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The aim of this paper is to share our experiences and thoughts about a project course in geoinformatics. The course has been organised annually since 2017. We hope that this article provides ideas about when new project-based courses are designed or existing ones are renewed. We wanted to increase students’ motivation by providing assignments from companies or other organisations as well as cooperation with them. Working with real clients makes the project work much more interesting than projects without a real-life connection. We provide topics from various fields of geoinformatics, such as geoinformation technology, geodesy, photogrammetry, laser scanning and remote sensing. The students worked in small groups that were supported by an advisor and a facilitator. The advisor helps with substance and the facilitator assists with reflection and improving working process, i.e. not only to complete the task but also to learn about capabilities for project work, self-directive teamwork and learning to learn (meta learning). To sum up, during the course students increase their knowledge and expertise on geoinformatics, learn skills for client-centered project work and learn how to support their learning through self- and peer-reflection. In other words, the course aims to develop skills that are useful throughout the students’ forthcoming careers.

By combining game engines with indoor mapping, it is possible to create interactive virtual environments that represent the real world. In this paper a virtual version of an audio installation in a historic building is produced, where the user freely explores the building and experiences a set of audio clips, creating a virtual radio play. A depth camera indoor mapping system, Matterport, captured a set of staged interiors. The aim was to evaluate the quality and usability of the indoor models and to demonstrate applying them in 3D application development. The quality of the models was evaluated by comparison with laser scanning, revealing limitations with Matterport: increasing the size of the measured area lowered the level of detail and accuracy of volumetric models. The quality of textures was not affected by this limitation, maintaining the appearance of models. To obtain optimised models for mobile 3D applications, a manual revision process was applied.

Integration of laser scanning data and photographs is an excellent combination regarding both redundancy and complementary. Applications of integration vary from sensor and data calibration to advanced classification and scene understanding. In this research, only airborne laser scanning and aerial images are considered. Currently, the initial registration is solved using direct orientation sensors GPS and inertial measurements. However, the accuracy is not usually sufficient for reliable integration of data sets, and thus the initial registration needs to be improved. A registration of data from different sources requires searching and measuring of accurate tie features. Usually, points, lines or planes are preferred as tie features. Therefore, the majority of resent methods rely highly on artificial objects, such as buildings, targets or road paintings. However, in many areas no such objects are available. For example in forestry areas, it would be advantageous to be able to improve registration between laser data and images without making additional ground measurements. Therefore, there is a need to solve registration using only natural features, such as vegetation and ground surfaces. Using vegetation as tie features is challenging, because the shape and even location of vegetation can change because of wind, for example. The aim of this article was to compare registration accuracies derived by using either artificial or natural tie features. The test area included urban objects as well as trees and other vegetation. In this area, two registrations were performed, firstly, using mainly built objects and, secondly, using only vegetation and ground surface. The registrations were solved applying the interactive orientation method. As a result, using artificial tie features leaded to a successful registration in all directions of the coordinate system axes. In the case of using natural tie features, however, the detection of correct heights was difficult causing also some tilt errors. The planimetric registration was accurate.

The paper presents a novel method to measure 3-D deformation of a large metallic frame structure of a crane under loading from one to several images, when the cameras need to be attached to the self deforming body, the structure sways during loading, and the imaging geometry is not optimal due to physical limitations. The solution is based on modeling the deformation with adequate shape functions and taking into account that the cameras move depending on the frame deformation. It is shown that the deformation can be estimated even from a single image of targeted points if the 3-D coordinates of the points are known or have been measured before loading using multiple cameras or some other measuring technique. The precision of the method is evaluated to be 1 mm at best, corresponding to 1:11400 of the average distance to the target.

The paper deals with estimation of 3-D object deformation from multiple images initially in fixed positions with weak or strong imaging geometry. A new method is proposed to detect automatically if the exterior or interior orientations (rotations, translations, focal length, principal point) of one or several images have changed and which image or images contain the error, when the object deforms at the same time. The method is based on comparing novel feature vectors computed for each image from changes in the image coordinates of the object points and from residuals derived from the collinearity equations. Bundle adjustment is performed to simultaneously estimate the deformation of the object and to correct the changed orientations of the images. The rigidity needed in the weak case is obtained by approximating the deformation by a novel shape function containing parameters the values of which are estimated during adjustment. Test results with synthetic data show that even rather small changes in one orientation parameter of one image can be detected with high confidence. Weak imaging geometry allows to detect smaller changes than the strong one. The closer an initial approximation of deformation is available, the higher is the probability of correct detection. Subsequent correction of changed orientations and estimation of deformation may provide a high accuracy of 1:140000 of the object dimensions for both weak and strong imaging geometries, when the noise level in the image measurements is 0.1 pixel. Experiments with real data illustrate the good performance of the methods.

