3D SURVEY FOR TECHNOLOGY TRANSFER: LARGO DA MEMORIA IN SÃO PAULO, BRAZIL

With the broadening of the concept of Cultural Heritage - which now, in addition to great monuments, also includes urban cores, landscapes and intangible manifestations - the possibilities for heritage conservation actions have also expanded. Nowadays, in a globalised world immersed in technologies that are evolving with astonishing rapidity, precisely technological innovation can be an important ally for the enhancement of historic public spaces.On the occasion of the bicentenary of the placement of the existing obelisk in the “Largo da Memória” public space (in the centre of São Paulo), a three-dimensional survey pilot project was carried out in cooperation with local municipality. One of the objectives of this project was to develop an example of “good practices” for the conservation of urban space and a possible benchmark for the use of digital data by local technicians avoiding expansive software and hardware solutions. Thus, the three-dimensional survey of the area helped to evaluate the effectiveness of the optimisation of the integrated procedure, taking into consideration the importance of the public space of the Largo, at the intersection of Xavier de Toledo and Quirino de Andrade streets. Technology transfer actions played an important role within the whole process, enabling further evaluations for the conservation of the place by local authorities.</p

A Pipeline of 3D Scene Reconstruction from Point Clouds

3D technologies are becoming increasingly popular as their applications in industrial, consumer, entertainment, healthcare, education, and governmental increase in number. According to market predictions, the total 3D modeling and mapping market is expected to grow from $1.1 billion in 2013 to$7.7 billion by 2018. Thus, 3D modeling techniques for different data sources are urgently needed. This thesis addresses techniques for automated point cloud classification and the reconstruction of 3D scenes (including terrain models, 3D buildings and 3D road networks). First, georeferenced binary image processing techniques were developed for various point cloud classifications. Second, robust methods for the pipeline from the original point cloud to 3D model construction were proposed. Third, the reconstruction for the levels of detail (LoDs) of 1-3 (CityGML website) of 3D models was demonstrated. Fourth, different data sources for 3D model reconstruction were studied. The strengths and weaknesses of using the different data sources were addressed. Mobile laser scanning (MLS), unmanned aerial vehicle (UAV) images, airborne laser scanning (ALS), and the Finnish National Land Survey’s open geospatial data sources e.g. a topographic database, were employed as test data. Among these data sources, MLS data from three different systems were explored, and three different densities of ALS point clouds (0.8, 8 and 50 points/m2) were studied. The results were compared with reference data such as an orthophoto with a ground sample distance of 20cm or measured reference points from existing software to evaluate their quality. The results showed that 74.6% of building roofs were reconstructed with the automated process. The resulting building models provided an average height deviation of 15 cm. A total of 6% of model points had a greater than one-pixel deviation from laser points. A total of 2.5% had a deviation of greater than two pixels. The pixel size was determined by the average distance of input laser points. The 3D roads were reconstructed with an average width deviation of 22 cm and an average height deviation of 14 cm. The results demonstrated that 93.4% of building roofs were correctly classified from sparse ALS and that 93.3% of power line points are detected from the six sets of dense ALS data located in forested areas. This study demonstrates the operability of 3D model construction for LoDs of 1-3 via the proposed methodologies and datasets. The study is beneficial to future applications, such as 3D-model-based navigation applications, the updating of 2D topographic databases into 3D maps and rapid, large-area 3D scene reconstruction. 3D-teknologiat ovat tulleet yhä suositummiksi niiden sovellusalojen lisääntyessä teollisuudessa, kuluttajatuotteissa, terveydenhuollossa, koulutuksessa ja hallinnossa. Ennusteiden mukaan 3D-mallinnus- ja -kartoitusmarkkinat kasvavat vuoden 2013 1,1 miljardista dollarista 7,7 miljardiin vuoteen 2018 mennessä. Erilaisia aineistoja käyttäviä 3D-mallinnustekniikoita tarvitaankin yhä enemmän. Tässä väitöskirjatutkimuksessa kehitettiin automaattisen pistepilviaineiston luokittelutekniikoita ja rekonstruoitiin 3D-ympäristöja (maanpintamalleja, rakennuksia ja tieverkkoja). Georeferoitujen binääristen kuvien prosessointitekniikoita kehitettiin useiden pilvipisteaineistojen luokitteluun. Työssä esitetään robusteja menetelmiä alkuperäisestä pistepilvestä 3D-malliin eri CityGML-standardin tarkkuustasoilla. Myös eri aineistolähteitä 3D-mallien rekonstruointiin tutkittiin. Eri aineistolähteiden käytön heikkoudet ja vahvuudet analysoitiin. Testiaineistona käytettiin liikkuvalla keilauksella (mobile laser scanning, MLS) ja ilmakeilauksella (airborne laser scanning, ALS) saatua laserkeilausaineistoja, miehittämättömillä lennokeilla (unmanned aerial vehicle, UAV) otettuja kuvia sekä Maanmittauslaitoksen avoimia aineistoja, kuten maastotietokantaa. Liikkuvalla laserkeilauksella kerätyn aineiston osalta tutkimuksessa käytettiin kolmella eri järjestelmällä saatua dataa, ja kolmen eri tarkkuustason (0,8, 8 ja 50 pistettä/m2) ilmalaserkeilausaineistoa. Tutkimuksessa saatuja tulosten laatua arvioitiin vertaamalla niitä referenssiaineistoon, jona käytettiin ortokuvia (GSD 20cm) ja nykyisissä ohjelmistoissa olevia mitattuja referenssipisteitä. 74,6 % rakennusten katoista saatiin rekonstruoitua automaattisella prosessilla. Rakennusmallien korkeuksien keskipoikkeama oli 15 cm. 6 %:lla mallin pisteistä oli yli yhden pikselin poikkeama laseraineiston pisteisiin verrattuna. 2,5 %:lla oli yli kahden pikselin poikkeama. Pikselikoko määriteltiin kahden laserpisteen välimatkan keskiarvona. Rekonstruoitujen teiden leveyden keskipoikkeama oli 22 cm ja korkeuden keskipoikkeama oli 14 cm. Tulokset osoittavat että 93,4 % rakennuksista saatiin luokiteltua oikein harvasta ilmalaserkeilausaineistosta ja 93,3 % sähköjohdoista saatiin havaittua kuudesta tiheästä metsäalueen ilmalaserkeilausaineistosta. Tutkimus demonstroi 3D-mallin konstruktion toimivuutta tarkkuustasoilla (LoD) 1-3 esitetyillä menetelmillä ja aineistoilla. Tulokset ovat hyödyllisiä kehitettäessä tulevaisuuden sovelluksia, kuten 3D-malleihin perustuvia navigointisovelluksia, topografisten 2D-karttojen ajantasaistamista 3D-kartoiksi, ja nopeaa suurten alueiden 3D-ympäristöjen rekonstruktiota

