scholarly journals The New Approach to Camera Calibration – GCPs or TLS Data?

2016 ◽  
Vol XLI-B3 ◽  
pp. 75-82
Author(s):  
J. Markiewicz ◽  
P. Podlasiak ◽  
M. Kowalczyk ◽  
D. Zawieska
Keyword(s):  
Camera Calibration ◽  
Laser Scanning ◽  
Laser Scanner ◽  
Automatic Identification ◽  
Test Field ◽  
Control Points ◽  
Data Set ◽  
Laser Measurements ◽  
Close Range ◽  
Processed Products

Camera calibration is one of the basic photogrammetric tasks responsible for the quality of processed products. The majority of calibration is performed with a specially designed test field or during the self-calibration process. The research presented in this paper aims to answer the question of whether it is necessary to use control points designed in the standard way for determination of camera interior orientation parameters. Data from close-range laser scanning can be used as an alternative. The experiments shown in this work demonstrate the potential of laser measurements, since the number of points that may be involved in the calculation is much larger than that of commonly used ground control points. The problem which still exists is the correct and automatic identification of object details in the image, taken with a tested camera, as well as in the data set registered with the laser scanner.

scholarly journals The New Approach to Camera Calibration – GCPs or TLS Data?

2016 ◽  
Vol XLI-B3 ◽  
pp. 75-82
Author(s):  
J. Markiewicz ◽  
P. Podlasiak ◽  
M. Kowalczyk ◽  
D. Zawieska
Keyword(s):  
Camera Calibration ◽  
Laser Scanning ◽  
Laser Scanner ◽  
Automatic Identification ◽  
Test Field ◽  
Control Points ◽  
Data Set ◽  
Laser Measurements ◽  
Close Range ◽  
Processed Products

Camera calibration is one of the basic photogrammetric tasks responsible for the quality of processed products. The majority of calibration is performed with a specially designed test field or during the self-calibration process. The research presented in this paper aims to answer the question of whether it is necessary to use control points designed in the standard way for determination of camera interior orientation parameters. Data from close-range laser scanning can be used as an alternative. The experiments shown in this work demonstrate the potential of laser measurements, since the number of points that may be involved in the calculation is much larger than that of commonly used ground control points. The problem which still exists is the correct and automatic identification of object details in the image, taken with a tested camera, as well as in the data set registered with the laser scanner.

scholarly journals Development of 3D environmental laser scanner using pinhole projection

2021 ◽  
Vol 2 (1 (110)) ◽  
pp. 37-43
Author(s):  
Lateef Abd Zaid Qudr
Keyword(s):  
Camera Calibration ◽  
Laser Scanning ◽  
Focal Length ◽  
Laser Scanner ◽  
Optical Center ◽  
Calibration Error ◽  
Scanning System ◽  
Fast Method ◽  
Actual Measurement ◽  
Close Range

Three-dimensional (3D) information of capturing and reconstructing an object existing in its environment is a big challenge. In this work, we discuss the 3D laser scanning techniques, which can obtain a high density of data points by an accurate and fast method. This work considers the previous developments in this area to propose a developed cost-effective system based on pinhole projection concept and commercial hardware components taking into account the current achieved accuracy. A laser line auto-scanning system was designed to perform close-range 3D reconstructions for home/office objects with high accuracy and resolution. The system changes the laser plane direction with a microcontroller to perform automatic scanning and obtain continuous laser strips for objects’ 3D reconstruction. The system parameters were calibrated with Matlab’s built-in camera calibration toolbox to find camera focal length and optical center constraints. The pinhole projection equation was defined to optimize the prototype rotating axis equation. The developed 3D environmental laser scanner with pinhole projection proved the system’s effectiveness on close-range stationary objects with high resolution and accuracy with a measurement error in the range (0.05–0.25) mm. The 3D point cloud processing of the Matlab computer vision toolbox has been employed to show the 3D object reconstruction and to perform the camera calibration, which improves efficiency and highly simplifies the calibration method. The calibration error is the main error source in the measurements, and the errors of the actual measurement are found to be influenced by several environmental parameters. The presented platform can be equipped with a system of lower power consumption, and compact smaller size

scholarly journals FINE REGISTRATION OF KILO-STATION NETWORKS - A MODERN PROCEDURE FOR TERRESTRIAL LASER SCANNING DATA SETS

