Christoph Holst

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Verified

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• Prof. Dr.-Ing.
• Professor (Full) at Technical University of Munich

Despite recent advancements in surface reconstruction, Level of Detail (LoD) 3 building reconstruction remains an unresolved challenge. The main issue pertains to the object-oriented modelling paradigm, which requires georeferencing, watertight geometry, facade semantics, and low-poly representation -- Contrasting unstructured mesh-oriented models....

The fast improvement of laser scanning technology has pushed terrestrial laser scanning (TLS) to the forefront of geodetic deformation analysis. As TLS becomes more integrated into this field, it is critical to construct a stochastic model that appropriately describes the uncertainty in TLS measurements. This includes creating a valid and fully pop...

Permanent laser scanning technology has been utilized for continuous monitoring of natural hazards over the past decade, owing to its ability to capture high spatio-temporal resolution point cloud time series, termed 4D point clouds (3D space + time). These 4D point clouds from PLS enable the detection of intricate surface changes and deeper insigh...

Analyzing objects concerning their static and dynamic change is mostly performed with IMU (Inertial Mea- surement Units) or GNSS (Global Navigation Satellite System) sensors fixed to a physically defined surface. We can use a total station to record additional data or support other sensors by referencing them to a homoge- neous coordinate frame. Li...

Radio telescopes are pivotal in receiving radio frequencies from space. These telescopes, typically featuring parabolic dishes, focus radio waves onto a central receiving point to amplify the incoming signal. The stability of the telescope's main reflector's shape across various orientations is crucial, as deformations can distort the received sign...

Das Forschungsprojekt AImon5.0 fokussiert sich auf die Echtzeitüberwachung gravitativer Massenbewegungen am Trierer Augenscheiner, einer geologisch komplexen Felsformation mit hoher Instabilität. Im Rahmen des Projekts wurde ein permanentes Monitoring-System auf Basis eines Laserscanners installiert, der kontinuierlich 4D-Daten zur Erfassung von Fe...

Facade semantic segmentation is a long-standing challenge in photogrammetry and computer vision. Although the last decades have witnessed the influx of facade segmentation methods, there is a lack of comprehensive facade classes and data covering the architectural variability. In ZAHA, we introduce Level of Facade Generalization (LoFG), novel hiera...

Structured semantic 3D city models are pivotal in creating urban 3D digital twins. The wide adoption of such models has been primarily enabled by robust, model-based, and automatic 3D reconstruction methods. However, these methods impose requirements on the reconstruction, mainly restricting the solution space to several model types and relying on...

In this paper we propose a monitoring method that allows the inclusion of point clouds into a geodetic monitoring network. Consequently, network adjustment and a rigorous deformation analysis can be performed allowing consistent error propagation and trustful significance calculation. We introduce a supervised pipeline based on ICP-matching of smal...

Thermal point clouds integrate thermal radiation and laser point clouds effectively. However, the semantic information for the interpretation of building thermal point clouds can hardly be precisely inferred. Transferring the semantics encapsulated in 3D building models at LoD3 has a potential to fill this gap. In this work, we propose a workflow e...

Numerous navigation applications rely on data from global navigation satellite systems (GNSS), even though their accuracy is compromised in urban areas, posing a significant challenge, particularly for precise autonomous car localization. Extensive research has focused on enhancing localization accuracy by integrating various sensor types to addres...

Numerous navigation applications rely on data from global navigation satellite systems (GNSS), even though their accuracy is compromised in urban areas, posing a significant challenge, particularly for precise autonomous car localization. Extensive research has focused on enhancing localization accuracy by integrating various sensor types to addres...

The permanent terrestrial laser scanning (PLS) system has opened the possibilities for efficient data acquisition with high-temporal and spatial resolution, thus allowing for improved capture and analyses of complex geomorphological changes on the Earth's surface. Accurate georeferencing of generated four-dimensional point clouds (4DPC) from PLS is...

