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This paper presents the development of a low cost UAV (Unmanned Aerial Vehicle) with the capability of direct georeferencing. The advantage of such system lies in its high maneuverability, operation flexibility as well as capability to acquire image data without the need of establishing ground control points (GCPs). Moreover, the precise georeferencing offers an improvement in the final mapping accuracy when employing integrated sensor orientation. Such mode of operation limits the number and distribution of GCPs, which in turns save time in their signalization and surveying. Although the UAV systems feature high flexibility and capability of flying into areas that are inhospitable or inaccessible to humans, the lack of precision in positioning and attitude estimation on-board decrease the gained value of the captured imagery and limits their mode of operation to specific configurations and need of groundreference. Within a scope of this study we show the potential of present technologies in the field of position and orientation determination on a small UAV. The hardware implementation and especially the non-trivial synchronization of all components is clarified. Thanks to the implementation of a multi-frequency, low power GNSS receiver and its coupling with redundant MEMSIMU, we can attain the characteristic of a much larger systems flown on large carries while keeping the sensor size and weight suitable for MAV operations.

The main purpose of any aerial photo archive is to allow quick access to images based on content and location. Therefore, next to a description of technical parameters and depicted content, georeferencing of every image is of vital importance. This can be done either by identifying the main photographed object (georeferencing of the image content) or by mapping the center point and/or the outline of the image footprint. The paper proposes a new image archiving workflow. The new pipeline is based on the parameters that are logged by a commercial, but cost-effective GNSS/IMU solution and processed with in-house-developed software. Together, these components allow one to automatically geolocate and rectify the (oblique) aerial images (by a simple planar rectification using the exterior orientation parameters) and to retrieve their footprints with reasonable accuracy, which is automatically stored as a vector file. The data of three test flights were used to determine the accuracy of the device, which turned out to be better than 1° for roll and pitch (mean between 0.0 and 0.21 with a standard deviation of 0.17–0.46) and better than 2.5° for yaw angles (mean between 0.0 and −0.14 with a standard deviation of 0.58–0.94). This turned out to be sufficient to enable a fast and almost automatic GIS-based archiving of all of the imagery.

The direct georeferencing in aerial photogrammetry requires precise measurement of position and attitude of an image sensor, because the object point position is computed directly using this data. But for several reasons, data from onboard inertial navigation system can not be used for this purpose directly. Especially GNSS antenna displacement and image sensor misalignment have to be compensated and different rotation and coordinate system conventions have to be taken into account. This paper describes the transformations of onboard GNSS/INS data for the needs of the direct georeferencing and demonstrates it on a real UAV photogrammetric mission.

UAV systems have become an attractive data acquisition platform in emerging applications. As measuring instrument they extend the lineup of possible surveying methods in the field of geomatics. However, most of UAVs are equipped with low-cost navigation sensors such as GPS or INS, allowing a positioning accuracy of 3 to 5 m. As a result the acquired position- and orientation data fea- tures a low accuracy which implicates that it cannot be used in applications that require high precision data on cm-level (e.g. direct georeferencing). In this paper we will analyze the potential of differential post-processing of GPS data from UAV in order to im- prove the positioning accuracy for applications basing on direct georeferencing. Subsequently, the obtained results are compared and verified with a track of the octocopter carried out with a total station simultaneously to the GPS data acquisition. The results show that the differential post-processing essentially improved the accuracy of the Falcon position data. Thereby the average offset be- tween the data sets (GPS data, track) and the corresponding standard deviation is 0.82 m and 0.45 m, respectively. However, under ideal conditions it is even possible to improve this positioning accuracy to the cm-range. Furthermore, there are still several sources of error such as the offset between the GPS antenna of the Falcon 8 and the prism which is used for the track. Considering this fact there is further room for improvement regarding the here discussed positioning method., International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, XXXVIII-1/C22, ISSN:1682-1750, ISSN:2194-9034, ISSN:1682-1777, Proceedings of the International Conference on Unmanned Aerial Vehicle in Geomatics (UAV-g)

