DGPF-Project: Evaluation of Digital Photogrammetric Camera Systems Geometric Performance

Jacobsen, Karsten; Cramer, Michael; Ladstädter, Richard; Ressl, Camillo; Spreckels, Volker

doi:10.1127/1432-8364/2010/0042

Cited by 34 publications

(21 citation statements)

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“…Without GPS coordinates of the projection centers the focal length and principal point location cannot be determined significantly due to high correlation with the EO-parameters. On the other side the significant parameters of the general 12 additional parameters of BLUH (Jacobsen 2007) and the special parameters for the image corners (Jacobsen et al 2010) are required and lead to improvement of the results. OrientAL (Karel et al, 2013): In order to better cope with the large perspective distortions between views from different cameras on the platform, OrientAL extracted and described image feature points found in virtual views generated from the original aerial photos by applying affine transformations onto…”

Section: Bluhmentioning

confidence: 99%

Orientation of Oblique Airborne Image Sets – Experiences From the Isprs/Eurosdr Benchmark on Multi-Platform Photogrammetry

Gerke

Nex

Remondino

et al. 2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:During the last decade the use of airborne multi camera systems increased significantly. The development in digital camera technology allows mounting several mid-or small-format cameras efficiently onto one platform and thus enables image capture under different angles. Those oblique images turn out to be interesting for a number of applications since lateral parts of elevated objects, like buildings or trees, are visible. However, occlusion or illumination differences might challenge image processing. From an image orientation point of view those multi-camera systems bring the advantage of a better ray intersection geometry compared to nadir-only image blocks. On the other hand, varying scale, occlusion and atmospheric influences which are difficult to model impose problems to the image matching and bundle adjustment tasks. In order to understand current limitations of image orientation approaches and the influence of different parameters such as image overlap or GCP distribution, a commonly available dataset was released. The originally captured data comprises of a state-of-the-art image block with very high overlap, but in the first stage of the so-called ISPRS/EUROSDR benchmark on multi-platform photogrammetry only a reduced set of images was released. In this paper some first results obtained with this dataset are presented. They refer to different aspects like tie point matching across the viewing directions, influence of the oblique images onto the bundle adjustment, the role of image overlap and GCP distribution. As far as the tie point matching is concerned we observed that matching of overlapping images pointing to the same cardinal direction, or between nadir and oblique views in general is quite successful. Due to the quite different perspective between images of different viewing directions the standard tie point matching, for instance based on interest points does not work well. How to address occlusion and ambiguities due to different views onto objects is clearly a non-solved research problem so far. In our experiments we also confirm that the obtainable height accuracy is better when all images are used in bundle block adjustment. This was also shown in other research before and is confirmed here. Not surprisingly, the large overlap of 80/80% provides much better object space accuracyrandom errors seem to be about 2-3fold smaller compared to the 60/60% overlap. A comparison of different software approaches shows that newly emerged commercial packages, initially intended to work with small frame image blocks, do perform very well.

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Section: Bluhmentioning

confidence: 99%

Orientation of Oblique Airborne Image Sets – Experiences From the Isprs/Eurosdr Benchmark on Multi-Platform Photogrammetry

Gerke

Nex

Remondino

et al. 2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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“…The former often used Ebner parameters during the evaluation test of the German Society of Photogrammetry and Remote Sensing (Jacobsen et al 2010) has been shown as not useful for digital camera images, while the extension to the Grün-parameters was helpful for determination and consideration of systematic image errors. Nevertheless the Grün-parameters are general parameters, not able to respect special geometric problems.…”

Section: Self-calibrationmentioning

confidence: 99%

“…Parameters: only 81 -88 The UltraCam Eagle is fusing the 9 panchromatic sub-images of the 4 sub-cameras together. With the so called "monolithic stitching" (Ladstädter et al 2010) the panchromatic sub-images are fitted to the green image which is based on one CCD-array with approximately linear three times lower resolution. This stitching improved the image geometry clearly against the former merging of sub-images; nevertheless the special additional parameters for the sub-images (parameters 32-73) have to be checked.…”