2016 ◽  
Vol XLI-B5 ◽  
pp. 485-492
Author(s):  
J.-F. Hullo
Keyword(s):  
Laser Scanning ◽  
Laser Scanner ◽  
Data Sets ◽  
Data Set ◽  
Information Models ◽  
3D Network ◽  
Laser Scanners ◽  
Building Information ◽  
Set Up ◽  
Fine Registration

We propose a complete methodology for the fine registration and referencing of kilo-station networks of terrestrial laser scanner data currently used for many valuable purposes such as 3D as-built reconstruction of Building Information Models (BIM) or industrial asbuilt mock-ups. This comprehensive target-based process aims to achieve the global tolerance below a few centimetres across a 3D network including more than 1,000 laser stations spread over 10 floors. This procedure is particularly valuable for 3D networks of indoor congested environments. In situ, the use of terrestrial laser scanners, the layout of the targets and the set-up of a topographic control network should comply with the expert methods specific to surveyors. Using parametric and reduced Gauss-Helmert models, the network is expressed as a set of functional constraints with a related stochastic model. During the post-processing phase inspired by geodesy methods, a robust cost function is minimised. At the scale of such a data set, the complexity of the 3D network is beyond comprehension. The surveyor, even an expert, must be supported, in his analysis, by digital and visual indicators. In addition to the standard indicators used for the adjustment methods, including Baarda’s reliability, we introduce spectral analysis tools of graph theory for identifying different types of errors or a lack of robustness of the system as well as <i>in fine</i> documenting the quality of the registration.

scholarly journals THE FACADE’S DOME OF THE ST. ANTHONY’S BASILICA IN PADUA

2019 ◽  
Vol XLII-2/W11 ◽  
pp. 481-487 ◽  
Author(s):  
M. Diaz ◽  
S. M. Holzer
Keyword(s):  
Data Processing ◽  
Laser Scanning ◽  
Laser Scanner ◽  
Complex Structures ◽  
Modus Operandi ◽  
Time Consumption ◽  
Stratigraphic Analysis ◽  
Entire Structure ◽  
Close Range ◽  
Human Effort

<p><strong>Abstract.</strong> The basilica of St. Anthony in Padua (13th–14th cent.) is one of the most remarkable pilgrimage sites in Italy. To date, the monument itself has never been subject to a comprehensive stratigraphic analysis. Important information about the construction sequence of the building may be conserved in the domed roofs protecting the inner masonry shells.</p><p>The present paper will focus on the dome next to the facade. During the survey, data acquisition via laser scanner have been flanked by standard tasks. Specifically, the stratification analysis of the timber framework of the dome requires to measure the entire structure, including parts with difficult access, and calls for many scan bases to go further the sight obstacles represented by the rafters and the horizontal collar-beams. Therefore, application of laser scanning might appear difficult at first sight.</p><p>The authors will show that the approach confirms the suitability of the laser scanner technology in facing the general complexity of the structure. The development of a graphic documentation in CAD environment entailed a manageable complexity in terms of time-consumption and precision in data processing. So far, the plans reveal the irregular profile of the dome in its inner masonry shell, and of the outer masonry drum. The sections show a two-centre curvature of the elevation of the outer timber shell. However, the joints among the rafters, ribs, and tie-beams still require a series of traditional in-depth assessments acquired in close-range access.</p><p>Nevertheless, the pragmatic investigative modus operandi, tested up to now, does represent a fixed protocol suitable to be iterated and perfected for each cupola. In such complex structures, the laser scanning process confirms to be a valid strategy to reach a good compromise between time consumption, human effort, and millimetre precision. In this way, the collected material provides a first contribution to acquire knowledge on this Italian medieval masterpiece, which stands out on the international scenario for its historical richness and architectural complexity.</p>

scholarly journals Terrestrial Laser Scanning and Settled Techniques: A Support to Detect Pathologies and Safety Conditions of Timber Structures