Automated Extraction of 3D Building Windows from Mobile LiDAR Data

The three-dimensional (3D) city models have gained more and more attentions because of their considerable potential applications at present. In particular, the demands for Level of Detail (LoD) building models become urgent. Mobile Laser Scanning (MLS) has supplied a brand-new technology in the acquisition and update of 3D information in urban off-terrain features, particularly for building façade details. Accordingly, generating LoD3 building models from MLS point clouds becomes a new trend in recent studies. As a consequence, a method that can accurately and automatically extract 3D windows from raw MLS point clouds is presented in this thesis. To provide solid and credible information for LoD3 building models, this automated method endeavors to identify window frames on building facades from MLS point clouds. This algorithm can typically be regarded as a stepwise procedure to interpret MLS point clouds as semantic features. A voxel-based upward-growing method is firstly applied to distinguish non-ground points from ground points. Noise is then filtered out from non-ground points by statistical analysis. In order to segment out the building facades, all the remaining non-ground points are clustered based on conditional Euclidean clustering algorithm; clusters whose density and width are over a given threshold will be designated as points for building facades. After a building façade is successfully extracted, a volumetric box is created to contain façade points so that neighbours of each point can be operated. A manipulator is finally applied according to the structural characteristics of window frames to extract the potential window points. The experimental results demonstrate that the proposed algorithm can successfully extract the rectangular or curved windows in the test datasets with promising accuracies. The 2D validation and 3D validation were both conducted in this study. In the 2D validation, the lowest F-measure of the test datasets is 0.740, and the highest can be 0.977. While in the 3D validation, the lowest correctness of the test dataset is 79.58%, and the highest can be 97.96%. After further analysis of the experimental results, it was found that, for those windows concave on walls or with curtains drawn, the performance of the proposed method was influenced. Furthermore, big holes caused by system errors in raw point clouds also had negative impacts on the proposed method. In conclusion, this thesis makes a considerable contribution to extracting 3D rectangular, irregular and arc-rounded windows from noisy MLS point clouds with high accuracy and high efficiency. It has supplied a promising method for generating LoD3 building models