To facilitate applications such as environment detection or disaster monitoring, the development of rapid low cost systems for collecting near real time spatial information is very critical. Rapid spatial information collection has become an emerging trend for remote sensing and mapping applications. In this study, a fixed-wing Unmanned Aerial Vehicle (UAV)-based spatial information acquisition platform that can operate in Ground Control Point (GCP) free environments is developed and evaluated. The proposed UAV based photogrammetric platform has a Direct Georeferencing (DG) module that includes a low cost Micro Electro Mechanical Systems (MEMS) Inertial Navigation System (INS)/ Global Positioning System (GPS) integrated system. The DG module is able to provide GPS single frequency carrier phase measurements for differential processing to obtain sufficient positioning accuracy. All necessary calibration procedures are implemented. Ultimately, a flight test is performed to verify the positioning accuracy in DG mode without using GCPs. The preliminary results of positioning accuracy in DG mode illustrate that horizontal positioning accuracies in the x and y axes are around 5 m at 300 m flight height above the ground. The positioning accuracy of the z axis is below 10 m. Therefore, the proposed platform is relatively safe and inexpensive for collecting critical spatial information for urgent response such as disaster relief and assessment applications where GCPs are not available.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:44:37Z No. of bitstreams: 1 S1982-21702011000300001.pdf: 513387 bytes, checksum: 74678beb1aee76072e728a777908dd6b (MD5) Made available in DSpace on 2013-08-22T18:44:37Z (GMT). No. of bitstreams: 1 S1982-21702011000300001.pdf: 513387 bytes, checksum: 74678beb1aee76072e728a777908dd6b (MD5) Previous issue date: 2011-09-01 Made available in DSpace on 2013-09-30T19:32:59Z (GMT). No. of bitstreams: 2 S1982-21702011000300001.pdf: 513387 bytes, checksum: 74678beb1aee76072e728a777908dd6b (MD5) S1982-21702011000300001.pdf.txt: 52166 bytes, checksum: f395eda1de282fae0735ab426aff6793 (MD5) Previous issue date: 2011-09-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:09:01Z No. of bitstreams: 2 S1982-21702011000300001.pdf: 513387 bytes, checksum: 74678beb1aee76072e728a777908dd6b (MD5) S1982-21702011000300001.pdf.txt: 52166 bytes, checksum: f395eda1de282fae0735ab426aff6793 (MD5) Made available in DSpace on 2014-05-20T15:09:01Z (GMT). No. of bitstreams: 2 S1982-21702011000300001.pdf: 513387 bytes, checksum: 74678beb1aee76072e728a777908dd6b (MD5) S1982-21702011000300001.pdf.txt: 52166 bytes, checksum: f395eda1de282fae0735ab426aff6793 (MD5) Previous issue date: 2011-09-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Sensores de posição e orientação podem ser adquiridos e integrados com um custo relativamente baixo para aplicações em mapeamento. A utilização de câmaras digitais de pequeno e médio formato em sistemas de aquisição de imagens aéreas, proporciona vantagens sobre sistemas fotogramétricos convencionais, como: redução de custo, dimensões e peso. Este trabalho teve como objetivo a implementação e avaliação de hardware e software para permitir o sincronismo entre receptores GPS e câmaras digitais de modo a fornecer diretamente as coordenadas do centro perspectivo. O sincronismo foi realizado com o uso do sistema operacional Linux, juntamente com o software NTP, responsável por sincronizar o relógio do computador com uma referência de tempo externa. A validação foi realizada comparando-se diretamente os instantes registrados pelo sistema comercial SPAN-CPT e a técnica proposta neste trabalho. Além disto, os Centros Perspectivos (CPs) determinados pelas técnicas implementadas foram usados em experimentos com fototriangulação de um bloco de imagens, possibilitando a análise de discrepâncias nos pontos de verificação. O resultado do sincronismo apresentou discrepâncias da ordem de 0,15 m em relação ao sistema comercial, implicando na determinação das coordenadas dos CPs com qualidade compatível com a aplicação da técnica desenvolvida em projetos de mapeamento. Currently, position and orientation sensors can be acquired and integrated with affordable costs for mapping applications. In this context, small and medium format digital cameras can be included as a part of aerial image acquisition system with advantages when compared to conventional photogrammetric systems, due to its low cost, size, weight and handling ease. This work aims at the implementation and experimental assessment of hardware and software components for synchronization of a GPS receiver and a digital camera to directly measure and provide the perspective center coordinates. Synchronization was based on Linux operational system, and NTP software, used to synchronize computer time with an external reference time. The validation of the implemented system was perfomed by comparing directly the events recorded in a commercial navigation system (SPAN-CPT) and from the proposed technique. Furthermore, the PC coordinates determined by these techniques were used in an aerial triangulation, enabling the analysis of discrepancies in the checkpoints. The result of the synchronization showed discrepancies rounding 0.15 m with respect to the commercial system, resulting in the determination of the PC coordinates with quality compatible with its application in mapping projects. Unesp Faculdade de Ciências e Tecnologia Unesp Faculdade de Ciências e Tecnologia

A land-based mobile mapping system (MMS) is flexible and useful for the acquisition of road environment geospatial information. It integrates a set of imaging sensors and a position and orientation system (POS). The positioning quality of such systems is highly dependent on the accuracy of the utilized POS. This limitation is the major drawback due to the elevated cost associated with high-end GPS/INS units, particularly the inertial system. The potential accuracy of the direct sensor orientation depends on the architecture and quality of the GPS/INS integration process as well as the validity of the system calibration (i.e., calibration of the individual sensors as well as the system mounting parameters). In this paper, a novel single-step procedure using integrated sensor orientation with relative orientation constraint for the estimation of the mounting parameters is introduced. A comparative analysis between the proposed single-step and the traditional two-step procedure is carried out. Moreover, the estimated mounting parameters using the different methods are used in a direct geo-referencing procedure to evaluate their performance and the feasibility of the implemented system. Experimental results show that the proposed system using single-step system calibration method can achieve high 3D positioning accuracy.