Point cloud data acquired via laser scanning or stereo matching of photogrammetry imagery has become an emerging and vital data source in an increasing research and application field. However, point cloud processing can be highly challenging due to an ever-increasing amount of points and the demand for handling the data in near real-time. In this p...

Analyzing objects concerning their periodic behavior is mostly performed with IMU (Inertial Measurement Units) or GNSS (Global Navigation Satellite System) sensors fixed to its surface. For connecting observations, sensors have to be assigned to the same reference frame in space and time as a pre-requisite. Using LiDAR (Light Detection and Ranging)...

Landslides represent a significant natural hazard with wide-reaching impacts. Addressing the challenge of accurately detecting and monitoring landslides, this research introduces a novel approach that combines feature tracking with histogram analysis for efficient outlier removal. Distinct from existing methods, our approach leverages advanced hist...

The rising global energy demand has made it essential to reduce energy consumption in the residential building stock. Adding a new insulating envelope with Renewable Energy Sources (RESs) onto the existing buildings’ facade is one way to achieve zero energy consumption in residential buildings. The ENSNARE project aims to semi-automate this process...

Laser scanning is a wide-spread practice to capture the environment. Besides the fields of robotics and self-driving cars, it has been applied in the field of engineering geodesy for documentation and monitoring purposes for many years. The registration of scans is still one of the main sources of uncertainty in the final point cloud. This paper pr...

In diesem Beitrag werden zwei Ansätze für die hochgenaue Überwachung von Felsstürzen mittels terrestrischem Laserscanning vorgestellt. Beide Verfahren erzeugen aus den Punktwolken Einzelpunkte, die in allen Epochen eindeutig wiedergefunden werden können. Im ersten Verfahren geschieht dies auf Basis von Punktwolken-Patches, für die die Bewegung zwis...

Analyzing the uncertainty of terrestrial laser scanners (TLS) requires the separation of the erroneously biased part of a point cloud. Therefore, the exact geometry of the scanned object must be known. While this can be realized for smaller objects (up to a few meters) by using a known geometric shape or by scanning the surface with a sensor of sup...

Performing deformation analyses with high accuracy demands using terrestrial laser scanners is very challenging due to insufficient knowledge about the error budget and correlations. Terrestrial laser scans suffer from random and systematic errors that degrade the quality of the point cloud. Even though the vast majority of systematic errors can be...

In diesem Beitrag wird ein innovatives GNSS-basiertes Monitoringsystem vorgestellt und dessen erreichbare Genauigkeit anhand verschiedener Messreihen evaluiert. Das Permanentsystem „Happy Monitoring“ der gleichnamigen Schweizer Firma basiert auf der kontinuierlichen Messung von RTK-Koordinaten, die mittels eines adaptiven Glättungsalgorithmus in Ec...

Terrestrial laser scanners (TLSs) offer a possibility for more automated and efficient deformation monitoring of civil engineering structures with higher spatial resolution than standard methods, as well as without the necessity of permanently installing the monitoring equipment. In such applications, scanners are usually placed so that the lines o...

Performing deformation analyses with high accuracy demands using terrestrial laser scanners is very challenging due to insufficient knowledge about the error budget and correlations. Terrestrial laser scans suffer from random and systematic errors that mitigate the quality of the point cloud. Even though the vast majority of systematic errors can b...

Water dams are an important infrastructure component for energy generation, water supply and flood control. Regular inspections of the structures for damage and deformation are necessary for safe operation and to ensure stability. In addition to the traditional concepts of geodetic network measurement, laser scan data can be used to deliver areal i...

The classic pipeline of 3D point cloud registration involves two steps: point feature matching and the globally consistent refinement. We focus on the first step, which can be further divided into three parts: keypoint detection, feature descriptor extraction and pairwise-point correspondence estimation. In practical applications, point feature mat...

