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Lightweight materials, such as titanium alloys, magnesium alloys, and aluminium alloys, are characterised by unusual combinations of high strength, corrosion resistance, and low weight. However, some of the grades of these alloys exhibit poor formability at room temperature, which limits their application in sheet metal-forming processes. Lightweight materials are used extensively in the automobile and aerospace industries, leading to increasing demands for advanced forming technologies. This article presents a brief overview of state-of-the-art methods of incremental sheet forming (ISF) for lightweight materials with a special emphasis on the research published in 2015–2021. First, a review of the incremental forming method is provided. Next, the effect of the process conditions (i.e., forming tool, forming path, forming parameters) on the surface finish of drawpieces, geometric accuracy, and process formability of the sheet metals in conventional ISF and thermally-assisted ISF variants are considered. Special attention is given to a review of the effects of contact conditions between the tool and sheet metal on material deformation. The previous publications related to emerging incremental forming technologies, i.e., laser-assisted ISF, water jet ISF, electrically-assisted ISF and ultrasonic-assisted ISF, are also reviewed. The paper seeks to guide and inspire researchers by identifying the current development trends of the valuable contributions made in the field of SPIF of lightweight metallic materials.

Introduction: As the prognosis of early-stage breast cancer patients is excellent, prevention of radiation induced toxicity has become crucial. Reduction of margins compensating for intrafraction motion reduces non-target dose. We assessed motion of the tumor bed throughout APBI treatment fractions and calculated CTV-PTV margins for breathing and drift.Methods: This prospective clinical trial included patients treated with APBI on a Cyberknife with fiducial tracking. Paired orthogonal kV images made throughout the entire fraction were used to extract the tumor bed position. The images used for breathing modelling were used to calculate breathing amplitudes. The margins needed to compensate for breathing and drift were calculated according to Engelsman and Van Herk respectively.Results: Twenty-two patients, 110 fractions and 5087 image pairs were analyzed. The margins needed for breathing were 0.3-0.6 mm. The margin for drift increased with time after the first imaging for positioning. For a total fraction duration up to 8 min, a margin of 1.0 mm is sufficient. For a fraction of 32 min, 2.5 mm is needed. Techniques that account for breathing motion can reduce the margin by 0.1 mm. There was a systematic trend in the drift in the caudal, medial and posterior direction. To compensate for this, 0.7 mm could be added to the margins.Conclusions: The margin needed to compensate for intrafraction motion increased with longer fraction duration due to drifting of the target. It doubled for a fraction of 24 min compared to 8 min. Breathing motion has a limited effect.(c) 2021 The Authors. Published by Elsevier B.V. Radiotherapy and Oncology 159 (2021) 176-182 This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Additive manufacturing (AM), also known as 3D printing, has gained significant interest due to the freedom it offers in creating complex-shaped and highly customized parts with little lead time. However, a current challenge of AM is the lack of geometric accuracy of fabricated parts. To improve the geometric accuracy of 3D printed parts, this paper presents a three-dimensional geometric compensation method that allows for eliminating systematic deviations by morphing the original surface mesh model of the part by the inverse of the systematic deviations. These systematic deviations are measured by 3D scanning multiple sacrificial printed parts and computing an average deviation vector field throughout the model. We demonstrate the necessity to filter out the random deviations from the measurement data used for compensation. Case studies demonstrate that printing the compensated mesh model based on the average deviation of five sacrificial parts produces a part with deviations about three times smaller than measured on the uncompensated parts. The deviation values of this compensated part based on the average deviation vector field are less than half of the deviation values of the compensated part based on only one sacrificial part.