Since about 10 years, airborne laser scanning (ALS) entered as a classical way of acquiring 3D data of our environment. This paper presents the theoretical aspects of this mapping technique through the components (LiDAR, scanning devices, and direct georeferencing sensors) and its error sources. The performance of such system, such as the mapping accuracy or the data density, is treated. The huge amount of data generated by ALS technique requires a specific post-processing to provide usable dataset for the users. The acquisition and processing phases, from trajectory processing to final product, are described. Finally, few practical experiences of oblique data acquired with a helicopter-based LiDAR system in mountain areas, illustrate the potential of this mapping technique., Depuis une dizaine d'années, la lasergrammétrie ou LiDAR aéroporté est une technique reconnue et quasi classique pour détermi¬ ner la topographie de notre environnement. L 'article suivant aborde d 'abord les aspects théoriques de cette technique au travers de ses composants (LiDAR, techniques de balayage, technique de géoréférencement direct) et de leurs sources d 'erreurs. Les aspects liés à la performance du système, telles que la précision et la densité des informations, sont présentés. Les grandes quantités de données acquises par cette technique nécessitent un traitement spécifique pour les rendre utilisables. Les phases d 'acquisition et de traitement, du calcul de trajectoire au produit final, sont décrites. Finalement, quelques exemples pratiques de relevés héliportés obliques en terrain montagneux viennent illustrer les capacités de cette technologie., Vallet Julien. La lasergrammétrie aéroportée, approches théoriques, concepts, méthodes. In: Collection EDYTEM. Cahiers de géographie, numéro 12, 2011. Images et modèles 3D en milieux naturels. pp. 29-40.

In this paper, a newly-developed direct georeferencing system for the guidance, navigation and control of lightweight unmanned aerial vehicles (UAVs), having a weight limit of 5 kg and a size limit of 1.5 m, and for UAV-based surveying and remote sensing applications is presented. The system is intended to provide highly accurate positions and attitudes (better than 5 cm and 0.5°) in real time, using lightweight components. The main focus of this paper is on the attitude determination with the system. This attitude determination is based on an onboard single-frequency GPS baseline, MEMS (micro-electro-mechanical systems) inertial sensor readings, magnetic field observations and a 3D position measurement. All of this information is integrated in a sixteen-state error space Kalman filter. Special attention in the algorithm development is paid to the carrier phase ambiguity resolution of the single-frequency GPS baseline observations. We aim at a reliable and instantaneous ambiguity resolution, since the system is used in urban areas, where frequent losses of the GPS signal lock occur and the GPS measurement conditions are challenging. Flight tests and a comparison to a navigation-grade inertial navigation system illustrate the performance of the developed system in dynamic situations. Evaluations show that the accuracies of the system are 0.05° for the roll and the pitch angle and 0.2° for the yaw angle. The ambiguities of the single-frequency GPS baseline can be resolved instantaneously in more than 90% of the cases.

This paper is aimed at analysing the influence of the vertical deflection (DOV) in direct georeferencing (DG) of image data from an aerial digital frame camera. Without considering the value of the DOV, a systematic error is involved in the determination of the point position. This investigation has been carried out considering several values of the vertical deviation and, for each of them, the vertical and horizontal error obtained by varying the FOV (Field of View) over the altitude has been analysed.

Durch die technologische Weiterentwicklung, Minituarisierung und kosteng��nstigere Herstellung von Sensoren wie GNSS-Empf��nger, inertiale Messeinheiten (Drehraten- und Beschleunigungssensoren), Magnetometer und Barometer werden unbemannte Luftfahrzeuge (uLFZ, engl. unmanned aerial vehicles - UAV) f��r die Nahbereichsluftbildphotogrammetrie immer h��ufiger verwendet. Eine L��cke zwischen herk��mmlichen terrestrischen Messmethoden und aufw��ndigen bemannten Luftbild-Flugmissionen k��nnte so eventuell geschlossen werden. Unter der Verwendung eines uLFZ des Herstellers twins.nrn wurden Untersuchungen zur direkten Georeferenzierung von uLFZ-Luftbildern, d.h. der Bestimmung der Position und der Orientierung von Fotos im 3D-Raum (��u��ere Orientierung), vorgenommen. Das prim��re Ziel der Arbeit war, die bisherige Arbeiten der Forschungsgruppe Photogrammetrie am Department f��r Geod��sie und Geoinformation an der Technischen Universit��t Wien weiterzuf��hren und die bisher erreichten Genauigkeiten der direkten Georeferenzierung zu steigern. Durch die Implementierung eines Zweifrequenz-GPS-Empf��ngers am uLFZ sollten die Aufnahmepositionen der Luftbilder zu den Aufnahmezeitpunkten im Bereich von wenigen Zentimetern bestimmten werden k��nnen. Der Vorteil der direkten Georeferenzierung liegt im Verzicht oder zumindest bei der Reduktion von Passpunkten am Boden, die vor allem im unwegsamen Gel��nde oder in bewaldeten Gebieten aufwendig zu bestimmen sind. Zur Vermeidung des Deformationsverhaltens gr����erer Bildbl��cke unter Verwendung von wenigen Passpunkten, k��nnen die Parameter der ��u��eren Orientierung au��erdem als zus��tzliche Beobachtungen im B��ndelblockausgleich eingef��hrt werden. Die Einsatzm��glichkeit eines uLFZ und die Verwendung der direkten Georeferenzierung bei linearen Infrastrukturobjekten stellte das zweite Ziel der Arbeit dar. Aus diesem Grund und der Kooperation mit der ��BB-Infrastruktur AG, Stab Forschung und Entwicklung und Stab Vermessung und Datenmanagement, wurde diese M��glichkeit anhand eines Trassenabschnittes einer Eisenbahnstrecke in Herzogenburg (N��), in Flugh��hen von 40m und 70m getestet. F��r die Integration der synchronisierten Messdaten wurde ein erweitertes Kalman-Filter eingesetzt, das neben den Parametern der direkten Georeferenzierung auch die Biase der Sensoren der inertialen Messeinheit mitsch��tzt. Die Qualit��t der hier erprobten Methode konnte durch die Differenzbildung der Positionen und Orientierungen zwischen direkt und ��ber Passpunkte indirekt georeferenzierten Luftbildern verifiziert werden. Die daraus resultierenden einfachen Standardabweichungen der Differenzen zwischen direkter und indirekter Georeferenzierung nehmen bei beiden Fl��gen f��r den Roll- und Nick-Winkel, Driven by technological developments, miniaturisation and the cost-efficient construction of sensors such as GNSS-receivers, inertial measurement units, magnetometers and barometers, so called unmanned aerial vehicles (UAVs) are increasingly utilised in the field of close range airborne photogrammetry. Those UAVs might have the potential to close the gap between conventional terrestrial measurement methods and complex manned missions in aerial photogrammetry. In the context of this thesis, extensive investigations on the direct geo-referencing of aerial images, i.e. the determination of the current position and orientation of images in 3D-space, were carried out using a particular UAV manufactured by the company twins.nrn. The main goals of this thesis were the continuation of previous work carried out at the research group photogrammetry of the Department of Geodesy and Geoinformation at the Vienna university of Technology on the one hand, and to improve the accuracy of direct geo-referencing on the other hand. By implementing a dual-frequency GNSS receiver on the UAV, the current position at the exposure time of the images should be determined at an accuracy level of several centimetres. The main advantage of direct geo-referencing resides in the possibility to reduce the number of required control points on the ground, which are difficult to measure especially in impassable or forested areas, or even to omit them completely. The elements of the exterior orientation can serve as additional observation within the bundle block adjustment in the case of insufficient numbers of control points and to avoid the deformation of image bundles. The application for UAVs in the field of direct geo-referencing for the mapping of linear infrastructure facilities (such as rails) describes a second goal of the thesis. Therefore, the possibility to survey a railroad line in Herzogenburg (Lower Austria) was tested at flight altitudes of 40 and 70 metres in cooperation with the ��BB-Infrastruktur AG, Department of Research and Development and Department of Surveying and Data Management. For the integration of the synchronized measurement data an extended Kalman filter was applied. Hereby, not only the parameters of the direct geo-referencing, but also the biases of the inertial measurement unit were estimated. The quality of the method could be verified by analyzing the differences between the positions and orientations that were calculated directly on the one hand, and indirectly derived with the useage control-points on the other hand. The resulting standard deviations for both flights are in the range of