In this paper, terrestrial laser scanning (TLS), photogrammetric and total station measurements were compared with dial gauge observations in two different loading experiments on a reinforced concrete beam. In the first test, the T-beam was stressed in several loading phases resulting in deformations of up to 13·63 mm. All measuring methods were able to detect deformations with an accuracy of better than 0·38 mm. The theoretical calculations of deflections based on a form of Euler–Bernoulli beam equation, however, underestimated the maximum bending of 4·08 mm. A similar loading experiment was applied on a rectangular concrete beam. In this case, the maximum deformation of the beam was 14·94 mm and measuring accuracies of all methods were better than 0·44 mm. The accuracy of theoretical calculations was better than 2·07 mm. The results indicate that laser scanning could be used as an alternative or complementary method to photogrammetric and total station measurements for detecting structural deformations in buildings. Resume Dans cet article, des mesures utilisant le laser terrestre a balayage, la photogrammetrie et la station totale ont ete confrontees a celles d’un comparateur a cadran dans deux experiences de charge d’une poutre en beton renforce. Dans le premier test, la poutre en T a subi plusieurs phases de charge qui ont engendre des deformations atteignant 13,63 mm. Toutes les methodes de mesure ont pu detecter les deformations avec une precision meilleure que 0,38 mm. Les calculs theoriques de la fleche bases sur l’equation des poutres d’Euler–Bernoulli ont neanmoins sous-estime la flexion maximale de 4,08 mm. Une experience similaire a ete menee sur une poutre en beton rectangulaire. Dans ce cas, la deformation de la poutre etait de 14,94 mm et les precisions de mesure de toutes les methodes etaient meilleures que 0,44 mm. La precision des calculs theoriques etait meilleure que 2,07 mm. Les resultats montrent que le laser a balayage pourrait etre utilise en substitution ou en complement a la photogrammetrie et a la station totale pour la detection de deformations structurales dans des bâtiments. Zusammenfassung Dieser Beitrag vergleicht terrestrisches Laserscanning (TLS) und Messungen mit einer Totalstation mit Messuhr-Beobachtungen zweier Belastungsexperimente eines armierten Betontragers. In einem ersten Test wurde ein T-Trager verschiedenen Belastungsphasen mit Deformationen von bis zu 13·63 mm ausgesetzt. Alle Messmethoden konnten die Deformationen mit einer Genauigkeit von unter 0·38 mm erfassen. Die theoretischen Berechnungen der Durchbiegung auf der Basis einer Form der Euler–Bernoulli Tragergleichung unterschatzte jedoch die maximale Biegung von 4·08 mm. Ein ahnliches Belastungsexperiment wurde fur einen rechteckigen Betontrager durchgefuhrt. In diesem Fall lag die maximale Deformation des Tragers bei 14·94 mm und die Messgenauigkeit aller Methoden war besser als 0·44 mm. Die Genauigkeit der theoretischen Berechnungen lag unter 2·07 mm. Die Ergebnisse weisen darauf hin, dass zur Bestimmung von strukturellen Deformationen von Gebauden Laserscanning als Alternative oder Erganzung zu photogrammetrischen Messungen oder zu Messungen mit einer Totalstation betrachtet werden kann. Resumen En este articulo se comparan las observaciones obtenidas mediante un dispositivo calibrador con las obtenidas con un escaner laser terrestre, mediante fotogrametria y con una estacion total, en dos experimentos de carga sobre una viga de hormigon reforzado. En el primer ensayo, la viga en T se sometio a varias fases de carga que dieron lugar a deformaciones de hasta 13,63 mm. Todos los metodos de medida permitieron detectar deformaciones con una exactitud superior a 0,38 mm. Los calculos teoricos de las flexiones, basados en una forma de la ecuacion de Euler–Bernoulli, subestimaron sin embargo la curvatura maxima de 4,08 mm. Se realizo un experimento similar de carga sobre una viga de hormigon rectangular y en este caso la deformacion maxima de la viga fue de 14,94 mm y las exactitudes medidas con todos los metodos fueron superiores a 0,44 mm. La exactitud de los calculos teoricos supero los 2,07 mm. Los resultados indican que el escaner laser puede utilizarse como metodo alternativo o complementario a las medidas fotogrametricas y con estacion total para detectar las deformaciones estructurales en los edificios.