2013 ◽  
Vol 778 ◽  
pp. 350-357 ◽  
Author(s):  
Clara Bertolini-Cestari ◽  
Filiberto Chiabrando ◽  
Stefano Invernizzi ◽  
Tanja Marzi ◽  
Antonia Spanò
Keyword(s):  
Laser Scanning ◽  
Planning Process ◽  
Laser Scanner ◽  
Texture Mapping ◽  
Surface Model ◽  
Resolution Model ◽  
Close Range ◽  
High Resolution Model ◽  
Increasing Demand ◽  
Non Destructive

Nowadays, there is an increasing demand for detailed geometrical representation of the existing cultural heritage, in particular to improve the comprehension of interactions between different phenomena and to allow a better decisional and planning process. The LiDAR technology (Light Detection and Ranging) can be adopted in different fields, ranging from aerial applications to mobile and terrestrial mapping systems. One of the main target of this study is to propose an integration of innovative and settled inquiring techniques, ranging from the reading of the technological system, to non-destructive tools for diagnosis and 3D metric modeling of buildings heritage. Many inquiring techniques, including Terrestrial Laser Scanner (TLS) method, have been exploited to study the main room of the Valentino Castle in Torino. The so-called “Salone delle Feste”, conceived in the XVIIth century under the guidance of Carlo di Castellamonte, has been selected as a test area. The beautiful frescos and stuccoes of the domical vault are sustained by a typical Delorme carpentry, whose span is among the largest of their kind. The dome suffered from degradation during the years, and a series of interventions were put into place. A survey has revealed that the suspender cables above the vault in the region close to the abutments have lost their tension. This may indicate an increase of the vault deformation; therefore a structural assessment of the dome is mandatory. The high detailed metric survey, carried out with integrated laser scanning and digital close range photogrammetry, reinforced the structural hypothesis of damages and revealed the deformation effects. In addition, the correlation between the survey-model of the intrados and of the extrados allowed a non-destructive and extensive determination of the dome thickness. The photogram-metrical survey of frescos, with the re-projection of images on vault surface model (texture mapping), is purposed to exactly localize formers restoration and their signs on frescos continuity. The present paper illustrates the generation of the 3D high-resolution model and its relations with the results of the structural survey; both of them support the Finite Element numerical simulation of the dome.

scholarly journals IMAGING OF CORROSION PITS ON METALLIC PIPES USING A LASER SCANNER

2011 ◽  
Author(s):  
Homayoun Najjaran
Keyword(s):  
Laser Scanning ◽  
Laser Scanner ◽  
Scanning Speed ◽  
Displacement Sensor ◽  
Statistical Characteristics ◽  
Measuring Instruments ◽  
Scanning System ◽  
Laser Measurements ◽  
Corrosion Pits ◽  
Pit Depth

This paper describes the hardware and software of a laser scanning system that is used to produce 3D images of external surfaces of pipes. The images are produced in the form of 3D raster images with a resolution of up to 0.1×0.1 mm and an accuracy of 3-10 microns, depending on the desired scanning speed, to portray the corrosion pits on the pipes. The main application of the scanner is to establish patterns for calibrating nondestructive testing techniques (e.g., Remote Field Eddy Current (RFEC) and ultrasound testing that are commonly used to measure the remaining wall thickness of ductile and cast iron pipes), and also identifying the statistical characteristics of the measuring instruments utilized in those methods. The images may also be useful to scrutinize corrosion and failure mechanisms, especially when estimates of average or maximum pit depth are insufficient. The scanning system consists of a 2-DOF robot that can move a laser displacement sensor along a pipe and an instrumented rig that rotates the pipe about its axis. Rotating the pipe and moving the rangefinder along the pipe’s axis, the scanning system acquires laser measurements into a host computer to produce the image. The paper also presents the images and statistical analysis of corrosion pits of pipe samples exhumed and sandblasted for scanning.