Unmanned aerial vehicles (UAVs), also known as unmanned airborne systems (UAS) or remotely piloted airborne systems (RPAS), are an established platform for close range airborne photogrammetry. Compared to manned platforms, the acquisition of local remote sensing data by UAVs is a convenient and very flexible option. For the application in photogrammetry UAVs are typically equipped with an autopilot and a lightweight digital camera. The autopilot includes several navigation sensors, which might allow an automated waypoint flight and offer a systematic data acquisition of the object resp. scene of interest. Assuming a sufficient overlap between the captured images, the position (3 coordinates: x, y, z) and the orientation (3 angles: roll, pitch, yaw) of the images can be estimated within a bundle block adjustment. Subsequently, coordinates of observed points that appear in at least two images, can be determined by measuring their image coordinates or a dense surface model can be generated from all acquired images by automated image matching. For the bundle block adjustment approximate values of the position and the orientation of the images are needed. To gather this information, several methods exist. We introduce in this contribution one of them: the direct georeferencing of images by using the navigation sensors (mainly GNSS and INS) of a low-cost on-board autopilot. Beside automated flights, the autopilot offers the possibility to record the position and the orientation of the platform during the flight. These values don’t correspond directly to those of the images. To compute the position and the orientation of the images two requirements must be fulfilled. First the misalignment angles and the positional differences between the camera and the autopilot must be determined (mounting calibration). Second the synchronization between the camera and the autopilot has to be established. Due to the limited accuracy of the navigation sensors, a small number of ground control points should be used to improve the estimated values, especially to decrease the amount of systematic errors. For the bundle block adjustment the calibration of the camera and their temporal stability must be determined additionally. This contribution presents next to the theory a practical study on the accuracy analysis of direct georeferenced UAV imagery by low-cost navigation sensors. The analysis was carried out within the research project ARAP (automated (ortho)rectification of archaeological aerial photographs). The utilized UAS consists of the airplane “MAJA”, manufactured by “Bormatec” (length: 1.2 m, wingspan: 2.2 m) equipped with the autopilot “ArduPilot Mega 2.5”. For image acquisition the camera “Ricoh GR Digital IV” is utilised. The autopilot includes a GNSS receiver capable of DGPS (EGNOS), an inertial measurement system (INS), a barometer, and a magnetometer. In the study the achieved accuracies for the estimated position and orientation of the images are presented. The paper concludes with a summary of the remaining error sources and their possible corrections by applying further improvements on the utilised equipment and the direct georeferencing process.

