An Evaluation on Different Number of Ground Control Points in Unmanned Aerial Vehicle Photogrammetric Block (original) (raw)
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Effect of Camera Optimization on 3D Location Accuracy in UAV Photogrammetry
III. International Istanbul Current Scientific Research Congress, 2023
The quality of the final products produced with unmanned aerial vehicle (UAV) photogrammetry is increasing day by day; along with this, the process steps in the photogrammetric process are detailed, and work on quality improvement of products continues. Camera optimization is an important step in the processing of images in digital photogrammetry. Camera alignment optimization is an optimization process before dense point cloud generation with the help of a sparse point cloud generated after reciprocal orientation, which is the preliminary stage of creating a viable substantive model based on the dense point cloud. This process is recommended to users in package software in order to increase geometric accuracy and in light of the findings on absolute orientation, its impact is understood. In this work, the impact of camera optimization on the quality of threedimensional (3D) models created from RGB UAV aerial photos collected with polygonal flights was examined. The data of the study were collected with a polygonal flight from a height of 120m with a DJI Phantom IV Pro V2 RGB UAV. With the help of these data, digital surface models were produced separately with and without optimization. In order to compare all of the pixels models contain, model-based methodologies were used for 3D compatibility analyses. Compatibility analyzes were carried out for the building, open land, and forest classes in the land, and in addition, the analysis of the effect of land slope on the results was also examined. Interior orientation can be automatically resolved with the metadata of the UAV cameras, therefore, there is no need to interfere with the parameters during the optimization process. In this study, radial distortion (k4) and skew (b1, b2) parameters were included in addition to the parameters presented by default in optimization, and when the results were examined, an improvement in absolute orientation was observed, while serious deterioration in model accuracy was detected. This disruptive effect was statistically explained in detail and the necessity of the optimization was highlighted.
Assessment of UAV-photogrammetric mapping accuracy based on variation of ground control points
International Journal of Applied Earth Observation and Geoinformation, 2018
Civil engineering uses digital elevation models (DEMs) and orthophotos as basic material to be able to design and execute any project. UAV photogrammetry has made it possible to obtain this type of information in an economic and practical way. However, it is necessary to know the accuracy of the data and that it is within the admissible limits. There are many factors that affect the accuracy of products resulting from UAV photogrammetry. Of all of these, the effect of the number of ground control points (GCPs) and their distribution in the study area are especially significant. Different distributions of GCPs have been studied to try to optimize the products obtained by UAV photogrammetry. Of all the distributions tested, the best results were obtained with edge distribution and stratified distribution. Therefore, it is necessary to place GCPs around the edge of the study area to minimize planimetry errors. In addition, it is advisable to create a stratified distribution inside the study area with a density of around 0.5-1 GCP × ha −1 to minimize altimetry errors. The combination of these two distributions minimizes the total error obtained.
Simulation and Analysis of Photogrammetric Uav Image Blocks: Influence of Camera Calibration Error
ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences
Unmanned aerial vehicles (UAV) are increasingly used for topographic mapping. The camera calibration for UAV image blocks can be performed a priori or during the bundle block adjustment (self-calibration). For an area of interest with flat, corridor configuration, the focal length of camera is highly correlated with the height of camera. Furthermore, systematic errors of camera calibration accumulate on the longer dimension and cause deformation. Therefore, special precautions must be taken when estimating camera calibration parameters. In this paper, a simulated, error-free aerial image block is generated. error is then added on camera calibration and given as initial solution to bundle block adjustment. Depending on the nature of the error and the investigation purpose, camera calibration parameters are either fixed or re-estimated during the bundle block adjustment. The objective is to investigate how certain errors in the camera calibration impact the accuracy of 3D measurement without the influence of other errors. All experiments are carried out with Fraser camera calibration model being employed. When adopting a proper flight configuration, an error on focal length for the initial camera calibration can be corrected almost entirely during bundle block adjustment. For the case where an erroneous focal length is given for pre-calibration and not re-estimated, the presence of oblique images limits the drift on camera height hence gives better camera pose estimation. Other than that, the error on focal length when neglecting its variation during the acquisition (e.g., due to camera temperature increase) is also investigated; a bowl effect is observed when one focal length is given in camera pre-calibration to the whole image block. At last, a local error is added in image space to simulate camera flaws; this type of error is more difficult to be corrected with the Fraser camera model and the accuracy of 3D measurement degrades substantially.
Comparative Flight Direction Methods of Photogrammetry in Unmanned Aerial Vehicle (UAV) Technology
Advances in Social Science, Education and Humanities Research
Indonesia is an archipelago country which has varieties of cultural heritage, both ancestral heritage and the remnants from the Dutch colonial period. Quantity, variations and locations scattered throughout Indonesia are the problem in making documentation. Photogrammetry is considered suitable for documenting cultural heritage buildings because it focuses on the methods and devices used as an important key to getting good data so that it can be processed. Villa Isola is one of the heritage buildings of the Dutch colonial government which was chosen as the research object because it has an irregular and dynamic shape. This paper studies the method of taking the visual data photogrammetry of a building as well as the landscape around it with 45 degree and 90 degree angle flight directions. The results of the study found that the comparison of the results of the processing of the two UAV flying methods above provided more important information. Furthermore, the picture of the number of clouds and meetings at a 45 degrees flying angle is more accurate than 90 degrees flying angle. Due to shorter duration data processing and lower memory consumption of devices of 45 degrees flying angle of devices.