In the field of Cultural Heritage preservation and enhancement, detecting objects quickly and inexpensively, with the possibility of repeating measurements several times for monitoring any deterioration, has become an increasingly significant requirement. The existence of a conspicuous historical heritage across the Italian territory often forces local authorities to orient their survey strategies towards the research of the most economic, but still efficient, solutions. Due to these reasons, also in consideration of possible emergency situations, it is necessary to find the optimal solution to allow a timely and comprehensive detection of exhaustive 3D digital object reconstructions. An important task is therefore to test the potential accuracies of recent measurement technologies and procedures in order to produce high quality results. This study analyzes the generation of three-dimensional reconstructions of Torre Zozzoli, an historic fortified tower located 25 km from Taranto (Apulia region, Italy), through two close-range detection techniques, by comparing Terrestrial Laser Scanner (TLS) and Unmanned Aerial Vehicles (UAVs) photogrammetric imagery. To arrange and improve the methodologies of ground control point measurements, two survey techniques were implemented by means of a Total Station (TS) and a GNSS receiver in nRTK mode. Lastly, using the cloud-to-cloud (C2C) comparison tools and implementing three distributions of GCPs, UAVs and TLS points clouds were compared. Considering their accessibility in terms of costs and use, photogrammetric products from UAVs, represent a valid alternative to TLS-based 3D data in multi-temporal analysis.

Inter-operational surgery supplies manufactured additively using the FDM (Fused Deposition Modelling) technology are required to be sterilized before use. After manufacturing, the part should be sterilized using one of commonly used processes, without losing its dimensions and shape. The paper presents studies on manufacturing and sterilizing samples made out of ABS material and influence of the sterilization process on the dimensional accuracy of these samples.

Magnetic Resonance Imaging (MRI) is increasingly being used for improving tumor delineation and tumor tracking in the presence of respiratory motion. The purpose of this work is to design and build an MR compatible motion platform and to use it for evaluating the geometric accuracy of MR imaging techniques during respiratory motion. The motion platform presented in this work is composed of a mobile base made up of a flat plate and four wheels. The mobile base is attached from one end and through a rigid rod to a synchrony motion table by Accuray® placed at the end of the MRI table and from the other end to an elastic rod. The geometric accuracy was measured by placing a control point‐based phantom on top of the mobile base. In‐house software module was used to automatically assess the geometric distortion. The blurring artifact was also assessed by measuring the Full Width Half Maximum (FWHM) of each control point. Our results were assessed for 50, 100, and 150 mm radial distances, with a mean geometric distortion during the superior–inferior motion of 0.27, 0.41, and 0.55 mm, respectively. Adding the anterior–posterior motion, the mean geometric distortions increased to 0.4, 0.6, and 0.8 mm. Blurring was observed during motion causing an increase in the FWHM of ≈30%. The platform presented in this work provides a valuable tool for the assessment of the geometric accuracy and blurring artifact for MR during motion. Although the main objective was to test the spatial accuracy of an MR system during motion, the modular aspect of the presented platform enables the use of any commercially available phantom for a full quality control of the MR system during motion.

Purpose The purpose of this paper is to discuss the problem of the geometric accuracy of edges in parts manufactured by the Fused Deposition Modeling process, as a preliminary step for an experimental investigation. Methodology/approach Three geometric variables (inclination, included and incidence angles) were defined for an edge. The influence of each variable on the geometric errors was explained with reference to specific causes related to physical phenomena and process constraints. Findings Occurrence conditions for all causes were determined and visualized in a process map, which was also developed into a software procedure for the diagnosis of quality issues on digital models of the parts. Research limitations/implications The process map was developed by only empirical considerations and does not allow to predict the amount of geometric errors. In the second part of the paper, experimental tests will help to extend and validate the prediction criteria. Practical implications As demonstrated by an example, the results allow to predict the occurrence of visible defects on the edges of a part before manufacturing it with a given build orientation. Originality/value In literature, the geometric accuracy of additively manufactured parts is only related to surface features. The paper shows that the quality of edges depends on additional variables and causes to be carefully controlled by process choices.