Section: Ultracam Eaglementioning

confidence: 99%

Performance of Large-Format Digital Cameras

Jacobsen

2014

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:Based on test blocks and standard production blocks Z/I Imaging DMCII-140, 230 and 250 as well as UltraCam Eagle images have been analyzed by bundle block adjustment with self calibration. By analysis of image coordinate residuals it is possible to check remaining systematic image errors and to update the set of additional parameters to the required combination. The Hannover program BLUH is using a basic set of 12 additional parameters which is a combination between geometric parameters and Fourier parameters in polar coordinates. In addition it is necessary to use a set of special additional parameters for the combination of the 9 UltraCam sub-CCDs. CCDs are often not flat enough, causing a bending of the edges. For the correct handling of such effects, special additional parameters are required to eliminate or at least reduce remaining systematic effects at image corners. For all DMCII-blocks with 5cm, 7cm, 9cm and 20cm GSD the root mean square size of the systematic image errors with 0.05pixels is very small. Only the basic set of 12 additional parameters is required, the special parameters for the image corners did not improve the accuracy determined with independent check points. Against former results with UltraCam images the monolithic stitching of the panchromatic sub-images to the green image improved the image geometry, nevertheless for reaching the highest accuracy the full set of 52 additional parameters is required, leading to systematic image errors in the root mean square of approximately 0.2pixels. This seems to be small, but it is causing a model deformation up to more as 1.0 GSD in the height, while in the case of the DMCIIimages the model deformation did not exceed 0.2 GSD in Z. The major reason for the UltraCam Eagle image deformation seems to be caused by corner effects of the green reference image. Such an effect can be avoided with a better calibration. The DMCII and the UltraCam Eagle images were improved by the firm ware for edge enhancement, influencing also the effective image resolution, determined by edge analysis. No real loss of the effective against the nominal resolution can be seen. Nevertheless the UltraCam Eagle images are a little noisy, which may be caused by the edge enhancement and by the imaging in January.

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“…Depending on the fixing of the CCD-arrays in the cameras, the flatness may depend on the temperature. This effect can be determined with the special parameters 81 up to 88 (Jacobsen et al 2010). Also the principal point (x and y) as well as the focal length can be included as unknown.…”

Section: Data Setmentioning

confidence: 99%

“…Especially the exact camera geometry and geometric stability has been analyzed. The precise image geometry was determined by bundle block adjustment with self calibration by program system BLUH (Jacobsen 2007, Jacobsen et al 2010. By self calibration the details of inner orientation can be determined, while the boresight misalignment can be extracted from exterior orientation.…”

Section: Introductionmentioning

confidence: 99%

Sub-Camera Calibration of a Penta-Camera

Jacobsen¹,

Gerke²

2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:Penta cameras consisting of a nadir and four inclined cameras are becoming more and more popular, having the advantage of imaging also facades in built up areas from four directions. Such system cameras require a boresight calibration of the geometric relation of the cameras to each other, but also a calibration of the sub-cameras.Based on data sets of the ISPRS/EuroSDR benchmark for multi platform photogrammetry the inner orientation of the used IGI Penta DigiCAM has been analyzed. The required image coordinates of the blocks Dortmund and Zeche Zollern have been determined by Pix4Dmapper and have been independently adjusted and analyzed by program system BLUH. With 4.1 million image points in 314 images respectively 3.9 million image points in 248 images a dense matching was provided by Pix4Dmapper. With up to 19 respectively 29 images per object point the images are well connected, nevertheless the high number of images per object point are concentrated to the block centres while the inclined images outside the block centre are satisfying but not very strongly connected. This leads to very high values for the Student test (T-test) of the finally used additional parameters or in other words, additional parameters are highly significant.The estimated radial symmetric distortion of the nadir sub-camera corresponds to the laboratory calibration of IGI, but there are still radial symmetric distortions also for the inclined cameras with a size exceeding 5µm even if mentioned as negligible based on the laboratory calibration. Radial and tangential effects of the image corners are limited but still available. Remarkable angular affine systematic image errors can be seen especially in the block Zeche Zollern. Such deformations are unusual for digital matrix cameras, but it can be caused by the correlation between inner and exterior orientation if only parallel flight lines are used. With exception of the angular affinity the systematic image errors for corresponding cameras of both blocks have the same trend, but as usual for block adjustments with self calibration, they still show significant differences.Based on the very high number of image points the remaining image residuals can be safely determined by overlaying and averaging the image residuals corresponding to their image coordinates. The size of the systematic image errors, not covered by the used additional parameters, is in the range of a square mean of 0.1 pixels corresponding to 0.6µm. They are not the same for both blocks, but show some similarities for corresponding cameras.In general the bundle block adjustment with a satisfying set of additional parameters, checked by remaining systematic errors, is required for use of the whole geometric potential of the penta camera. Especially for object points on facades, often only in two images and taken with a limited base length, the correct handling of systematic image errors is important. At least in the analyzed data sets the self calibration of sub-cameras by bundle block adjustment suffers from th...

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DGPF-Project: Evaluation of Digital Photogrammetric Camera Systems Geometric Performance

Cited by 34 publications

References 0 publications

Orientation of Oblique Airborne Image Sets – Experiences From the Isprs/Eurosdr Benchmark on Multi-Platform Photogrammetry

Orientation of Oblique Airborne Image Sets – Experiences From the Isprs/Eurosdr Benchmark on Multi-Platform Photogrammetry

Performance of Large-Format Digital Cameras

Sub-Camera Calibration of a Penta-Camera

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