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UAV-DAP (unmanned aerial vehicle-digital aerial photogrammetry) has become one of the most widely used geomatics techniques in the last decade due to its low cost and capacity to generate high-density point clouds, thus demonstrating its great potential for delivering high-precision products with a spatial resolution of centimetres. The questions is, how should it be applied to obtain the best results? This research explores different flat scenarios to analyse the accuracy of this type of survey based on photogrammetric SfM (structure from motion) technology, flight planning with ground control points (GCPs), and the combination of forward and cross strips, up to the point of processing. The RMSE (root mean square error) is analysed for each scenario to verify the quality of the results. An equation is adjusted to estimate the a priori accuracy of the photogrammetric survey with digital sensors, identifying the best option for μxyz (weight coefficients depending on the layout of bot...
Metrology and Measurement Systems, 2018
Understanding the factors that influence the quality of unmanned aerial vehicle (UAV)-based products is a scientifically ongoing and relevant topic. Our research focused on the impact of the interior orientation parameters (IOPs) on the positional accuracy of points in a calibration field, identified and measured in an orthophoto and a point cloud. We established a calibration field consisting of 20 materialized points and 10 detailed points measured with high accuracy. Surveying missions with a fixed-wing UAV were carried out in three series. Several image blocks that differed in flight direction (along, across), flight altitude (70 m, 120 m), and IOPs (known or unknown values in the image-block adjustment) were composed. The analysis of the various scenarios indicated that fixed IOPs, computed from a good geometric composition, can especially improve vertical accuracy in comparison with self-calibration; an image block composed from two perpendicular flight directions can yield be...
IOP Conference Series: Earth and Environmental Science, 2014
Photogrammetry is the earliest technique used to collect data for topographic mapping. The recent development in aerial photogrammetry is the used of large format digital aerial camera for producing topographic map. The aerial photograph can be in the form of metric or non-metric imagery. The cost of mapping using aerial photogrammetry is very expensive. In certain application, there is a need to map small area with limited budget. Due to the development of technology, small format aerial photogrammetry technology has been introduced and offers many advantages. Currently, digital map can be extracted from digital aerial imagery of small format camera mounted on light weight platform such as unmanned aerial vehicle (UAV). This study utilizes UAV system for large scale stream mapping. The first objective of this study is to investigate the use of light weight rotary-wing UAV for stream mapping based on different flying height. Aerial photograph were acquired at 60% forward lap and 30% sidelap specifications. Ground control points and check points were established using Total Station technique. The digital camera attached to the UAV was calibrated and the recovered camera calibration parameters were then used in the digital images processing. The second objective is to determine the accuracy of the photogrammetric output. In this study, the photogrammetric output such as stereomodel in three dimensional (3D), contour lines, digital elevation model (DEM) and orthophoto were produced from a small stream of 200m long and 10m width. The research output is evaluated for planimetry and vertical accuracy using root mean square error (RMSE). Based on the finding, sub-meter accuracy is achieved and the RMSE value decreases as the flying height increases. The difference is relatively small. Finally, this study shows that UAV is very useful platform for obtaining aerial photograph and subsequently used for photogrammetric mapping and other applications.
2019
UAVs systems are heavily adopted nowadays to collect high resolution imagery with the purpose of documenting and mapping environment and cultural heritage. Such data are currently processed by programs based on the Structure from Motion (SfM) concept, coming from the Computer Vision community, rather than from classical Photogrammetry. It is interesting to check whether some widely accepted rules coming from oldfashioned photogrammetry still holds: the relation between accuracy and GSD, the ratio between the altimetric and planimetric accuracy, accuracy estimated on GCPs vs that estimated with CPs. Also, not all the SfM programs behave in the same way. To face the envisaged aspects, the paper adopts a comparative approach, as several programs are used, and numerous configurations considered. The University of Pavia established a test field at a sandpit located in the Province of Pavia, in northern Italy, where several flights were performed by the multi-rotor HEXA-PRO UAV, equipped ...
Advancement in aviation technology has greatly improved the processes of acquiring images for map production. Over the years images acquired by aircraft and satellite technologies have been the only sources of images for map production. This technically made map production by photogrammetric method an esoteric endeavour available to advanced technologies. The huddles in the way of its use in developing countries included cost, time, expertise and others. In recent times, the combination of advancements in computer and aviation technologies has produced robotic aircrafts called drones which though unmanned, can be used to acquire images from the air and almost in any location even impossible for regular aircraft imaging system. This innovation is also cheap to acquire and cheap to deploy and to maintain. So, research focus has turned to investigating the use of drone captured images in mapping large geographic areas. Therefore, this project deals with investigation into the geometric accuracy of a drone acquired block of images using analytical two platform orientation and spatial intersection. The aim of this project is to investigate the geometric accuracy of a drone acquired block of images. The drone technology used is an Unmanned Fixed-Wing Aircraft System. To fulfil the aim of this project, block of images of Faculty of Education, University of Lagos acquired from an Unmanned Fixed-Wing Aircraft System was obtained. A stereo pair was extracted from the block of images with 60% overlap. Measurement of image coordinates of control, check and detail points was achieved using AutoCAD software as a mono-comparator simulator. The ground survey for control and check points establishment was achieved using Promark 3 Differential Global Positioning System (DGPS). MATLAB program was developed to compute the exterior orientation parameters of the stereo image and subsequently the 3D object space coordinates of control, check and detail points were computed. Statistical analysis was done to evaluate the geometric accuracy of the stereo image using coordinates obtained from ground and photogrammetric survey methods. The root mean square error (RMSE) in plan was 20-50cm for positional accuracy while that for height was 40cm. The relative error obtained for distance measurement is approximately 1:100 while that for area measurements are approximately 0.3:100 and 7:100. Based on the findings of this study, it is concluded that 1 drone (UAV) techniques can replace other methods of surveying as the main method of data capture for engineering projects, boundary mapping and topographical surveying.