The present work focuses on the manufacturing of Ti-6Al-4V parts using hot single point incremental forming (SPIF), a non-conventional forming technology mainly oriented toward the fabrication of prototypes, spare parts, or very low volume series. In the used procedure, the entire sheet is heated and kept at uniform temperature while the tool incrementally forms the part, with the limited accuracy of the obtained parts being the major drawback of the process. Thus, this work proposes two approaches to improve the geometric accuracy of Ti-6Al-4V SPIF parts: (i) correct the tool path by applying an intelligent process model (IPM) that counteracts deviations associated with the springback, and (ii) skip overforming deviations associated with the deflection of the sheet along the perimeter of the part based on a design improvement. For this purpose, a generic asymmetric design that incorporates features of a typical aerospace Ti-6Al-4V part is used. The results point out the potential of both solutions to significantly improve the accuracy of the parts. The application of the IPM model leads to an accuracy improvement up to 49%, whereas a 25.4% improvement can be attributed to the addendum introduction. The geometric accuracy study includes the two finishing operations needed to obtain the part, namely decontamination and trimming. Research leading to these results was done within the project INMA—Innovative manufacturing of complex titanium sheet components. This research was funded by the European Union´s Seventh Framework Programme for research, technological development, and demonstration under grant agreement number 266208.

Geometric calibration is an important means of improving the absolute positioning accuracy of space-borne synthetic aperture radar imagery. The conventional calibration method is based on a calibration field, which is simple and convenient, but requires a great deal of manpower and material resources to obtain ground control points. Although newer cross-calibration methods do not require ground control points, calibration accuracy still depends on a periodically updated reference image. Accordingly, this study proposes a geometric self-calibration method based on the positioning consistency constraint of conjugate image points to provide rapid and accurate calibration of the YaoGan-13 satellite. The proposed method can accurately calibrate geometric parameters without requiring ground control points or high-precision reference images. To verify the absolute positioning accuracy obtained using the proposed self-calibration method, YaoGan-13 Stripmap images of multiple regions were collected and evaluated. The results indicate that high-accuracy absolute positioning can be achieved with a plane accuracy of 3.83 m or better for Stripmap data, without regarding elevation error. Compared to the conventional calibration method using high-accuracy control data, the difference between the two methods is only about 2.53 m, less than the 3-m resolution of the image, verifying the effectiveness of the proposed self-calibration method.

© 2019 American Association of Physicists in Medicine Purpose: Kilovoltage intrafraction monitoring (KIM) allows for real-time image guidance for tracking tumor motion in six-degrees-of-freedom (6DoF) on a standard linear accelerator. This study assessed the geometric accuracy and precision of KIM used to guide patient treatments in the TROG 15.01 multi-institutional Stereotactic Prostate Ablative Radiotherapy with KIM trial and investigated factors affecting accuracy and precision. Methods: Fractions from 44 patients with prostate cancer treated using KIM-guided SBRT were analyzed across four institutions, on two different linear accelerator models and two different beam models (6 MV and 10 MV FFF). The geometric accuracy and precision of KIM was assessed from over 33 000 images (translation) and over 9000 images (rotation) by comparing the real-time measured motion to retrospective kV/MV triangulation. Factors potentially affecting accuracy, including contrast-to-noise ratio (CNR) of kV images and incorrect marker segmentation, were also investigated. Results: The geometric accuracy and precision did not depend on treatment institution, beam model or motion magnitude, but was correlated with gantry angle. The centroid geometric accuracy and precision of the KIM system for SABR prostate treatments was 0.0 ± 0.5, 0.0 ± 0.4 and 0.1 ± 0.3 mm for translation, and −0.1 ± 0.6°, −0.1 ± 1.4° and −0.1 ± 1.0° for rotation in the AP, LR and SI directions respectively. Centroid geometric error exceeded 2 mm for 0.05% of this dataset. No significant relationship was found between large geometric error and CNR or marker segmentation correlation. Conclusions: This study demonstrated the ability of KIM to locate the prostate with accuracy below other uncertainties in radiotherapy treatments, and the feasibility for KIM to be implemented across multiple institutions.