Extraction of Vertical Walls from Mobile Laser Scanning Data for Solar Potential Assessment

In recent years there has been an increasing demand among home owners for cost effective sustainable energy production such as solar energy to provide heating and electricity. A lot of research has focused on the assessment of the incoming solar radiation on roof planes acquired by, e.g., Airborne Laser Scanning (ALS). However, solar panels can also be mounted on building facades in order to increase renewable energy supply. Due to limited reflections of points from vertical walls, ALS data is not suitable to perform solar potential assessment of vertical building facades. This paper focuses on a new method for automatic solar radiation modeling of facades acquired by Mobile Laser Scanning (MLS) and uses the full 3D information of the point cloud for both the extraction of vertical walls covered by the survey and solar potential analysis. Furthermore, a new method isintroduced determining the interior and exterior face, respectively, of each detected wall in order to calculate its slope and aspect angles that are of crucial importance for solar potential assessment. Shadowing effects of nearby objects are considered by computing the 3D horizon of each point of a facade segment within the 3D point cloud

Update urban basemap by using the LiDAR mobile mapping system : the case of Abu Dhabi municipal system

Basemaps are the main resource used in urban planning and in building and infrastructure asset management. These maps are used by citizens and by private and public stakeholders. Therefore, accurate, up-to-date geoinformation of reference are needed to provide a good service. In general, basemaps have been updated by aerial photogrammetry or field surveying, but these methods are not always possible and alternatives need to be sought. Current limitations and challenges that face traditional field surveys include areas with extreme weather, deserts or artic environments, and flight restrictions due to proximity with other countries if there is not an agreement. In such cases, alternatives for large-scale are required. This thesis proposes the use of a mobile mapping system (MMS) to update urban basemaps. Most urban features can be extracted from point cloud using commercial software or open libraries. However, there are some exceptions: manhole covers, or hidden elements even with captures from defferent perspective, the most common building corners. Therefore, the main objective of this study was to establish a methodology for extracting manholes automatically and for completing hidden corners of buildings, so that urban basemaps can be updated. The algorithm developed to extract manholes is based on time, intensity and shape detection parameters, whereas additional information from satellite images is used to complete buildings. Each municipality knows the materials and dimensions of its manholes. Taking advantage of this knowledge, the point cloud is filtered to classify points according to the set of intensity values associated with the manhole material. From the classified points, the minimum bounding rectangles (MBR) are obtained and finally the shape is adjusted and drawn. We use satellite imagery to automatically digitize the layout of building footprints with automated software tools. Then, the visible corners of buildings from the LiDAR point cloud are imported and a fitting process is performed by comparing them with the corners of the building from the satellite image. Two methods are evaluated to establish which is the most suitable for adjustment in these conditions. In the first method, the differences in X and Y directions are measured in the corners, where LiDAR and satellite data are available, and is often computed as the average of the offsets. In the second method, a Helmert 2D transformation is applied. MMS involves Global Navigation Satellite Systems (GNSS) and Inertial Measurement Units (IMU) to georeference point clouds. Their accuracy depends on the acquisition environment. In this study, the influence of the urban pattern is analysed in three zones with varied urban characteristics: different height buildings, open areas, and areas with a low and high level of urbanization. To evaluate the efficiency of the proposed algorithms, three areas were chosen with varying urban patterns in Abu Dhabi. In these areas, 3D urban elements (light poles, street signs, etc) were automatically extracted using commercial software. The proposed algorithms were applied to the manholes and buildings. The completeness and correctness ratio, and geometric accuracy were