We present a method to include virtual target points from laser scanning into the point-based rigorous deformation analysis to derive precise 3D deformation vectors. This method overcomes the challenge of missing point identities in laser scans and is developed especially for geo-monitoring applications that demand an early identification of deform...

Quasars are nowadays the basis to determine the world's absolute orientation in space by radio interferometry (VLBI). The global network of baselines measured by the used radio telescopes, which vary greatly in size, is subject to various influences that have an impact on the International Terrestrial Reference Frame. Among others, those influences...

In geodesy and metrology several coordinate representations are known. The most important representations are polar coordinates and Cartesian coordinates. The coordinate representations are rigorously convertible into each other. Such functional relations are well-known as the direct (first) and the inverse (second) geodetic problem. Instruments li...

In almost all projects, in which terrestrial laser scanning is used, the scans must be registered after the data acquisition. Despite more and more new and automated methods for registration, the classical target-based registration is still one of the standard procedures. The advantages are obvious: independence from the scan object, the geometric...

The determination of a fully populated variance-covariance matrix (VCM) of a point cloud acquired with a terrestrial laser scanner (TLS) is not straightforward as physical correlations between TLS observations are not sufficiently known. Ignoring correlations leads to biased estimates, wrong modeling of surfaces, or the misinterpretation of geometr...

Vibration monitoring is a frequent task within the general topic of Structural Health Monitoring. For this monitoring, usually accelerometers, strain gauges, fibre optic sensors or Global Navigation Satellite System (GNSS) receivers are placed on pre-selected positions on the structure and the point-wise measurements are individually processed to e...

The perfect knowledge about the scanned object’s geometry is essential for the empirical analysis of the stochastic properties of terrestrial laser scanners (TLSs). The Bonn reference wall is intended to be used as a reference for TLS quality investigations. Therefore, it is necessary to know the geometry of the wall at each time of scanning to avo...

This article investigates the usage of terrestrial laser scanner (TLS) point clouds for monitoring the gradual movements of soil masses due to freeze-thaw activity and water saturation, commonly referred to as solifluction. Solifluction is a geomorphic process which is characteristic for hillslopes in (high-)mountain areas, primarily alpine perigla...

To assure accurate terrestrial laser scanner (TLS) point clouds, the instruments should be repeatedly calibrated in the manufacturer’s facilities, either in regular time intervals or if they fail the examination on a test-field. This workflow has drawbacks for the end-users: there is no deeper understanding of the calibration procedure and it is ti...

The point-to-point distance, the spot size and its shape limit the minimum size of objects that can be spatially resolved in a TLS point cloud. As the laser beam has a footprint of at least a few millimeters, adjacent laser spots overlap if the sampling interval is chosen small. Thus, they do not provide individual information about the object surf...

Due to improved technology terrestrial laser scanners (TLS) are increasingly used for tasks demanding high accuracy, such as deformation monitoring. Within this field, often long-term measurements are acquired, for which the temporal stability of the laser scanner’s observations need to be assured or at least its magnitude and influence factors sho...

Commonly, terrestrial laser scanners (TLSs) are calibrated on calibration fields so the scanner’s instrumental errors are estimated a priori to a given task. Such approaches presume the stability of errors with time and external influences so that the calibration parameters are valid at future measurements. Alternatively, TLSs are calibrated in-sit...

Im Bereich der GNSS-Positionierung zählen stationsspezifische Abweichungen, welche aufgrund der Antennenumgebung entstehen, zu den genauigkeitsbegrenzenden Faktoren. In diesem Beitrag wird eine Strategie zur Satellitenselektion vorgestellt, die stationsabhängige Einflüsse, wie die Signalbeugung, den Empfang von Signalen nicht direkt sichtbarer Sate...

In the area of GNSS positioning, site-dependent errors, which are caused by the antenna environment, are one of the accuracy limiting factors. In this paper a strategy for satellite selection is presented, which considers site-dependent effects like signal diffraction, Non-line-of-sight (non-line-of-sight, NLOS) reception and far-field multipath. T...