This paper provides geometric accuracy improvements for very high resolution WorldView‐2 (WV2) Ortho Ready Standard Level‐2A (ORS2A) satellite images in the panchromatic (PAN) band. The entire process can be divided into two steps: (1) sensor orientation, which was conducted on 40 ground control points (GCPs) to determine which sensor model was best depending on various numbers of GCPs ; and (2) orthorectification, whose main objective was to compare the accuracy of the process when using different freely available global digital elevation models (DEMs). The research showed that a sensor model based on rational polynomial coefficients (RPCs) with a shift or zero‐ order bias correction attained the best geopositioning accuracy during the orientation step with the use of seven GCPs. The highest accuracy was achieved for images orthorectified with the ALOS World 3D‐30 m DEM (AW3D30).

Assessing the quality of construction for compliance with the design intent has been a challenging task in the AEC (Architecture, Engineering, and Construction) industry. As modern design methods using Building Information Modeling (BIM) techniques have been increasingly adopted by the AEC industry, construction quality assessment using BIM has become a challenging new task for practitioners. In the past few years, 3D as-built models for construction quality assessment have been developed using data acquisition techniques like 3D laser scanning and photogrammetry. However, certain limitations like non-affordability, requiring expertise to operate, and dependence on time-consuming processes are restricting their usage for construction quality control purposes. The main objective of this work is to study the applicability of using a new, affordable, easy to use, and faster modeling technology (Project Tango) to produce 3D as-built models for facilitating the construction quality control process. For this purpose, a construction project was chosen as a case study and three different scenarios (including interior and exterior environments) were modelled using Project Tango. A post-processing method was developed to prepare the scanned as-built models for comparison with the design BIM. The accuracy level of these as-built models were also evaluated using dimension accuracy analysis. The prepared as-built models and the design BIM were then integrated and adjusted in the Autodesk Navisworks environment to perform the quality control assessment. This assessment process includes object completeness testing and spatial deviation analyses. This research thus highlights both the advantages and limitations of Project Tango and shows that such technologies have a great potential for construction quality assessments.

Mapping landscape change at detailed scales is an interesting task when the focus is not only the land cover change. The paper proposes the integration of a diachronic imagery set in a GIS application in order to obtain precise maps of the key qualitative changes along a representative sector of the Danube River Defile where the Iron Gates emerged between 1965-1972 to the border between Romania and Serbia. A photogrammetric process approach was developed for the building of precise historical orthophoto coverage on the basis of a CORONA KH-4B/ DECLASS-1 dataset. This was focused on reconstructing the image geometry and building a precise orientation, together with an aerial triangulation operation. The results were a Digital Surface Model and an orthophoto (about 5 m average geometric accuracy). This data was integrated into a GIS project with vector data extracted from the latest orthophotos (0.5 m, by ANCPI Bucharest) for mapping of landscape changes as an effect of the complex hydrotechnical works. The Iron Gates reservoir level was of about +33 m higher at the beginning of the 1970s in comparison with the primary Danube River level, the road and the railroad moved upslope like Orsova town and other villages. The most dramatic change was related to the total flooding of Ada-Kaleh Island with a Turkish settlement and a Vauban system fortress, an interesting historical and cultural site.

Geometric dimensions of plants are significant parameters for showing plant dynamic responses to environmental variations. An image-based high-throughput phenotyping platform was developed to automatically measure geometric dimensions of plants in a greenhouse. The goal of this paper was to evaluate the accuracy in geometric measurement using the Structure from Motion (SfM) method from images acquired using the automated image-based platform. Images of nine artificial objects of different shapes were taken under 17 combinations of three different overlaps in x and y directions, respectively, and two different spatial resolutions (SRs) with three replicates. Dimensions in x, y and z of these objects were measured from 3D models reconstructed using the SfM method to evaluate the geometric accuracy. A metric power of unit (POU) was proposed to combine the effects of image overlap and SR. Results showed that measurement error of dimension in z is the least affected by overlap and SR among the three dimensions and measurement error of dimensions in x and y increased following a power function with the decrease of POU (R2 = 0.78 and 0.88 for x and y respectively). POUs from 150 to 300 are a preferred range to obtain reasonable accuracy and efficiency for the developed image-based high-throughput phenotyping system. As a study case, the developed system was used to measure the height of 44 plants using an optimal POU in greenhouse environment. The results showed a good agreement (R2 = 92% and Root Mean Square Error = 9.4 mm) between the manual and automated method.