calculated for all urban elements in the three areas. The best success rates (>70%) were for light poles, street signs and road curbs, regardless of the height of the buildings. The worst rate was obtained for the same features in peri-urban areas, due to high vegetation. In contrast, the best results for trees were found in theses areas. Our methodology demonstrates the great potential and efficiency of mobile LiDAR technology in updating basemaps; a process that is required to achieve standard accuracy in large scale maps. The cost of the entire process and the time required for the proposed methodology was calculated and compared with the traditional method. It was found that mobile LiDAR could be a standard cost-efficient procedure for updating maps.La cartografía de referencia es la principal herramienta en planificación urbanística, y gestión de infraestructuras y edificios, al servicio de ciudadanos, empresas y administración. Por esta razón, debe estar actualizada y ser lo más precisa posible. Tradicionalmente, la cartografía se actualiza mediante fotogrametría aérea o levantamientos terrestres. No obstante, deben buscarse alternativas válidas para escalas grandes, porque no siempre es posible emplear estas técnicas debido a las limitaciones y retos actuales a los que se enfrenta la medición tradicional en algunas zonas del planeta, con meteorología extrema o restricciones de vuelo por la proximidad a la frontera con otros países. Esta tesis propone el uso del sistema Mobile Mapping System (MMS) para actualizar la cartografía urbana de referencia. La mayoría de los elementos pueden extraerse empleando software comercial o librerías abiertas, excepto los registros de servicios. Los elementos ocultos son otro de los inconvenientes encontrados en el proceso de creación o actualización de la cartografía, incluso si se dispone de capturas desde diferentes puntos de vista. El caso más común es el de las esquinas de edificios. Por ello, el principal objetivo de este estudio es establecer una metodología de extracción automática de los registros y completar las esquinas ocultas de los edificios para actualizar cartografía urbana. El algoritmo desarrollado para la detección y extracción de registros se basa en parámetros como el tiempo, la intensidad de la señal laser y la forma de los registros, mientras que para completar los edificios se emplea información adicional de imágenes satélite. Aprovechando el conocimiento del material y dimensión de los registros, en disposición de los gestores municipales, el algoritmo propuesto filtra y clasifica los puntos de acuerdo a los valores de intensidad. De aquellos clasificados como registros se calcula el mínimo rectángulo que los contiene (Minimum Bounding Rectangle) y finalmente se ajusta la forma y se dibuja. Las imágenes de satélite son empleadas para obtener automáticamente la huella de los edificios. Posteriormente, se importan las esquinas visibles de los edificios obtenidas desde la nube de puntos y se realiza el ajuste comparándolas con las obtenidas desde satélite. Para llevar a cabo este ajuste se han evaluado dos métodos, el primero de ellos considera las diferencias entre las coordenadas XY, desplazándose el promedio. En el segundo, se aplica una transformación Helmert2D. MMS emplea sistemas de navegación global por satélite (Global Navigation Satellite Systems, GNSS) e inerciales (Inertial Measurement Unit, IMU) para georreferenciar la nube de puntos. La precisión de estos sistemas de posicionamiento depende del entorno de adquisición. Por ello, en este estudio se han seleccionado tres áreas con distintas características urbanas (altura de edificios, nivel de urbanización y áreas abiertas) de Abu Dhabi con el fin de analizar su influencia, tanto en la captura, como en la extracción de los elementos. En el caso de farolas, señales viales, árboles y aceras se ha realizado con software comercial, y para registros y edificios con los algoritmos propuestos. Las ratios de corrección y completitud, y la precisión geométrica se han calculado en las diferentes áreas urbanas. Los mejores resultados se han conseguido para las farolas, señales y bordillos, independientemente de la altura de los edificios. La peor ratio se obtuvo para los mismos elementos en áreas peri-urbanas, debido a la vegetación. Resultados opuestos se han conseguido en la detección de árboles. El coste económico y en tiempo de la metodología propuesta resulta inferior al de métodos tradicionales. Lo cual demuestra el gran potencial y eficiencia de la tecnología LiDAR móvil para la actualización cartografía de referenciaPostprint (published version