Accepted author manuscript (peer-reviewed postprint). Open access content under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/) | Published by: Springer. Springer Proceedings in Earth and Environmental Sciences. Conference proceeding: Contributions to International Conferences on...

Accepted author manuscript (peer-reviewed postprint). Open access content under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/) | Published by: Springer. Springer Proceedings in Earth and Environmental Sciences. Conference proceeding: Contributions to International Conferences on...

Due to improved technology terrestrial laser scanners (TLS) are increasingly used for tasks demanding high accuracy, such as deformation monitoring. Within this field, often long-term measurements are acquired, for which the temporal stability of the laser scanner's observations need to be assured or at least its magnitude and influence factors sho...

The point-to-point distance, the spot size and its shape limit the minimum size of objects that can be spatially resolved in a TLS point cloud. As the laser beam has a footprint of at least a few millimeters, adjacent laser spots overlap if the sampling interval is chosen small. Thus, they do not provide individual information about the object surf...

In vielen geodätischen Anwendungsbereichen, wie bspw. Überwachungsmessungen, Referenzstationsnetzwerken oder auch kinematischen Vermessungsaufgaben, werden hochgenaue Koordinaten einer statischen oder sich bewegenden GNSS-Antenne benötigt. In diesem Zusammenhang stellen stationsspezifische Abweichungen oftmals den genauigkeitsbegrenzenden Faktor da...

Zur Analyse von Bauwerksschwingungen werden in der Regel mehrere Sensoren am Bauwerk instal-liert, die jeweils hochfrequent punkthafte Messungen durchführen. Beispiele sind GNSS-Empfänger oder Beschleunigungssensoren. Aus den punkthaften Messungen wird dann auf die flächenhaften Schwingungen geschlossen, entweder nur entlang der Hauptkomponente des...

Mobile laser scanning has become an established measuring technique that is used for many applications in the fields of mapping, inventory, and monitoring. Due to the increasing operationality of such systems, quality control w.r.t. calibration and evaluation of the systems becomes more and more important and is subject to on-going research. This p...

The resolution capability of terrestrial laser scanners does not necessarily equal the scanning resolution. Laser scanners can acquire the surrounding with a point distance of less than a millimeter on ten meters but the footprint size amounts to at least a few millimeters. Hence, neighboring laser spots overlap and they are correlated as they do n...

IMPORTANT: This is just a modified (extended) version of the conference proceeding article "Improving the results of terrestrial laser scanner calibration by an optimized calibration process", in: Photogrammetrie - Laserscanning - Optische 3D-Messtechnik, Beiträge der Oldenburger 3D-Tage 2019, Hrsg: Luhmann, T., Schumacher, C., Wichmann Verlag, Ber...

Calibration of terrestrial laser scanners (TLSs) is one of the fundamental tasks for assuring the high measurement accuracy required by an increasing number of end-users. Nevertheless, the development of user-oriented calibration approaches is still an active topic of research. The calibration fields for the target-based self-calibration of TLSs de...

Deformations of the reflectors of radio telescopes used in geodetic and astrometric VLBI observations belong to the class of systematic error sources which affect the estimated position of the telescope and which necessitates correction at the observation level. The determination of the gravitationally induced deformations requires some effort and...

Zur Registrierung terrestrischer Laserscans werden seit vielen Jahren Zielzeichen eingesetzt. Aus hochaufgelösten Scans der Zielzeichen werden mit Hilfe von Algorithmen die Koordinaten der signalisierten Punkte geschätzt. Werden ebene schwarz-weiß Zielzeichen genutzt, bestimmen die Algorithmen zum einen die Ebenenorientierung der Zielzeichen und zu...

Target-based calibration is the most widely used calibration procedure for terrestrial laser scanners. Nevertheless, the current implementations of this procedure are suboptimal due to the high complexity of their calibration fields. Therefore, designing calibration fields, by selecting optimal target locations with respect to the instrument, is a...