The recent development and proliferation of Unmanned Aircraft Systems (UASs) has made it possible to examine environmental processes and changes occurring at spatial and temporal scales that would be difficult or impossible to detect using conventional remote sensing platforms. However, new methodologies need to be codified in order to be compared with traditional photogrammetric products. This can be done by testing geometrical accuracies reached by the models when external orientations have changed. In this paper two dense point clouds, derived from the same spatial database, were compared to evaluate the discrepancies resulting from two different relative orientations: the first one based on the GPS position of each UAV frame and the second one based on GCPs, measured through GNSS positioning. The two dense point clouds presented an average offset of 3.4 cm and a standard deviation of 5 cm, proving that relative accuracy is only influenced by the matching intensity. To assign three different absolute orientations, the georeferencing procedure of the same orthomosaic was then verified based on GCPs coming from three different open geo-data sources. By evaluating the position discrepancies of some Independent Check Points (ICPs), the three open geo-data sources provided three estimates of different root-mean-square error (RMSE) positional accuracy, of which the absolute geometrical precision was the related function.

While impressive direct geolocation accuracies better than 5.0 m CE90 (90% of circular error) can be achieved from the last DigitalGlobe’s Very High Resolution (VHR) satellites (i.e. GeoEye-1 and WorldView-1/2/3/4), it is insufficient for many precise geodetic applications. For these sensors, the best horizontal geopositioning accuracies (around 0.55 m CE90) can be attained by using third-order 3D rational functions with vendor’s rational polynomial coefficients data refined by a zero-order polynomial adjustment obtained from a small number of very accurate ground control points (GCPs). However, these high-quality GCPs are not always available. In this work, two different approaches for improving the initial direct geolocation accuracy of VHR satellite imagery are proposed. Both of them are based on the extraction of three-dimensional GCPs from freely available ancillary data at global coverage such as multi-temporal information of Google Earth and the Shuttle Radar Topography Mission 30 m digital elevation model. The application of these approaches on WorldView-2 and GeoEye-1 stereo pairs over two different study sites proved to improve the horizontal direct geolocation accuracy values around of 75%.

Attitude data, which is the important data strongly correlated with the geometric accuracy of optical remote sensing satellite images, are generally obtained using a real-time Extended Kalman Filter (EKF) with star-tracker and gyro data for current high-resolution satellites, such as Orb-view, IKONOS, Quickbird,Pleiades, and ZY-3.We propose a forward-backward Unscented Kalman Filter (UKF) for post-processing, and the proposed method employs UKF to suppress noise by using an unscented transformation (UT) rather than an EKF in a nonlinear attitude system. Moreover, this method makes full use of the collected data in the fixed-interval and computational resources on the ground, and it determines optimal attitude results by forward-backward filtering and weighted smoothing with the raw star-tracker and gyro data collected for a fixed period. In this study, the principle and implementation of the proposed method are described. The post-processed attitude was compared with the on-board attitude, and the absolute accuracy was evaluated by the two methods. One method compares the positioning accuracy of the object space coordinates with the post-processed and on-board attitude data without using ground control points (GCPs). The other method compares the tie-point residuals of the image coordinates after a free net adjustment. In addition, the internal and external parameters of the camera were accurately calibrated before use for an objective evaluation of the attitude accuracy. The experimental results reveal that the accuracy of the post-processed attitude is superior to the accuracy of the on-board processed attitude. This method has been applied to the ZiYuan-3 satellite system for processing the raw star-tracker and gyro data daily.