Photovoltaic potential in building façades

Tese de doutoramento, Sistemas Sustentáveis de Energia, Universidade de Lisboa, Faculdade de Ciências, 2018Consistent reductions in the costs of photovoltaic (PV) systems have prompted interest in applications with less-than-optimum inclinations and orientations. That is the case of building façades, with plenty of free area for the deployment of solar systems. Lower sun heights benefit vertical façades, whereas rooftops are favoured when the sun is near the zenith, therefore the PV potential in urban environments can increase twofold when the contribution from building façades is added to that of the rooftops. This complementarity between façades and rooftops is helpful for a better match between electricity demand and supply. This thesis focuses on: i) the modelling of façade PV potential; ii) the optimization of façade PV yields; and iii) underlining the overall role that building façades will play in future solar cities. Digital surface and solar radiation modelling methodologies were reviewed. Special focus is given to the 3D LiDAR-based model SOL and the CAD/plugin models DIVA and LadyBug. Model SOL was validated against measurements from the BIPV system in the façade of the Solar XXI building (Lisbon), and used to evaluate façade PV potential in different urban sites in Lisbon and Geneva. The plugins DIVA and LadyBug helped assessing the potential for PV glare from façade integrated photovoltaics in distinct urban blocks. Technologies for PV integration in façades were also reviewed. Alternative façade designs, including louvers, geometric forms and balconies, were explored and optimized for the maximization of annual solar irradiation using DIVA. Partial shading impacts on rooftops and façades were addressed through SOL simulations and the interconnections between PV modules were optimized using a custom Multi-Objective Genetic Algorithm. The contribution of PV façades to the solar potential of two dissimilar neighbourhoods in Lisbon was quantified using SOL, considering local electricity consumption. Cost-efficient rooftop/façade PV mixes are proposed based on combined payback times. Impacts of larger scale PV deployment on the spare capacity of power distribution transformers were studied through LadyBug and SolarAnalyst simulations. A new empirical solar factor was proposed to account for PV potential in future upgrade interventions. The combined effect of aggregating building demand, photovoltaic generation and storage on the self-consumption of PV and net load variance was analysed using irradiation results from DIVA, metered distribution transformer loads and custom optimization algorithms. SOL is shown to be an accurate LiDAR-based model (nMBE ranging from around 7% to 51%, nMAE from 20% to 58% and nRMSE from 29% to 81%), being the isotropic diffuse radiation algorithm its current main limitation. In addition, building surface material properties should be regarded when handling façades, for both irradiance simulation and PV glare evaluation. The latter appears to be negligible in comparison to glare from typical glaze/mirror skins used in high-rises. Irradiation levels in the more sunlit façades reach about 50-60% of the rooftop levels. Latitude biases the potential towards the vertical surfaces, which can be enhanced when the proportion of diffuse radiation is high. Façade PV potential can be increased in about 30% if horizontal folded louvers becomes a more common design and in another 6 to 24% if the interconnection of PV modules are optimized. In 2030, a mix of PV systems featuring around 40% façade and 60% rooftop occupation is shown to comprehend a combined financial payback time of 10 years, if conventional module efficiencies reach 20%. This will trigger large-scale PV deployment that might overwhelm current grid assets and lead to electricity grid instability. This challenge can be resolved if the placement of PV modules is optimized to increase self-sufficiency while keeping low net load variance. Aggregated storage within solar communities might help resolving the conflicting interests between prosumers and grid, although the former can achieve self-sufficiency levels above 50% with storage capacities as small as 0.25kWh/kWpv. Business models ought to adapt in order to create conditions for both parts to share the added value of peak power reduction due to optimized solar façades.Fundação para a Ciência e a Tecnologia (FCT), SFRH/BD/52363/201