Techniques based on laser point clouds and digital terrestrial images were demonstrated for the calibration of tree-height estimation. Individual tree heights can be roughly estimated from laser scanning data by using the approximated ground level and the highest hit of the treetop. However, laser-derived measurements often underestimate tree heights. This underestimation can arise from various error sources. Digital terrestrial images can be used to verify and understand the behaviour of laser point clouds. When laser data are backprojected in a close-range image, it is possible to show where each laser beam has reflected. This, however, requires a proper orientation of the images. In this study an interactive orientation method was used to derive image orientations, using one laser strip at a time as the reference data. Consequently, the backprojection of laser point clouds confirmed the height underestimations found by comparing the tacheometer reference measurements with the laser-derived tree heights...

The paper deals with the registration and modeling of multiple 3-D profile maps acquired from different viewpoints by light striping. We analyze the propagation of measurement and calibration errors to the registration parameters and further to the reconstructed model of the scene consisting of planar patches. The analysis is performed for two strategies. In the first strategy, the maps are registered simultaneously using the Levenberg–Marquardt method to update the registration parameters and the model computed afterwards while in the second one, the maps are registered sequentially against the model reconstructed up till then using the method of unit quaternions to update the registration parameters. Our statistical analysis thus combines the registration and modeling steps, and in registration, we determine the corresponding points either on the parametric domains of the maps or as closest points in 3-D using the information from the parametric domain to restrict the search for the closest points. We also point out the precise estimation of the covariance matrix of the solution given by the Levenberg–Marquardt method. We illustrate the results of our analysis with real data from a scale model of an urban area.

Measurement of dimensions of inaccessible objects remains a challenge in spite of new technologies available. The authors of this article approached the problem with a photogrammetric method using a laser-camera combination installed in a helicopter. The method was applied to the topographic measurement of ice fields.

Recently, research towards using 3D city models for personal navigation has been rapidly increasing. In this paper, an approach for 3D city model reconstruction for the application of mobile phone-based navigation is presented, which is based on data collected from vehicle-based mobile mapping system (MMS). Our method is performed based on three objectives: small model size, perfect accuracy control as well as good visual effect. Small model size is achieved by simplified object geometry and reduced texture resolution. Model accuracy is controlled by extracting building outlines from classified point cloud and overlapping with final 3D model. Model completeness is checked by comparing resulting model with original images. Good visual effect is realized by applying photo-realistic texture. Photorealistic texture provides rich information for the reconstructed 3D scene. By applying this approach, in test area, 3D city model is successfully reconstructed.

Spherical images are linear images, which are exact in central projection. They are explicitly determined by the projection centre. The technical approach consists of collecting scenery through a single perspective and combining the images like panoramic mosaics. A general application of spherical imaging is hempispehric visualisation of space. In hemispheric visualisation, we distinguish between horizontal, half hemispheric, and full hemispheric imaging. The photogrammetric applications of spherical imaging aim at acquisition of 3D environmental or terrain models. Then the base to distance ratio is typically large. We assume, that the primary advantage of spherical imaging will be nevertheless on stereoscopy applications. We aim at full-scale stereoscopy with projection of spherical images in scale of 1:1. In case of full-scale stereoscopy, the stereoscopic plasticity will have a value of 1 and the base is typically short. Natural viewing would equal to base lengths of human eyes, i.e. to 65 mm. We present in the paper the Stereodrome, which is a physical realisation of full-scale stereo viewing. It consists of a photogrammetric workstation, a high-resolution stereo projector, necessary stereo eye-ware, and a back projection screen. Originally we have motivated us for building the Stereodrome by the fact that it is the only means to really see the behaviour of 3D point clouds in details. In the paper we will also discuss, in which way full-scale stereo display has been used for validating the quality of existing 3D geoinformation.

This paper evaluates and discuses the accuracy of laser scanner in DTM (digital terrain model) generation in forested and suburban areas. Special emphasis is laid in order to optimize the selection of ground hits used for the creation of the DTM of future high-pulse-rate laser scanners. A novel DTM algorithm is depicted in detail. The algorithm is based on five phases: (1) calculation of the original reference surface, (2) classification of vegetation and removal of the vegetation from the reference surface, (3) classification of the original cloud of points using the reference surface, (4) calculation of the DTM based on the classified ground hits, and (5) interpolation of the missing points. Standard error of 15 cm was obtained for flat forest areas and the error increased with increasing terrain slope to the value of approximately 40 cm at the slope of 40%. The average standard error for forest area was slightly better than 25 cm. The laser-derived DTM of the forest road deviated only 8.5 cm from the true height. An optimum performance for the DTM generation was obtained by averaging the ground hits which located, at the maximum, 60 cm above the minimum terrain values. A simplified algorithm was suggested for more operational use based on the first pulse mode data. Special cases of the suburban area DTM were verified including terrain heights below the buildings and bridges, terrain heights of roads, terrain heights below large outdoor light fixture, to name but a few. About 100 special cases in suburban/urban environment for DTM verification were searched. The corresponding standard error between the laser-derived values and reference data was 45 cm.