The Landsat 8 spacecraft was launched on 11 February 2013 carrying the Operational Land Imager (OLI) payload for moderate resolution imaging in the visible, near infrared (NIR), and short-wave infrared (SWIR) spectral bands. During the 90-day commissioning period following launch, several on-orbit geometric calibration activities were performed to refine the prelaunch calibration parameters. The results of these calibration activities were subsequently used to measure geometric performance characteristics in order to verify the OLI geometric requirements. Three types of geometric calibrations were performed including: (1) updating the OLI-to-spacecraft alignment knowledge; (2) refining the alignment of the sub-images from the multiple OLI sensor chips; and (3) refining the alignment of the OLI spectral bands. The aspects of geometric performance that were measured and verified included: (1) geolocation accuracy with terrain correction, but without ground control (L1Gt); (2) Level 1 product accuracy with terrain correction and ground control (L1T); (3) band-to-band registration accuracy; and (4) multi-temporal image-to-image registration accuracy. Using the results of the on-orbit calibration update, all aspects of geometric performance were shown to meet or exceed system requirements.

On-orbit geometric calibration is a key technology to guarantee the geometric quality of high-resolution optical satellite imagery. In this paper, we present an approach for the on-orbit geometric calibration of high-resolution optical satellite imagery, focusing on two core problems: constructing an on-orbit geometric calibration model and proposing a robust calculation method. First, a rigorous geometric imaging model is constructed based on the analysis of the major error sources. Second, we construct an on-orbit geometric calibration model through performing reasonable optimizing and parameter selection of the rigorous geometric imaging model. On this basis, the calibration parameters are partially calculated with a stepwise iterative method by dividing them into two groups: external and internal calibration parameters. Furthermore, to verify the effectiveness of the proposed calibration model and methodology, on-orbit geometric calibration experiments for ZY1-02C panchromatic camera and ZY-3 three-line array camera are conducted using the reference data of the Songshan calibration test site located in the Henan Province, China. The experimental results demonstrate a certain deviation of the on-orbit calibration result from the initial design values of the calibration parameters. Therefore, on-orbit geometric calibration is necessary for optical satellite imagery. On the other hand, by choosing multiple images, which cover different areas and are acquired at different points in time to verify their geometric accuracy before and after calibration, we find that after on-orbit geometric calibration, the geometric accuracy of these images without ground control points is significantly improved. Additionally, due to the effective elimination of the internal distortion of the camera, greater geometric accuracy was achieved with less ground control points than before calibration.

During machining operations on machining centres, there are a large number of internal and external factors that act on the technological system. They generate errors that influence the manufacturing cost, productivity, and machining accuracy. The monitoring and control system developed for machining centres presented in this paper consists of 3D touch probes, a device for registering a contact between the cutting tool and workpiece, devices for measuring the geometric accuracy of the machine tool and for calibrating the touch probe in the spindle, parameterised CNC programmes, computer and software for data processing and database management. The developed system guarantees monitoring of the machining accuracy, low cost, high level of productivity, low number of preparatory work and measurements, increased reliability due to reduced scrap rate by reducing the probability of cutting tool breakage, the possibility of automating the measurements and processing the data, and wide applicability.

Purpose This paper aims to provide an experimental evaluation of geometric errors on the edges of parts manufactured by the fused deposition modeling (FDM) process. Design/methodology/approach An experimental plan was conducted by building parts in ABS thermoplastic resin on a commercially available machine with given combinations of the three geometric variables (inclination, included and incidence angle) defined in the first part of the paper. Edges on built parts were inspected on a two-dimensional non-contact profilometer to measure position and form errors. Findings The analysis of measurement results revealed that the edge-related variables have significant influences on the geometric errors. The interpretation of error variations with respect to the different angles confirmed the actual occurrence of the previously discussed error causes. As an additional result, quantitative predictions of the errors were provided as a function of angle values. Research limitations/implications The experimental results refer to fixed process settings (material, FDM machine, layer thickness, build parameters, scan strategies). Originality/value The two-part paper is apparently the first to have studied the edges of additively manufactured parts with respect to geometric accuracy, a widely studied topic for surface features.