Terrestrial laser scanner (TLS) measurements are unavoidably affected by systematic influences due to internal misalignments. The magnitude of the resulting errors can exceed the magnitude of random errors significantly deteriorating the quality of the obtained point clouds. Hence, the task of calibrating TLSs is important for applications with hig...

Terrestrial laser scanner (TLS) measurements are unavoidably affected by systematic influences due to internal misalignments. The magnitude of the resulting errors can exceed the magnitude of random errors significantly deteriorating the quality of the obtained point clouds. Hence, the task of calibrating TLSs is important for applications with hig...

Terrestrial laser scanners (TLS) suffer from internal misalignments leading to systematic measurement errors. In most cases, these systematic errors surpass the magnitude of random errors. Hence, it is necessary to account for systematic errors within the deformation analysis in order to obtain unbiased results. Within this work, we present and com...

During the registration and georeferencing of terrestrial laser scans, it is common to use targets to mark discrete points. To improve the accuracy of the registration, the uncertainties of the target center estimation (TCE) have to be minimized. The present study examines different factors influencing the precision of the TCE. Here, the focus is o...

Der terrestrische Laserscanner (TLS) ist der logische Nachfolger vom motorisierten, reflektorlos messenden Tachyme-ter. Das Messprodukt ist eine 7D-Punktwolke (X,Y,Z,I,R,G,B), die sich aufgrund ihres geometrischen und physikalischen Detailreichtums sehr gut eignet, kleine und große Objektcharakteristiken und ihre zeitliche Änderungen zu erfassen. D...

As laser scanning technology has improved a lot in recent years, terrestrial laser scanners (TLS) have become popular devices for surveying tasks with high accuracy demands, such as deformation analyses. For this reason, finding a stochastic model for TLS measurements is very important in order to get statistically reliable results. The measurement...

The target-based point cloud registration and calibration of terrestrial laser scanners (TLSs) are mathematically modeled and solved by the least-squares adjustment. However, usual stochastic models are simplified to a large amount: They generally employ a single point measurement uncertainty based on the manufacturers’ specifications. This definit...

Terrestrische Laserscanner sind in der Lage, unsere Umgebung in Form von Punktwolken dreidimensional zu erfassen. Hierbei kann geräteintern in der Regel zwischen verschiedenen räumlichen Auflösungsstufen und auch Qualitätsstufen, bezogen auf die Genauigkeit eines einzelnen Punktes, gewählt werden. In der Praxis steht jedoch meist nur eine begrenzte...

Terrestrial laser scanner (TLS) measurements suffer from systematic errors due to internal misalignments. The magnitude of the resulting errors in the point cloud exceeds the magnitude of random errors in many applications. Hence, the task of calibration is important for using laser scanners at applications with high demands regarding accuracy. How...

Terrestrial laser scanner (TLS) measurements suffer from systematic errors due to internal misalignments. The magnitude of the resulting errors in the point cloud exceeds the magni-tude of random errors in many applications. Hence, the task of calibration is important for using laser scanners at applications with high demands regarding accuracy. Ho...

Bei der Datenaufnahme mittels terrestrischem Laserscanning ist es in vielen Fällen notwendig, mehrere Scannerstandpunkte zu besetzen, um das gesamte Objekt vollständig zu vermessen. Dabei werden die Scans der einzelnen Standpunkte häufig über Zielzeichen registriert. Obwohl das Verfahren der zielzeichenbasierten Registrierung ein Standardverfahren...

In geodetic very long baseline interferometry, pairs of radio telescopes simultaneously observe signals from quasi stellar objects to estimate the baseline between their reference points. Gravity-dependent variations of the radio telescopes' reference points deteriorate the estimated baseline's accuracy since they lead to signal path variations in...

| * | AUTHOR'S COPY (open-access): http://hdl.handle.net/20.500.11811/1441 | * | The accuracy of georeferenced TLS point clouds is directly influenced by site-dependent GNSS effects, dete- riorating the accuracy of the ground control point coordi- nate estimation. Especially under challenging GNSS con- ditions, this is a crucial problem. One common...