The paper deals with concentric image capturing and its use for mapping and visualization purposes. The work is based on a photogrammetric approach in composing hemispheric images from concentric image sequences.

The paper deals with our research on developing videogrammetry based 3D modeling procedure for indoor facilities. The modeling is based on recorded video sequences, and the analysis procedure is reverse if compared to the traditional one. Here a functional 3D model is built first and the measurements for exact geometry are done thereafter: `Modeling first--then measuring'. The final output will be a photorealistic model.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The application of video imagery for photogrammetric tasks may be divided according to the task into on-line or off-line use. In Finland, the first successful on-line systems were installed for the position measuring of car bodies in Spring 1992. The on-line applications have grown interest within industrial production because they are operative and a payback period is thus countable. As it regards the off-line use, the situation is different and the efficiency in 3D data acquisition seems to play the decisive role. In the paper the different characteristics in performing the on-line and off-line videogrammetry are presented. The 3D measurements are exemplified with the applications. These cover both existing references in industrial `on-line' applications and ongoing development of `off-line' 3D object digitizing procedures.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Within industrial off-line applications the complete 3-D digitizing of object surfaces willbe performed using stereo videography. Typical examples where the off-line measure-ments are needed, are: 1) the reverse engineering during the industrial design; and 2)the quality control during the process setup. In both cases the measuring tasks areless time constrained than in the case of the on-line control. On the contrary, therequirements are higher as it regards the completeness of the recovered object modeland the accuracy of the object measures.Within the paper an off-line 3-D measuring procedure is discussed. The procedure isunder development in a project which belongs to the national research programme onmachine vision in Finland 1992-1996. The procedure consists of four concurrentphases: 1) recording, 2) rectification, 3) digitizing, and 4) modelling. The recordingsare based on sequential stereo videography and the continuous object digitizing isbased on the rigid normal case of stereography. The system modules are: 1) the two

A photogrammetric station is a configuration of several video cameras which are used for automated 3D measuring of industrial objects. All measurements are performed from the image observations only, and the targets are natural features or projected light patterns. The first `on-line' applications are for car body orientation within a robotic sealing cell and for 3D verification of ship screws within a robotic machining step. The `off-line' applications are for object reconstructions for reverse engineering purposes.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Automated photogrammetric vision systems, called photogrammetric stations, are used for industrial on-line control. The stations are on-site calibrated camera setups with necessary image processing in order to provide the manufacturing process with three-dimensional control data. One of the first operative industrial applications is the car body orientation within a seam sealing cell in automotive manufacturing.

Some principles of using template images for close-range photogram- metric coordinate determination are described. The primary use is the automatic stability control of the photogrammetric stations. In the case of applications, such as within manufacturing process cont- rol, the template images substitute the need of manual targetting.

A photogrammetric machine vision system, called Mapvision, has been developed at the Technical Research Centre of Finland. The paper deals with the principles of real-time photogrammetry as applied to machine vision. There is a brief overview of the present machine vision markets and the commercial systems available. The practical examples presented concern the tentative experiences in applying the Mapvision and its preceding prototype system for industrial inspection and assembly control.

Photogrammetry is the art, science and technology of obtaining reliable three-dimensional information about physical objects and the environment through processes of recording, measuring, and interpreting photographic images and patterns of electromagnetic radiant energy and other phenomena. In real-time photogrammetry, and specifically when applied to machine vision, the solid state video cameras act as dynamic two-dimensional records of scences containing all the actual information for continuous gathering of three-dimensional object space data. Both passive and active real-time photogrammetric systems are discussed.

A real-time photogrammetric system has been developed at the Technical Research Centre of Finland. The system consists of solid-state video cameras and a photogrammetric microprocessor. The processor is especially programmed for image processing and for photogrammetric operations. The system concept is versatile in regard to the measuring requirements: first, the cameras may be freely oriented in relation to the object; secondly, the use of video allows the utilization of different kind of imagery in respect of the spectral response; and thirdly, the spatial measuring accuracy may be adjusted according to the purpose. The first tentative applications of this non-contact and three-dimensional machine vision technique have been within the fields of surveillance and industrial quality assurance.

Mapvision is a photogrammetric machine vision system developed by the Technical Research Centre of Finland primarily for industrial inspection and assembly control applications. The system consists of four simultaneously operating solid state cameras and an especially programmed photogrammetric microprocessor. The three-dimensional measuring accuracy is better than 1:5,000. The Mapvision is an automated system enabling for example the dimensional feed-back and interaction between computer aided design and manufacturing phases.