A special acrylic phantom designed for both magnetic resonance imaging (MRI) and computed tomography (CT) was used to assess the geometric accuracy of MRI-based stereotactic localization with the Leksell stereotactic head frame and localizer system. The acrylic phantom was constructed in the shape of a cube, 164 mm in each dimension, with three perpendicular arrays of solid acrylic rods, 5 mm in diameter and spaced 30 mm apart within the phantom. Images from two MR scanners and a CT scanner were obtained with the same Leksell head frame placement. Using image fusion provided by the Leksell GammaPlan (LGP) software, the coordinates of the intraphantom rod positions from two MRI scanners were compared to that of CT imaging. The geometric accuracy of MR images from the Siemens scanner was greatly improved after the implementation of a special software patch provided by the manufacturer. In general, much better accuracy was achieved in the transverse plane where images were acquired. Most distortion was found around the periphery while least distortion was present in the middle and most other parts of the phantom. For most intracranial lesions undergoing stereotactic radiosurgery, accuracy of target localization can be achieved within size of a voxel, especially with the Siemens scanner. However, extra caution should be taken for imaging of peripheral lesions where the distortion is the greatest. 2001 American College of Medical Physics.

The Institute of Optical Sensor Systems (OS) as member of the Robotics and Mechatronics Cluster of the German Aerospace Center (DLR) has more than 30 years experiences with high-resolution imaging technology. The technology changes in the development of detectors, as well as the significant change of the manufacturing accuracy in combination with the engineering research define the next generation of spaceborne sensor systems focusing on Earth observation and remote sensing. The combination of large TDI (time delay and integration) lines, intelligent synchronization control, fast-readable sensors and new focal-plane concepts open the door to new remote-sensing instruments. This class of instruments is feasible for high-resolution sensor systems regarding geometry and radiometry and their data products like 3D virtual reality. Systemic approaches are essential for such designs of complex sensor systems for dedicated tasks. The system theory of the instrument inside a simulated environment is the beginning of the optimization process for the optical, mechanical and electrical designs. Single modules and the entire system have to be calibrated and verified. Suitable procedures must be defined on component, module and system level for the assembly test and verification process. This kind of development strategy allows the hardware-in-the-loop design. The paper gives an overview about the current developments at DLR OS in the field of innovative sensor systems design for spatial and spectral high resolution remote sensing instruments.

WOS: 000315154800052, Advancements in the geometric resolution of space images have improved the conditions for generations of large-scale topographic maps. Using WorldView-1, WorldView-2, and GeoEye-1, images can now be captured from space with a 0.5 m ground sampling distance (GSD). Geometric accuracy and information content are the most significant components of mapping from space images. Depending on the resolution, image quality, and shadows, the identification and classification of ground objects may prove challenging. In this research, the geometric accuracy and information content, of panchromatic WorldView-1 images, were analyzed by covering parts of Istanbul and Zonguldak in Turkey. Each of these locations has various topographic characteristics. For the orientation and investigation of the geometric accuracies of images, a number of ground control points (GCPs) were developed as independent checkpoints. Based on bias-corrected rational polynomial coefficients with one GCP, a standard deviation of independent checkpoints on the range of one GSD was obtained. The information content of images was analyzed by mapping all buildings, in both test areas, and comparing the results with reference 1/5000 scaled topographic maps. The results verified that the WorldView-1 images can be utilized for generating and updating 1/5000 scaled topographic maps of urban areas. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.52.2.026201]

This paper deals with the control parameters for selected geometric accuracy measurements for a machine tool. The parameters were needed after a refurbished milling machine was purchased. After setting up the machine, it was necessary to check the geometric accuracy that can be used for precise milling. The whole check was performed in accordance with ISO 10791. Only selected parameters of geometric accuracy were inspected, and they were later compared with the prescribed values. On the basis of a comparison of these values we were able to determine whether the machine tool can be used for accurate machining.