Kinematic laser scanning with moving platforms has been used for the acquisition of 3D point clouds of our environment for many years. A main application of these mobile systems is the acquisition of the infrastructure, e.g., the road surface and buildings. Regarding this, the distance between laser scanner and object is often notably shorter than...

The ability to acquire rapid, dense and high quality 3D data has made terrestrial laser scanners (TLS) a desirable instrument for tasks demanding a high geometrical accuracy, such as geodetic deformation analyses. However, TLS measurements are influenced by systematic errors due to internal misalignments of the instrument. The resulting errors in t...

Radioteleskope werden unter anderem bei der geodätischen Very Long Baseline Interfe-rometry verwendet: Beobachten mehrere Radioteleskope dieselbe Radioquelle, lassen sich die Basislinien zwischen den jeweiligen Referenzpunkten mit einer Genauigkeit weniger Millimeter berechnen. Damit diese Genauigkeit erreicht werden kann, muss die Form- und Lagest...

Terrestrische Laserscanner sind in der Lage, unsere Umgebung in Form von Punktwolken dreidimensional zu erfassen. Dabei kann geräteintern in der Regel zwischen verschiedenen räumlichen Auflösungsstufen und auch Qualitätsstufen, bezogen auf die Genauigkeit eines einzelnen Punktes, gewählt werden. Da in der Praxis jedoch meist nur eine begrenzte Zeit...

For the sampling of natural and artificial objects with high spatial resolution, terrestrial laser scanners (TLS) or cameras, e.g., mounted on unmanned aerial vehicles (UAV), are often used. Both sensor measurements either directly lead to a point cloud or a point cloud can be derived by several photogrammetry based processing steps. If measured in...

Radio telescopes serve for astronomic observations, amongst others. To accurately process and evaluate their measurements, the geometric shape of the radio telescopes’ main reflectors should be known accurately. This shape deforms due to gravity. Therefore, these surfaces need to be inspected after manufacturing: the focal length and possible local...

For accurate astronomic and geodetic observations based on radio telescopes, the elevation-dependent deformation of the radio telescopes’ main reflectors should be known. Terrestrial laser scanning has been used for determining the corresponding changes of focal lengths and areal reflector deformations at several occasions before. New in this publi...

Measuring the 3D shape of plants for phenotyping purposes using active 3D laser scanning devices has become an important field of research. While the acquisition of stem and root structure is mostly straightforward, extensive and non-invasive measuring of the volumetric shape of leaves, i.e., the leaf thickness, is more challenging. Therefore, the...

For analyzing area-based deformations based on terrestrial laser scans, several methods exist. If there is no information about the object’s geometry, the deformations are analyzed in most cases based on point cloud differences revealed by scanning in two epochs. The point clouds are either compared directly, are previously meshed or they are filte...

Terrestrial laser scanner measurements suffer from systematic errors due to internal misalignments. The magnitude of the resulting errors in the point cloud in many cases exceeds the magnitude of random errors. Hence, the task of calibrating a laser scanner is important for applications with high accuracy demands. This paper primarily addresses the...

Portable coordinate measuring arms (CMA) represent a special class of coordinate measuring machines providing high accuracy combined with high flexibility. To obtain high accurate and reliable 3D coordinates, the kinematic model has to represent precisely the mechanical construction of the CMA. Thus, a reliable and accurate calibration is essential...

Erfassung zeitlicher Veränderungen aus Punktwolkenepochen

In terms of high precision requested deformation analyses, evaluating laser scan data requires the exact knowledge of the functional and stochastic model. If this is not given, a parameter estimation leads to insufficient results. Simulating a laser scanning scene provides the knowledge of the exact functional model of the surface. Thus, it is poss...