In recent years, Autonomous Unmanned Aerial Vehicles (AUAV) became popular among researchers across disciplines because they combine many advantages. One major application is monitoring and mapping. Their ability to fly beyond eye sight autonomously, collecting data over large areas whenever, wherever, makes them excellent platform for monitoring hazardous areas or disasters. In both cases rapid mapping is needed while human access isn't always a given. Indeed, current automatic processing of aerial photos using photogrammetry and computer vision algorithms allows for rapid orthophomap production and Digital Surface Model (DSM) generation, as tools for monitoring and damage assessment. In such cases, control point measurement using GPS is either impossible, or time consuming or costly. This work investigates accuracies that can be attained using few or none control points over areas of one square kilometer, in two test sites; a typical block and a corridor survey. On board GPS data logged during AUAV's flight are being used for direct georeferencing, while ground check points are being used for evaluation. In addition various control point layouts are being tested using bundle adjustment for accuracy evaluation. Results indicate that it is possible to use on board single frequency GPS for direct georeferencing in cases of disaster management or areas without easy access, or even over featureless areas. Due to large numbers of tie points in the bundle adjustment, horizontal accuracy can be fulfilled with a rather small number of control points, but vertical accuracy may not.

Doğrudan algılayıcı yöneltmesi veya doğrudan coğrafi yöneltme GNSS\IMU verileri kullanarak dış yöneltme parametrelerinin yer kontrol noktası kullanılmadan hesaplanmasıdır. Bu sistemin doğruluğu GNSS\IMU bütünleşik sistemin doğruluğuna bağlıdır. DGNSS (Diferential Global Navigation Satellite System) ve IMU (Inertial Measurement Unit)?nun birlikte kullanılmasıyla oluşan bütünleşik sistem, uçuş esnasında yaklaşık dış yöneltme elemanlarını belirlemektedir. Bu yöneltme elemanlarının doğruluğu GNSS ve IMU doğruluğuna bağlıdır. Bu çalışmada tek nokta, ağ yapısı ve ppp yöntemleriyle gnss çözümlerinin doğrudan algılayıcı yöneltmesi doğruluğuna etkisi değerlendirilmiştir. Test alanı 1296 km2 dir. 30 cm çözünürlüğünde 396 adet fotoğraf kullanılmıştır. Tek nokta çözüm yatay doğruluğu (X-Y) 23-30 cm , düşey doğruluğu 40 cm, ağ yapısı çözüm yatay doğruluğu 24-27 cm , düşey doğruluğu 37 cm ve ppp çözüm yatay doğruluğu 20-28 cm , düşey doğruluğu 44 cm hesaplanmıştır., Direct sensor orientation or direct georeferencing is the solution of exterior orientation parameters using GNSS\IMU data without ground control points. Accuracy of the system is based on GNSS\IMU integrated system accuracy. The integrated system containing DGNSS and IMU calculates the approximate exterior orientation parameters during the flight. The exterior orientation accuracy is based on GNSS and IMU accuracy. In this study, the effect of one point, network and PPP GNSS data processes without ground control point on the accuracy of the direct sensor orientation was evaluated. Test area is 1296 km2. It was used 393 images with 30 cm resolution. It was calculated that one point solution horizontal accuracies are (X-Y) 23-30 cm., vertical accuracy is (Z) 40cm, network solution horizontal accuracies are (X-Y) 24-27 cm, vertical accuracy is (Z) 37 cm and ppp solution horizontal accuracies are (X-Y) 20-28 cm, vertical accuracy is (Z) 37 cm.

Yılmaz, H. M ( Aksaray, Yazar ), Direct sensor orientation or direct georeferencing is the solution of exterior orientation parameters using GNSS\IMU data without ground control points. Accuracy of the system is based on GNSS\IMU integrated system accuracy. The integrated system containing DGNSS and IMU calculates the approximate exterior orientation parameters during the flight. The exterior orientation accuracy is based on GNSS and IMU accuracy. In this study, the effect of single point, network and PPP GNSS data processes without ground control point on the accuracy of the direct sensor orientation was evaluated. The area of the test region is approximately 1296 km(2). 393 images with 30 cm resolution were used in the study. It was calculated that single point solution horizontal accuracies are (X-Y) +/- 23-30 cm., vertical accuracy is (Z) +/- 40cm, network solution horizontal accuracies are (X-Y) +/- 24-27 cm, vertical accuracy is (Z) +/- 37 cm and PPP solution horizontal accuracies are (X-Y) +/- 20-28 cm, vertical accuracy is (Z) +/- 37 cm.

Die Beobachtung von Naturkatastrophen, Grosereignissen und Unfallen mit flugzeuggestutzten optischen Sensoren in Echtzeit ist ein derzeit wichtiges Thema in Forschung und Entwicklung. In diesem Zusammenhang wird die Leistungsfahigkeit von preisgunstigen Kamerasystemen fur Echtzeitanwendungen in Hinblick auf geometrische Genauigkeit, radiometrische Eigenschaften und Prozessierungszeiten evaluiert. Der Schwerpunkt liegt bei der Analyse der geometrischen Stabilitat von preisgunstigen Kameras im langjahrigen Betrieb und den Grenzen der direkten Georeferenzierung. Weiterhin wird eine echtzeitfahige Prozessierungskette mit einer GPU (Graphical Processing Unit) basierten Orthorektifizierungsmethode fur eine maximal mogliche Aufnahmerate von 5Hz vorgestellt.

A real time airborne monitoring system for monitoring of natural disasters, mass events, and large traffic disasters was developed in the last years at the German Aerospace Center (DLR). This system consists of an optical wide-angle camera system (3K system), a SAR sensor, an optical and microwave data downlink, an onboard processing unit and ground processing station with online data transmission to different end user portals. The development of the real time processing chain from the data acquisition to the ground station is still a very challenging task. In this paper, an overview of all relevant parts of the airborne optical mapping system is given and selected system processes are addressed and described in more detail. The experiences made in the flight campaigns of the last years are summarized with focus on the image processing part, e.g. reached accuracies of georeferencing and status of the traffic processors.