The department of Optical Information Systems (OS) at the Institute of Robotics and Mechatronics of the German Aerospace Center (DLR) has more than 25 years experience with high-resolution imaging technology. The technology changes in the development of detectors, as well as the significant change of the manufacturing accuracy in combination with the engineering research define the next generation of spaceborne sensor systems focusing on Earth observation and remote sensing. The combination of large TDI lines, intelligent synchronization control, fast-readable sensors and new focal-plane concepts open the door to new remote-sensing instruments. This class of instruments is feasible for high-resolution sensor systems regarding geometry and radiometry and their data products like 3D virtual reality. Systemic approaches are essential for such designs of complex sensor systems for dedicated tasks. The system theory of the instrument inside a simulated environment is the beginning of the optimization process for the optical, mechanical and electrical designs. Single modules and the entire system have to be calibrated and verified. Suitable procedures must be defined on component, module and system level for the assembly test and verification process. This kind of development strategy allows the hardware-in-the-loop design. The paper gives an overview about the current activities at DLR in the field of innovative sensor systems for photogrammetric and remote sensing purposes.

INTRODUCTION: The aims of this study were to determine the linear accuracy of 3-dimensional surface models derived from a commercially available cone-beam computed tomography (CBCT) dental imaging system and volumetric rendering software and to investigate the influence of voxel resolution on the linear accuracy of CBCT surface models.METHODS: Glass sphere markers were fixed on 10 dry mandibles. The mandibles were scanned with 0.40 and 0.25 voxel size resolutions in 3 sessions. Anatomic truth was established with 6 direct digital caliper measurements. The surface models were rendered by a volumetric rendering program, and the CBCT measurements were established as the mean of the 3 measurements.RESULTS: The intraclass correlation coefficients between the physical measurements and the measurements of the CBCT images of 0.40 and 0.25 voxels were all more than 0.99. All CBCT measurements were accurate. There was no difference between the accuracy of the measurements between the 0.40 and 0.25 voxel size groups. The smallest detectable differences of the CBCT measurements were minimal, confirming the accuracy of the CBCT measurement procedure.CONCLUSIONS: The measurements on 3-dimensional surface models of 0.25 and 0.40 voxel size data sets made with the 3D eXam CBCT scanner (KaVo Dental GmbH, Bismarckring, Germany) and SimPlant Ortho Pro software (version 2.00, Materialise Dental, Leuven, Belgium) are accurate compared with direct caliper measurements. An increased voxel resolution did not result in greater accuracy of the surface model measurments.

Summary Purpose A proper control of the geometrical accuracy of treated portals during radiotherapy results in higher quality of treatment and may lead to the increase in the therapeutic gain. In this work, an evaluation of an electronic portal imaging device (EPID) was made in the following aspects: the quality of images, the estimation of prolongation of the treatment, and the corrections introduced after EPIDs. Material and methods We have archived 2430 portal images of 184 patients who were irradiated at our department. The following significant errors were established: a shift in the field along x, y, z axes (more than 5 mm in the head and neck region, more than 7 mm in the chest tumours and 10 mm in pelvic region), a displacement of shield by the same values, and an erroneous field size assigment by more than 10 mm. Results The introduction of the EPID into clinical practice involved approximately 10% of the session time. The quality of the electronic portal images received was acceptable for further analysis in 87% of the analysed group of patients. Significant errors have been registered in 33% of monitored patients. Prior to the treatment and during the set-up procedure, corrections were made in 20% of the evaluated patients. Conclusions An electronic portal imaging device (EPID) is a useful tool for fast and reliable portal image acquisition.

Incremental sheet forming (ISF) has gained much attention in the low volume production and rapid prototyping fields due to its inherent flexibility, low-overhead cost, and die-less nature. However, the geometric inaccuracy of the final achievable parts hinders this process from becoming commercially viable. One of the major sources of geometric inaccuracy is springback, which predominately occurs when the formed sheet metal is unloaded by the forming tools and released from the clamps. This paper focuses on the latter case. A practical annealing method that does not rely on complicated setups and geometry-specific compensation algorithms is proposed to reduce the springback that occurs after the unclamping process. Two clamping devices were developed, which have been demonstrated to significantly reduce the amount of springback. The capability of reducing springback by the proposed method and its potential of integrating it with other geometric accuracy improvement methods will enhance the ISF process towards future industrial applications.