns before bundle block adjustment, while preserving orientation and calibration quality.
EVALUATION OF THE MAIN CEOS PSEUDO CALIBRATION SITES USING MODIS BRDF/ALBEDO PRODUCTS
Authors: Kharbouche Said , Muller Jan-Peter
Published: June 2016

Abstract. This work describes our findings about an evaluation of the stability and the consistency of twenty primary PICSs (Pseudo-Invariant Calibration Sites). We present an analysis of 13 years of 8-daily MODIS products of BRDF parameters and white-sky-albedos (WSA) over the shortwave band. This time series of WSA and BRDFs shows the variation of the “stability” varies significantly from site to site. Using a 10x10 km window size over all the sites, the change in of WSA stability is around 4% but the isotropicity, which is an important element in inter-satellite calibration, can vary from 75% to 98%. Moreover, some PICS, especially, Libya-4 which is one of the PICS which is most employed, has significant and relatively fast changes in wintertime. PICS observations of BRDF/albedo shows that the Libya-4 PICS has the best performance but it is not too far from some sites such as Libya-1 and Mali. This study also reveals that Niger-3 PICS has the longest continuous period of high stability per year, and Sudan has the most isotropic surface. These observations have important implications for the use of these sites.
COMPARATIVE ANALYSIS OF DIFFERENT LIDAR SYSTEM CALIBRATION TECHNIQUES
Authors: Miller M. , Habib A.
Published: June 2016

Abstract. With light detection and ranging (LiDAR) now being a crucial tool for engineering products and on the fly spatial analysis, it is necessary for the user community to have standardized calibration methods. The three methods in this study were developed and proven by the Digital Photogrammetry Research Group (DPRG) for airborne LiDAR systems and are as follows; Simplified, Quasi-Rigorous, and Rigorous. In lieu of using expensive control surfaces for calibration, these methods compare overlapping LiDAR strips to estimate the systematic errors. These systematic errors are quantified by these methods and include the lever arm biases, boresight biases, range bias and scan angle scale bias. These three methods comprehensively represent all of the possible flight configurations and data availability and this paper will test the limits of the method with the most assumptions, the simplified calibration, by using data that violates the assumptions it’s math model is based on and compares the results to the quasi-rigorous and rigorous techniques. The overarching goal is to provide a LiDAR system calibration that does not require raw measurements which can be carried out with minimal control and flight lines to reduce costs. This testing is unique because the terrain used for calibration does not contain gable roofs, all other LiDAR system calibration testing and development has been done with terrain containing features with high geometric integrity such as gable roofs.
ESTIMATION OF THE ATMOSPHERIC REFRACTION EFFECT IN AIRBORNE IMAGES USING RADIOSONDE DATA
Authors: Beisl U. , Tempelmann U.
Published: June 2016

Abstract. The influence of the atmospheric refraction on the geometric accuracy of airborne photogrammetric images was already considered in the days of analogue photography. The effect is a function of the varying refractive index on the path from the ground to the image sensor. Therefore the effect depends on the height over ground, the view zenith angle and the atmospheric constituents. It is leading to a gradual increase of the scale towards the borders of the image, i.e. a magnification takes place. Textbooks list a shift of several pixels at the borders of standard wide angle images. As it was the necessity of that time when images could only be acquired at good weather conditions, the effect was calculated using standard atmospheres for good atmospheric conditions, leading to simple empirical formulas. Often the pixel shift caused by refraction was approximated as linear with height and compensated by an adjustment of the focal length. With the advent of sensitive digital cameras, the image dynamics allows for capturing images at adverse weather conditions. So the influence of the atmospheric profiles on the geometric accuracy of the images has to be investigated and the validity of the standard correction formulas has to be checked. This paper compares the results from the standard formulas by Saastamoinen with the results calculated from a broad selection of atmospheres obtained from radiosonde profile data. The geometric deviation is calculated by numerical integration of the refractive index as a function of the height using the refractive index formula by Ciddor. It turns out that the effect of different atmospheric profiles (including inversion situations) is generally small compared to the overall effect except at low camera heights. But there the absolute deviation is small. Since the necessary atmospheric profile data are often not readily available for airborne images a formula proposed by Saastamoinen is verified that uses only camera height, the pressure at the ground and the camera level, and the temperature at the camera level.
ACCURACY COMPARISON OF VHR SYSTEMATIC-ORTHO SATELLITE IMAGERIES AGAINST VHR ORTHORECTIFIED IMAGERIES USING GCP
Authors: Widyaningrum E. , Fajari M. , Octariady J.
Published: June 2016

Abstract. The Very High Resolution (VHR) satellite imageries such us Pleiades, WorldView-2, GeoEye-1 used for precise mapping purpose must be corrected from any distortion to achieve the expected accuracy. Orthorectification is performed to eliminate geometric errors of the VHR satellite imageries. Orthorectification requires main input data such as Digital Elevation Model (DEM) and Ground Control Point (GCP). The VHR systematic-ortho imageries were generated using SRTM 30m DEM without using any GCP data. The accuracy value differences of VHR systematic-ortho imageries and VHR orthorectified imageries using GCP currently is not exactly defined. This study aimed to identified the accuracy comparison of VHR systematic-ortho imageries against orthorectified imageries using GCP. Orthorectified imageries using GCP created by using Rigorous model. Accuracy evaluation is calculated by using several independent check points.
DEM EXTRACTION FROM WORLDVIEW-3 STEREO-IMAGES AND ACCURACY EVALUATION
Authors: Hu F. , Gao X. M. , Li G.Y. , Li M.
Published: June 2016