Remote sensing applications like disaster or mass event monitoring need the acquired data and extracted information within a very short time span. Airborne sensors can acquire the data quickly and on-board processing combined with data downlink is the fastest possibility to achieve this requirement. For this purpose, a new low-cost airborne frame camera system has been developed at the German Aerospace Center (DLR) named 3K-camera. The pixel size and swath width range between 15 cm to 50 cm and 2.5 km to 8 km respectively. Within two minutes an area of approximately 10 km x 8 km can be monitored. Image data are processed onboard on five computers using data from a real time GPS/IMU system including direct georeferencing. Due to high frequency image acquisition (3 images/second) the monitoring of moving objects like vehicles and people is performed allowing wide area detailed traffic monitoring.

Orthorectification is the process to convert imagery into map-accurate forms by removing sensor, satellite motion and terrain related geometric distortions from raw imagery and is one of the main pre-processing steps for application oriented evaluations. Although optical satellite data of high geometric resolution can be orthorectified to absolute geometric accuracies of about 5 m to several hundred meters - depending on the satellite mission - using the metadata information from the satellite data providers (e.g. satellite position, velocity and attitude at any instant of time during data acquisition, camera internal geometry), there is still a need to improve the geometric accuracy by using Ground Control Points (three dimensional real world coordinates, which have to be identified in the satellite image). The manual measurement of such Ground Control Points by operators is a time consuming work leading to a cost and time ineffective project completion. This paper proposes a method and procedure to automatically extract Ground Control Points from already existing orthorectified images of superior geometric quality (reference images), which are used to improve the geometric accuracy as well as to produce at least consistent data sets.

In this paper, a combined terrestrial laser scanning survey system is presented, where GPS can be used for direct georeferencing of the point clouds. The results of investigations of this system show that it is possible to achieve the coordinate accuracy of better than 1 cm in the point cloud, both in plane and height, at the object distance of up to about 70 m. In diesem Artikel wird ein kombiniertes terrestrisches Laserscanning-Vermessungssystem vorgestellt, bei dem GPS für eine direkte Georeferenzierung der Punktwolken verwendet werden kann. Die Ergebnisse der Prüfung dieses Systems zeigen, dass es möglich ist, eine Koordinatengenauigkeit von mehr als 1 cm in der Punktwolke, sowohl in Fläche wie Höhe, bei einer Objektdistanz von bis zu 70 m zu erreichen. Originally published in zfv 3/2010, Vol. 135, pp 151-159, Wissner-Verlag, Augsburg, 2010. Reproduced with permission from the publisher.

Unlike mobile survey systems, stationary survey systems are given very little direct georeferencing attention. Direct Georeferencing is currently being used in several mobile applications, especially in terrestrial and airborne LiDAR systems. Georeferencing of stationary terrestrial LiDAR scanning data, however, is currently performed indirectly through using control points in the scanning site. The indirect georeferencing procedure is often troublesome; the availability of control stations within the scanning range is not always possible. Also, field procedure can be laborious and involve extra equipment and target setups. In addition, the conventional method allows for possible human error due to target information bookkeeping. Additionally, the accuracy of this procedure varies according to the quality of the control used. By adding a dual GPS antenna apparatus to the scanner setup, thereby supplanting the use of multiple ground control points scattered throughout the scanning site, we mitigate not only the problems associated with indirect georeferencing but also induce a more efficient set up procedure while maintaining sufficient precision. In this paper, we describe a new method for determining the 3D absolute orientation of LiDAR point cloud using GPS measurements from two antennae firmly mounted on the optical head of a stationary LiDAR system. In this paper, the general case is derived where the orientation angles are not small; this case completes the theory of stationary LiDAR direct georeferencing. Simulation and real world field experimentation of the prototype implementation suggest a precision of about 0.05 degrees (~1 milli-radian) for the three orientation angles.