scholarly journals ONLY IMAGE BASED FOR THE 3D METRIC SURVEY OF GOTHIC STRUCTURES BY USING FRAME CAMERAS AND PANORAMIC CAMERAS

2016 ◽  
Vol XLI-B5 ◽  
pp. 363-370 ◽  
Author(s):  
A. Pérez Ramos ◽  
G. Robleda Prieto
Keyword(s):  
Laser Scanning ◽  
Imaging Techniques ◽  
Laser Scanner ◽  
Point Clouds ◽  
Office Work ◽  
Light Conditions ◽  
External Quality ◽  
Panoramic Cameras ◽  
Dense Point ◽  
Close Range

Indoor Gothic apse provides a complex environment for virtualization using imaging techniques due to its light conditions and architecture. Light entering throw large windows in combination with the apse shape makes difficult to find proper conditions to photo capture for reconstruction purposes. Thus, documentation techniques based on images are usually replaced by scanning techniques inside churches. Nevertheless, the need to use Terrestrial Laser Scanning (TLS) for indoor virtualization means a significant increase in the final surveying cost. So, in most cases, scanning techniques are used to generate dense point clouds. However, many Terrestrial Laser Scanner (TLS) internal cameras are not able to provide colour images or cannot reach the image quality that can be obtained using an external camera. Therefore, external quality images are often used to build high resolution textures of these models. This paper aims to solve the problem posted by virtualizing indoor Gothic churches, making that task more affordable using exclusively techniques base on images. It reviews a previous proposed methodology using a DSRL camera with 18-135 lens commonly used for close range photogrammetry and add another one using a HDR 360° camera with four lenses that makes the task easier and faster in comparison with the previous one. Fieldwork and office-work are simplified. The proposed methodology provides photographs in such a good conditions for building point clouds and textured meshes. Furthermore, the same imaging resources can be used to generate more deliverables without extra time consuming in the field, for instance, immersive virtual tours. In order to verify the usefulness of the method, it has been decided to apply it to the apse since it is considered one of the most complex elements of Gothic churches and it could be extended to the whole building.

scholarly journals IMPACT OF DIFFERENT TRAJECTORIES ON EXTRINSIC SELF-CALIBRATION FOR VEHICLE-BASED MOBILE LASER SCANNING SYSTEMS

2019 ◽  
Vol XLII-2/W16 ◽  
pp. 119-125
Author(s):  
M. Hillemann ◽  
J. Meidow ◽  
B. Jutzi
Keyword(s):  
Laser Scanning ◽  
Laser Scanner ◽  
Relative Orientation ◽  
Scanning System ◽  
Confined Space ◽  
Data Set ◽  
Self Calibration ◽  
Yaw Angle ◽  
Laser Scanning System ◽  
The Impact

<p><strong>Abstract.</strong> The extrinsic calibration of a Mobile Laser Scanning system aims to determine the relative orientation between a laser scanner and a sensor that estimates the exterior orientation of the sensor system. The relative orientation is one component that limits the accuracy of a 3D point cloud which is captured with a Mobile Laser Scanning system. The most efficient way to determine the relative orientation of a Mobile Laser Scanning system is using a self-calibration approach as this avoids the need to perform an additional calibration beforehand. Instead, the system can be calibrated automatically during data acquisition. The entropy-based self-calibration fits into this category and is utilized in this contribution. In this contribution, we analyze the impact of four different trajectories on the result of the entropy-based self-calibration, namely (i) uni-directional, (ii) ortho-directional, (iii) bi-directional, and (iv) multi-directional trajectory. Theoretical considerations are supported by experiments performed with the publicly available <i>MLS 1 – TUM City Campus</i> data set. The investigations show that strong variations of the yaw angle in a confined space or bidirectional trajectories as well as the variation of the height of the laser scanner are beneficial for calibration.</p>

scholarly journals Applicability Assessments of Close-Range Photogrammetry for Slope Face 3D Modelling