Mobile Laser Scanning – System development, performance and applications

Osajulkaisut: Publication 1: Antero Kukko, Sanna Kaasalainen, and Paula Litkey. 2008. Effect of incidence angle on laser scanner intensity and surface data. Applied Optics, volume 47, number 7, pages 986-992. doi:10.1364/AO.47.000986 Publication 2: Antero Kukko and Juha Hyyppä. 2009. Small-footprint laser scanning simulator for system validation, error assessment, and algorithm development. Photogrammetric Engineering and Remote Sensing, volume 75, number 9, pages 1177-1189. Publication 3: Antero Kukko, Constantin-Octavian Andrei, Veli-Matti Salminen, Harri Kaartinen, Yuwei Chen, Petri Rönnholm, Hannu Hyyppä, Juha Hyyppä, Ruizhi Chen, Henrik Haggrén, Iisakki Kosonen, and Karel Čapek. 2007. Road environment mapping system of the Finnish Geodetic Institute - FGI ROAMER -. In: Petri Rönnholm, Hannu Hyyppä, and Juha Hyyppä (editors). Proceedings of the ISPRS Workshop on Laser Scanning 2007 and SilviLaser 2007. Espoo, Finland. 12-14 September 2007. International Society for Photogrammetry and Remote Sensing. International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences, volume 36, part 3 / W52, pages 241-247. ISSN 1682-1777. Publication 4: Antero Kukko, Harri Kaartinen, Juha Hyyppä, and Yuwei Chen. 2012. Multiplatform mobile laser scanning: Usability and performance. Sensors, volume 12, number 9, pages 11712-11733. doi:10.3390/s120911712 Publication 5: Harri Kaartinen, Juha Hyyppä, Antero Kukko, Anttoni Jaakkola, and Hannu Hyyppä. 2012. Benchmarking the performance of mobile laser scanning systems using a permanent test field. Sensors, volume 12, number 9, pages 12814-12835. doi:10.3390/s120912814 Publication 6: P. Alho, A. Kukko, H. Hyyppä, H. Kaartinen, J. Hyyppä, and A. Jaakkola. 2009. Application of boat-based laser scanning for river survey. Earth Surface Processes and Landforms, volume 34, number 13, pages 1831-1838. doi:10.1002/esp.1879 Publication 7: Matti Vaaja, Juha Hyyppä, Antero Kukko, Harri Kaartinen, Hannu Hyyppä, and Petteri Alho. 2011. Mapping topography changes and elevation accuracies using a mobile laser scanner. Remote Sensing, volume 3, number 3, pages 587-600. doi:10.3390/rs3030587Laser scanning is a surveying technique used for mapping topography, vegetation, urban areas and infrastructure, ice, and other targets of interest. Its application on a terrestrial mobile platform is a promising method for effectively collecting three-dimensional data for complex environments and for producing model information for location-based services necessitating rapidly collected and up-to-date data. Development of mobile laser scanning (MLS) systems for such purposes is presented in this study. Different aspects of this technology were analyzed in laboratory experiments, simulations and field tests, in order to understand their effects on the ranging, intensity and point cloud data, especially in terms of point distribution and accuracy. In order to validate the performance of the developed ROAMER and AKHKA MLS systems, various three-dimensional mapping tasks were performed during an international benchmarking test, as well as in the field in numerous projects. The results showed that the proposed systems can reliably provide accurate data. It has also been shown that the various modalities of the systems allow data acquisition in numerous application scenarios and environments not previously possible. MLS improves the data output compared to terrestrial laser scanning (TLS) and outperforms airborne laser scanning (ALS) in ranging precision and point density. As a result, MLS is well suited to fill the gap between these two previously dominant 3D data acquisition techniques.Laserkeilaus on mittaustekniikka, jota käytetään maaston topografian kasvillisuuden, rakennettujen alueiden, infrastruktuurin, jään ja muiden kohteiden kartoitukseen. Tekniikan soveltaminen liikkuvalle alustalle on lupaava menetelmä monimuotoisten ympäristöjen tehokkaaseen kolmiulotteiseen mittaamiseen ja mallinnustiedon tuottamiseen paikkatietopalveluihin, jotka edellyttävät tiedon nopeaa hankintaa ja ajantasaisuutta. Tässä tutkimuksessa kehitettiin liikkuvia laserkeilausjärjestelmiä (MLS). Eri tekijöiden vaikutuksia etäisyys- ja intensiteettihavaintoihin, pistejakaumaan ja tarkkuuteen selvitettiin laboratoriokokein, simuloimalla ja koetöin. Tutkimuksessa kehitettyjen ROAMER ja AKHKA MLS-järjestelmien suorituskykyä kolmiulotteisen mittaustiedon tuottamiseen erilaisissa kartoitustehtävissä tutkittiin kansainvälisessä vertailututkimuksessa kaupunkitestikentän avulla, mutta lisäksi käytännön sovelluksissa useassa eri projektissa. Tutkimuksen tulokset osoittavat, että kehitetyt MLS järjestelmät tuottavat tarkkaa tietoa luotettavasti. Järjestelmien monikäyttöisyys mahdollistaa aineistonhankinnan eri sovellustapauksissa ja ympäristöissä tavalla, joka ei ole aikaisemmin ollut mahdollista. Liikkuva laserkeilaus parantaa merkittävästi mittauksen tehokkuutta maalaserkeilaukseen verrattuna, ja ylittää lentolaserkeilauksen suorituskyvyn etäisyysmittauksen tarkkuudessa ja pistetiheydessä. Liikkuva laserkeilaus tarjoaakin näitä kahta aikaisemmin vallitsevaa 3D-mittausteknologiaa hyvin täydentävän kartoitusmenetelmän