Abstract. This paper validates the potentials of Worldview-3 satellite images in large scale topographic mapping, by choosing Worldview-3 along-track stereo-images of Yi Mountain area in Shandong province China for DEM extraction and accuracy evaluation. Firstly, eighteen accurate and evenly-distributed GPS points are collected in field and used as GCPs/check points, the image points of which are accurately measured, and also tie points are extracted from image matching; then, the RFM-based block adjustment to compensate the systematic error in image orientation is carried out and the geo-positioning accuracy is calculated and analysed; next, for the two stereo-pairs of the block, DSMs are separately constructed and mosaicked as an entirety, and also the corresponding DEM is subsequently generated; finally, compared with the selected check points from high-precision airborne LiDAR point cloud covering the same test area, the accuracy of the generated DEM with 2-meter grid spacing is evaluated by the maximum (max.), minimum (min.), mean and standard deviation (std.) values of elevation biases. It is demonstrated that, for Worldview-3 stereo-images used in our research, the planimetric accuracy without GCPs is about 2.16 m (mean error) and 0.55 (std. error), which is superior to the nominal value, while the vertical accuracy is about -1.61 m (mean error) and 0.49 m (std. error); with a small amount of GCPs located in the center and four corners of the test area, the systematic error can be well compensated. The std. value of elevation biases between the generated DEM and the 7256 LiDAR check points are about 0.62 m. If considering the potential uncertainties in the image point measurement, stereo matching and also elevation editing, the accuracy of generating DEM from Worldview-3 stereo-images should be more desirable. Judging from the results, Worldview-3 has the potential for 1:5000 or even larger scale mapping application.
ANALYSIS AND CORRECTION OF SYSTEMATIC HEIGHT MODEL ERRORS
Authors: Jacobsen K.
Published: June 2016

Abstract. The geometry of digital height models (DHM) determined with optical satellite stereo combinations depends upon the image orientation, influenced by the satellite camera, the system calibration and attitude registration. As standard these days the image orientation is available in form of rational polynomial coefficients (RPC). Usually a bias correction of the RPC based on ground control points is required. In most cases the bias correction requires affine transformation, sometimes only shifts, in image or object space. For some satellites and some cases, as caused by small base length, such an image orientation does not lead to the possible accuracy of height models. As reported e.g. by Yong-hua et al. 2015 and Zhang et al. 2015, especially the Chinese stereo satellite ZiYuan-3 (ZY-3) has a limited calibration accuracy and just an attitude recording of 4 Hz which may not be satisfying. Zhang et al. 2015 tried to improve the attitude based on the color sensor bands of ZY-3, but the color images are not always available as also detailed satellite orientation information. There is a tendency of systematic deformation at a Pléiades tri-stereo combination with small base length. The small base length enlarges small systematic errors to object space. But also in some other satellite stereo combinations systematic height model errors have been detected. The largest influence is the not satisfying leveling of height models, but also low frequency height deformations can be seen. A tilt of the DHM by theory can be eliminated by ground control points (GCP), but often the GCP accuracy and distribution is not optimal, not allowing a correct leveling of the height model. In addition a model deformation at GCP locations may lead to not optimal DHM leveling. Supported by reference height models better accuracy has been reached. As reference height model the Shuttle Radar Topography Mission (SRTM) digital surface model (DSM) or the new AW3D30 DSM, based on ALOS PRISM images, are satisfying. They allow the leveling and correction of low frequency height errors and lead to satisfying correction of the DSM based on optical satellite images. The potential of DHM generation, influence of systematic model deformation and possibilities of improvement has been investigated.
A METHOD FOR SELF-CALIBRATION IN SATELLITE WITH HIGH PRECISION OF SPACE LINEAR ARRAY CAMERA
Authors: Liu Wei , Qian Fangming , Miao Yuzhe , Wang Rongjian
Published: June 2016

Abstract. At present, the on-orbit calibration of the geometric parameters of a space surveying camera is usually processed by data from a ground calibration field after capturing the images. The entire process is very complicated and lengthy and cannot monitor and calibrate the geometric parameters in real time. On the basis of a large number of on-orbit calibrations, we found that owing to the influence of many factors, e.g., weather, it is often difficult to capture images of the ground calibration field. Thus, regular calibration using field data cannot be ensured. This article proposes a real time self-calibration method for a space linear array camera on a satellite using the optical auto collimation principle. A collimating light source and small matrix array CCD devices are installed inside the load system of the satellite; these use the same light path as the linear array camera. We can extract the location changes of the cross marks in the matrix array CCD to determine the real-time variations in the focal length and angle parameters of the linear array camera. The on-orbit status of the camera is rapidly obtained using this method. On one hand, the camera’s change regulation can be mastered accurately and the camera’s attitude can be adjusted in a timely manner to ensure optimal photography; in contrast, self-calibration of the camera aboard the satellite can be realized quickly, which improves the efficiency and reliability of photogrammetric processing.