An important step in data processing from terrestrial laser scanning (TLS) is georeferencing, i.e. transformation of the scanner data (point clouds) into a real world coordinate system, which is important for their integration with other geospatial data. An efficient approach for this is direct georeferencing, whereby the position and orientation of the scanner can be determined in the field, similarly to the working routine of total stations. Thus the efficiency of the survey can be increased, and the project time and costs reduced. An important factor that affects the results of TLS surveys, especially those with direct georeferencing, is scanner calibration. In the recent years, the method of self-calibration used in photogrammetry has become popular for the recovery of systematic errors in laser scanners. This thesis has two main aims. The first one is to develop an approach for self-calibration of terrestrial laser scanners, which can be made available to users, and apply it to the calibration of a number of pulsed laser scanners in order to get a better insight into the systematic instrumental errors present in these instruments. The second aim is to investigate the possibilities for direct georeferencing in TLS in static applications, with the focus on the use of GPS for this purpose, and to develop a survey system based on the combination of TLS and GPS. An additional aim of the thesis is to make a systematic description of the error sources in TLS surveys, where direct georeferencing is employed. A good understanding of these error sources is necessary to secure the data accuracy. We subdivide these errors into four groups: instrumental, object-related, environmental and georeferencing. We have developed a unified approach for self-calibration of terrestrial laser scanners, where one can introduce stochastic information about all the estimated parameters, which helps in reducing their correlations. In part, it is possible to use direct georeferencing to determine the exterior orientation parameters of the scanner. We applied this approach to the self-calibration of the pulsed scanners Callidus CP 3200, Leica HDS 3000 and Leica Scan Station. The initial assumption was that the scanner systematic instrumental errors, or calibration parameters, were similar to those in a total station. However, other errors not explained by the “a priori” total station error model can be present in the scanners. We revealed two such errors – the scale errors in the vertical angles and horizontal directions in the scanners Callidus CP 3200 and Leica HDS 3000, respectively. Most systematic errors were estimated with relatively high precision and low correlations with other system parameters. We have developed a prototype combined survey system, which allows the user to use GPS for direct georeferencing of the scanner parallel to the scanning. In the current implementation, the system consists of the scanning system Leica Scan Station 2, 2 GPS receivers and antennas from Leica and a number of necessary accessories. The scanner position can be determined from RTK (or possibly Network-RTK) measurements with the accuracy of better than 1 cm, both in plane and height. The position of the backsight target can be determined from post-processing of static GPS measurements with similar accuracy. In order to estimate the accuracy of the combined system and its efficiency in a typical TLS survey, we carried out several test measurements. The results have shown that it is possible to achieve the coordinate accuracy of better than 1 cm at the object distance of up to 50 m. This is comparable to the accuracy of conventional direct georeferencing, i.e. when the scanner is centred over a known point. The time expenses for the test survey of a building located at KTH campus, starting from the planning and finishing with the georeferenced point cloud, were about 1.5 workdays. The time expenses could be reduced further if the system was installed on a moving platform during the fieldwork. Hence, the combined system can be successfully used for the surveys of built environments, e.g. engineering constructions and historical monuments, which can be carried out fast and with high accuracy. QC 20100806 3D laser scanning of engineering constructions and historical monuments

A near real time airborne monitoring system for monitoring of natural disasters, mass events, and large traffic disasters was developed in the last years at the German Aerospace Center (DLR). This system consists of an optical wide-angle camera system (3K system), a SAR sensor, an optical and microwave data downlink, an onboard processing unit and ground processing station with online data transmission to the DLR traffic and disaster portals. The development of the near real time processing chain from the data acquisition to the ground station is still a very challenging task. In this paper, an overview of all relevant parts of the airborne optical mapping system is given and selected system processes are addressed and described in more detail. The experiences made in the flight campaigns of the last years are summarized with focus on the image processing part, e.g. reached accuracies of georeferencing and status of the traffic processors.

Članak obrađuje osnove direktnog georeferenciranja, posebno je objašnjeno direktno georeferenciranje senzorom POS AV510. Detaljno se obrađuje kalibracija senzora, planiranje rada sa senzorom te inicijalizacija cijelog sustava. Na kraju se opisuje obrada podataka prikupljenih u radu sa senzorom., The article elaborates on the basics of direct georeferencing. In particular, direct georeferencing by the POS AV510 sensor is explained. Sensor calibration is elaborated in detail, as well as planning of work with the sensor and the initialisation of the whole system. At the end, the elaboration of the data collected during the work with sensor is described.

As a requirement for geocoding of raw hyperspectral line scan imaging data, the exterior orientation data set need to be obtained, especially in all-parametric geocoding proc-esses. Application such those defined within recent technologic project “ System for the Mul-tisensor Airborne Reconnaissance and Surveillance in the Crisis Situations and the Environment Protection“ , supported by Croatian Ministry of Science, Education and Sports, highlighted the need for position orientation system capable to measure and record inertial orientation and GPS position data at high frequency. Integration of the PGP imaging spectrograph (pushbroom scan-ner) system and Position and Orientation System (POS) was requested due to geocoding of raw data cube produced by pushbroom scanner. Several approaches were examined and one pre-sented here was chosen. Integration of hyperspectral imaging scanner, acquisition PC system and POS has been achieved by sharing reference PC clock time as common platform. In this digital interface configuration, PC clock is continuously updated and corrected by GPS UTC time ex-ternally provided by 5Hz GPS data and 1PPS signal. Thereafter, both the control and acquisition timing of hyperspectral imaging sensor and POS are referenced to PC GPS time. The impact of time synchronisation on imaging capabilities and spatial accuracy of such system will be dis- cussed. Position and Orientation System is based on iMAR iVRU-RSSC, the GPS coupled MEMS based Inertial Reference Unit, providing Roll, Pitch, Yaw, GPS Latitude, GPS Longitude and GPS Altitude data at maximum frequency of 200Hz, according to general requirement for line imaging mode utilization of hyperspectral pushbroom scanner, which states that read-out frequency of Inertial Measurement Unit (IMU) should be at least of those of scanner imaging frequency, implying that at least one set of mentioned orientation and position data for each line scan need to be available. The spatial and dynamic characteristics of chosen POS fulfils all high precision hyperspectral imaging application requirements based on ImSpectror V9 pushbroom scanner which is currently in use, as far as future high precision- high frequency electro-optical sensor requirements.