Charakterisierung von Trennflächengefügen mittels automatisierter Flächenerfassung an TLS gestützten 3D-Aufschlussmodellen

Für viele Tiefengeothermie- und manche Kohlenwasserstofflagerstätten sind natürliche Bruchnetzwerke von sehr großer Bedeutung, da wirtschaftlich nutzbare Fließraten und Porositäten von ihnen abhängen. Aufschlussanalogstudien sind ein wichtiges und ver-gleichsweise kosteneffektives Werkzeug, um Vorhersagen über potenzielle geklüftete Reservoire im Untergrund zu treffen. Auch zur Beurteilung der geomechanischen Eigenschaften von Gesteinskörpern müssen Bruchnetzwerke anhand von Aufschlüssen charakterisiert werden. Im Rahmen von Aufschlussanalogstudien kommen vermehrt Fernerkundungstechniken wie TLS (Terrestrisches Laserscanning) zum Einsatz. Damit gewonnene 3D-Punktwolken sind die Grundlage für hochauflösende digitale Aufschluss-modelle („Digital Outcrop Models“, kurz DOMs). Mit DOMs lassen sich (i) Orientie-rungen, Positionen und Geometrien von Trennflächen extrahieren, (ii) Felddaten präzise räumlich integrieren, (iii) verschiedene Abbaustände in Steinbrüchen erfassen und vergleichen, (iv) sedimentärer Strukturen räumlich interpretieren sowie (v) strukturelle Rahmen für Reservoirmodelle gewinnen. Im Rahmen der vorliegenden Dissertation wurden fotorealistische DOMs von Stein-brüchen im Buntsandstein (Oberes Perm bis Untere Trias), im Muschelkalk (Mittlere Trias) und einem natürlichen Granitaufschluss (Karbon) als Analoga potenzieller geo-thermischer Reservoire im Untergrund des Oberrheingrabens (SW-Deutschland, E-Frankreich) erstellt. Der Hauptteil der Arbeit widmet sich der Entwicklung von Techni-ken zur automatisierten Extraktion von Flächeninformationen aus DOMs, insbesondere von Kluftinformationen, die sich zur Modellierung von diskreten Bruchnetzwerken verwenden lassen. In Kooperation mit der Abteilung Geoinformatik des Geographischen Instituts, Universi-tät Heidelberg, wurde ein robuster Algorithmus zur automatisierten Berechnung von Flächeninformationen in 3D-Punktwolken entwickelt. Die daraus hervorgegangene automatisierte Flächenanalyse wird in der vorliegenden Dissertation vorgestellt. Sie basiert auf Segmentierung mittels Bereichswachstumsverfahren und lässt sich über eine Reihe von Homogenitätskriterien aktiv an unterschiedliche Oberflächen, Datenqualitäten und Fragestellungen adaptieren. Die Möglichkeiten dieser sehr flexiblen Methode werden ausführlich beleuchtet und die Plausibilität automatisiert erstellter Flächensegmente überprüft. Der bearbeitete Granitaufschluss besitzt komplexe Flächenformen, die genutzt wurden, um die Flächenerfassung mit der automatisierten Flächenanalyse anhand verschiedener statistischer Verfahren zu validieren. Zu diesem Zweck wurden auch mehr als 1000 Flächen konventionellen mit einem Gefügekompass aufgenommen und die Orientierungen von 122 Flächen mit einer händischen digitalen Referenzmethode im DOM eingemessen. Die Segmentgröße ist eines der wichtigsten Kriterien der automatisierten Flächenanalyse zum Verwerfen irrelevanter Segmente. Sie ist