2020 ◽  
Vol 8 (3) ◽  
pp. 143-150
Author(s):  
Haqul Baramsyah ◽  
Less Rich
Keyword(s):  
Laser Scanning ◽  
3D Model ◽  
Laser Scanner ◽  
Cost Effective ◽  
3D Models ◽  
Digital Photogrammetry ◽  
Aerial Photogrammetry ◽  
3D Data ◽  
Image Capturing ◽  
Close Range

The digital single lens reflex (DSLR) cameras have been widely accepted to use in slope face photogrammetry rather than the expensive metric camera used for aerial photogrammetry. 3D models generated from digital photogrammetry can approach those generated from terrestrial laser scanning in term of scale and level of detail. It is cost effective and has equipment portability. This paper presents and discusses the applicability of close-range digital photogrammetry to produce 3D models of rock slope faces. Five experiments of image capturing method were conducted to capture the photographs as the input data for processing. As a consideration, the appropriate baseline lengths to capture the slope face to get better result are around 1/6 to 1/8 of target distance.  A fine quality of 3D model from data processing is obtained using strip method and convergent method with 80% overlapping in each photograph. A random camera positions with different distances from the slope face can also generate a good 3D model, however the entire target should be captured in each photograph. The accuracy of the models is generated by comparing the 3D models produced from photogrammetry with the 3D data obtained from laser scanner. The accuracy of 3D models is quite satisfactory with the mean error range from 0.008 to 0.018 m.

scholarly journals Influence of Control Points Configuration on the Mobile Laser Scanning Accuracy

2021 ◽  
Vol 906 (1) ◽  
pp. 012091
Author(s):  
Petr Kalvoda ◽  
Jakub Nosek ◽  
Petra Kalvodova
Keyword(s):  
Reference Point ◽  
Point Cloud ◽  
Laser Scanning ◽  
Reference Data ◽  
Data Sets ◽  
Control Points ◽  
Mobile Mapping ◽  
Data Set ◽  
Accuracy Test ◽  
Data Subset

Abstract Mobile mapping systems (MMS) are becoming widely used in standard geodetic tasks more commonly in the last years. The paper is focused on the influence of control points (CPs) number and configuration on mobile laser scanning accuracy. The mobile laser scanning (MLS) data was acquired by MMS RIEGL VMX-450. The resulting point cloud was compared with two different reference data sets. The first reference data set consisted of a high-accuracy test point field (TPF) measured by a Trimble R8s GNSS system and a Trimble S8 HP total station. The second reference data set was a point cloud from terrestrial laser scanning (TLS) using two Faro Focus3D X 130 laser scanners. The coordinates of both reference data sets were determined with significantly higher accuracy than the coordinates of the tested MLS point cloud. The accuracy testing is based on coordinate differences between the reference data set and the tested MLS point cloud. There is a minimum number of 6–7 CPs in our scanned area (based on MLS trajectory length) to achieve the declared relative accuracy of trajectory positioning according to the RIEGL datasheet. We tested two types of ground control point (GCP) configurations for 7 GCPs, using TPF reference data. The first type is a trajectory-based CPs configuration, and the second is a geometry-based CPs configuration. The accuracy differences of the MLS point clouds with trajectory-based CPs configuration and geometry-based CPs configuration are not statistically significant. From a practical perspective, a geometry-based CPs configuration is more advantageous in the nonlinear type of urban area such as our one. The following analyzes are performed on geometry-based CPs configuration variants. We tested the influence of changing the location of two CPs from ground to roof. The effect of the vertical configuration of the CPs on the accuracy of the tested MLS point cloud has not been demonstrated. The effect of the number of control points on the accuracy of the MLS point cloud was also tested. In the overall statistics using TPF, the accuracy increases significantly with increasing the number of GCPs up to 6. This number corresponds to a requirement of the manufacturer. Although further increasing the number of CPs does not significantly increase the global accuracy, local accuracy improves with increasing the number of CPs up to 10 (average spacing 50 m) according to the comparison with the TLS reference point cloud. The accuracy test of the MLS point cloud was divided into the horizontal accuracy test on the façade data subset and the vertical accuracy test on the road data subset using the TLS reference point cloud. The results of this paper can help improve the efficiency and accuracy of the mobile mapping process in geodetic praxis.

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