Sound title actually notes the utilization of hyperspectral imaging using airborne platform for the first time in Croatia. Specific application requirements highlited the need for Position and Orientation system capable to measure and record inertial orientation and GPS position data at high frequency, according to general requirement for line imaging mode utilization of airborne hyperspectral imaging scanner, which states that at least one set of position and orientation data should be available for each scan line. GPS proved as critical throughout few different tasks it has in: velocity and heading aiding for IMU (drift correction), time synchronization, trigerring and navigation. Furthermore, several electro-optical sensors were integrated in airborne sensor pod, with hyperspectral puhbroom scanner and hybrid IMU/GPS system (serving as Position and Orientation System) in its core. Complete airborne multisensor system is built off-the-shelf, integrated by using PC running under Windows OS and aimed to different applications, such as spectral detection of oil polution spill at sea, quality monitoring of water in lakes and rivers and explosives polution detection at military fire range, etc. Good understanding of different application requirements, along with the characteristics and design specification of state of the art sensors, led to system integration, which has proved as operational during first flight tests and has already scheduled for airborne mapping campaignes over mine contaminated area in Croatia.

One of the first essential steps in response to a crisis event is to provide current, precise, and rapid information about the extent of the event, the affected population and infrastructure (e.g., information for relief teams). Experiences in crisis mapping show, that remote sensing data are an important information source to get an overview of the situation. For an efficient use of geo-information before or during a crisis of any kind, all information should be orthorectified. Satellite data are delivered normally geocoded with varying accuracy. However, today orthorectification without ground control points (GCP) using only ephemeris and attitude data measured on board the satellite provide an absolute accuracy of about 20 m to 1 km (depending on the satellite). For the intended applications like change detection this accuracy is not sufficient. For this purpose, accuracy in the sub-pixel range is necessary requiring a precise orthorectification. Different methods deployed in different software packages are analyzed and compared in this paper. They are chosen depending on the available metadata. To get an objective comparison of the different orthorectification methods, their accuracy is determined for several test datasets in this study. Additionally to the comparison of the accuracy, further criteria are analyzed like the potential of the algorithm for optimization and automation and the computing time needed, since the timely supply of information is also one of the most important requirements in crisis respond mapping. Results using the commercially available software packages Erdas Imagine, PCI Geomatics and ENVI are compared to products of the in-house developed software XDibias of the German Aerospace Center (DLR). All programs result in high accuracy. Differences are experienced in the computing times and userfriendlyness. While the commercial programs are very user friendly, knowledge about the details of the in-house developed software are very helpful and the automation potential of it has already been proven.

During the HRS (High Resolution Stereo) Scientific Assessment Program the French space agency CNES delivered data sets from the HRS camera system with high precision ancillary data. Two test data sets from this program were evaluated: one is located in Germany, the other in Spain. The first goal was to derive orthoimages and digital surface models (DSM) from the along track stereo data by applying the rigorous model with direct georeferencing and without ground control points (GCPs). For the derivation of DSM, the stereo processing software, developed at DLR for the MOMS-2P three line stereo camera was used. As a first step, the interior and exterior orientation of the camera, delivered as ancillary data from positioning and attitude systems were extracted. A dense image matching, using nearly all pixels as kernel centers provided the parallaxes. The quality of the stereo tie points was controlled by forward and backward matching of the two stereo partners using the local least squares matching method. Forward intersection lead to points in object space which are subsequently interpolated to a DSM in a regular grid. DEM filtering methods were also applied and evaluations carried out differentiating between accuracies in forest and other areas. Additionally, orthoimages were generated from the images of the two stereo looking directions. The orthoimage and DSM accuracy was determined by using GCPs and available reference DEMs of superior accuracy (DEM derived from laser data and/or classical airborne photogrammetry). As expected the results obtained without using GCPs showed a bias in the order of 5–20 m to the reference data for all three coordinates. By image matching it could be shown that the two independently derived orthoimages exhibit a very constant shift behavior. In a second step few GCPs (3–4) were used to calculate boresight alignment angles, introduced into the direct georeferencing process of each image independently. This method improved the absolute accuracy of the resulting orthoimages and DSM significantly.

One of the main problems of today's Airborne Laser Scanning (ALS) systems is the lack of reliable data QA/QC (Quality Assurance/ Quality Control) within or shortly after the airborne survey campaign. This thesis presents the development of methods to perform automated processing and QA/QC of ALS data during data acquisition (in-flight). The backbone of these methods is an error propagation algorithm that estimates the expected accuracy of the point-cloud. The error propagation considers the uncertainties induced by the direct georeferencing (DG) and the changing scanning geometry. A novel methodology that derives the scanning geometry directly from the point-cloud and computes a final quality indicator for every laser point is developed. To predict the accuracy of the navigation solution, this research also proposes a methodology to estimate in realtime (RT) the likelihood of fixing the differential carrier-phase ambiguities during post-processing. Furthermore, an innovative procedure to describe the quality of digital terrain models (DTM) derived from ALS data is presented. The successful implementation of these concepts into a fully functional in-flight quality monitoring tool embedded in an ALS system is demonstrated. The proposed tool incorporates RT GPS/INS processing and point-cloud georeferencing. The general performance of the tool, the validity of the quality indicators and the achievable improvement in efficiency for ALS data acquisition are assessed in airborne surveys. It is shown that when using RTK GPS (real-time kinematics) as positioning mode, the tool can provide point-clouds with sub-decimeter accuracy in RT.

We carry out a comprehensive feasibility study for a real-time cm-level localisation of a predefined terrestrial target from a MAV-based autonomous platform. Specifically, we conduct an error propagation analysis which quantifies all potential error sources, and accounts for their respective contribution to the final result. Furthermore, we provide a description of a practical MAV system using the available technology and of-the-shelf components. We demonstrate that, indeed, the desired localisation precision of a few centimetres may be realistically achieved under a set of necessary constraints.