durch die Anzahl der Punkte eines Seg-ments definiert. Die Punktmenge pro Flächeneinheit ist in TLS-Punktwolken jedoch abhängig von der Perspektive des Scanners zur gemessenen Oberfläche. Es wurde ein trigonometrisches Verfahren zur Korrektur dieses perspektivischen Einflusses hergeleitet und in den Algorithmus der automatisierten Flächenanalyse integriert. Damit berechnete Punktanzahlen sind proportional zum Flächeninhalt des Segments, der daraus auto-matisiert berechnet werden kann. Diese Segmentgrößenkorrektur wurde durch Messun-gen an einer künstlichen Standardfläche und in zwei DOMs mittels an den Punktwolken angelegte 2D-Polygonen detailliert validiert. Für einen Aufschlusses im Buntsandstein wurde exemplarisch ein diskretes Bruchnetz-werk modelliert, das auf digital extrahierten Kluftparametern basiert. Der präsentierte Workflow bietet neue Einsichten in detaillierte virtuelle Messungen von Kluftintensitäten (P10-Kennzahl) und zeigt Möglichkeiten und Grenzen digitaler Charakterisierung von Bruchnetzwerken auf. Die Validierung der digitalen Orientierungsmessungen am Granitaufschluss ergab eine durchschnittliche Abweichung zu den Kompassmessungen von 5,0° für Vergleiche an einzelnen Flächen und Abweichungen zwischen 1,0° und 1,6° für die mittlere Orientierung von drei erkannten Kluftscharen. Der Vergleich mit einer digitalen Refe-renzmethode und weitere Qualitätskontrollen weisen deutlich darauf hin, dass die mit der automatisierten Flächenanalyse gemessenen Orientierungen eine signifikant höhere Ge-nauigkeit als die Werte der Kompassmessungen haben. Die Überprüfung der Segmentgrößenkorrektur mit der künstlichen Standardfläche ergab für Sichtwinkel unter 80° eine systematische Abweichung der berechneten Flächeninhalte von +3 %. Die zufällige Abweichung ist geringer: die Messwerte liegen im Bereich ±1 % um ihren Mittelwert, der Variationskoeffizient beträgt 0,45 %. Die systematische Abwei-chung konnte durch die Eigenschaften des verwendeten TLS erklärt und mit zwei entwickelten Verfahren fast vollständig korrigiert werden. Die Abweichungen zu Flächeninhalten von automatisiert an die segmentierten Punktwolken zweier DOMs angelegter 2D-Polygone haben einen Median von 6,4 % sowie 4,3 % für Sichtwinkel unter 70° und 4,9 % und 3,9 % für Sichtwinkel unter 60°. Allerdings hängt die Überein-stimmung der Ergebnisse aus den Methoden stark von der gewählten maximalen Kantenlänge des Polygonzugs ab. Einzelne Trennflächen oder gesamte Bruchnetzwerke können mit den in dieser Disser-tation präsentierten TLS-basierten Methoden risikoarm, automatisiert und dadurch effi-zient charakterisiert werden. Unzugängliche Aufschlussareale werden dadurch messtech-nisch erschlossen. Etablierte händische Messtechniken lassen sich virtuell in DOMs adaptieren. Ermittelte Positionen, Orientierungen und Geometrien von Flächen und anderer Strukturen sind von sehr hoher Genauigkeit und eignen sich als Datenbasis für Kluftmodellierungen, die Abschätzungen der hydraulischen und geomechanischen Eigenschaften von Kluftnetzwerken ermöglichen