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Medium Format Digital Cameras: Standards and Specifications for Calibration and Stability Analysis

Medium Format Digital Cameras: Standards and Specifications for Calibration and Stability Analysis. A. F. Habib Digital Photogrammetry Research Group http://dprg.geomatics.ucalgary.ca Department of Geomatics Engineering University of Calgary, Canada. Introduction.

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Medium Format Digital Cameras: Standards and Specifications for Calibration and Stability Analysis

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  1. Medium Format Digital Cameras:Standards and Specifications for Calibration and Stability Analysis A. F. Habib Digital Photogrammetry Research Group http://dprg.geomatics.ucalgary.ca Department of Geomatics Engineering University of Calgary, Canada

  2. Introduction

  3. Operational Photogrammetric Systems • Classification of digital cameras (photogrammetric perspective): • Line Cameras (ADS 40) • Large format digital frame cameras (??) • Multi-head digital frame cameras (DMCTM, UltrCam, DiMAC 2.0) • Medium-format Digital Cameras (MFDC): • Mass-produced MFDC for mapping purposes (DSS, DiMAC Light) • MFDC for mapping purposes from data providers (DAC 101) • Amateur medium format digital cameras (AMFDC)

  4. MFDC from Data Providers • DAC 101: Camera assembled by Selkirk Remote Sensing • The camera utilizes a 60mm Rollei lens with a Rodenstock Apo-Sironar shutter and a 22 megapixel digital back (5440x4080 Imacon Ixpress 132 Digital Back with 9µm pixel size)

  5. Amateur Medium-Format Digital Cameras Kodak 14n Canon EOS 1D AMFDC SONY 717

  6. Large Format Analog Cameras (LFAC) WILD RC10

  7. Medium Format Digital Cameras (AMFDC) SONY DSC F717

  8. MFDC: Relevant Questions • Is the use of amateur MFDC in mapping applications a temporary or permanent phenomenon? • How to develop meaningful standards for evaluating the outcome from the calibration procedure? • How to develop meaningful standards for evaluating the stability of the involved camera? • Is there a flexibility in choosing the stability analysis tool, which is commensurate with the geo-referencing procedure to be implemented for this camera?

  9. Standards and Specification Philosophy • Regulating the use of imaging systems in mapping applications can be done through either: • Having a government body (third party) responsible for the evaluation/calibration of the imaging systems. • Widely adopted for analog cameras (USGS, NRCAN). • Certifying the imaging systems. • Suitable for digital imaging systems intended for mapping applications (DMCTM, ADS 40, UltrCam, DiMAC, DSS, etc.). • Transferring the responsibility to the data provider after establishing a set of standards and specifications. • Appropriate for AMFDC and MFDC from data providers. • Calibration, stability analysis, achievable accuracy.

  10. Indoor Calibration Test Field

  11. Indoor Calibration Test Field

  12. Indoor Calibration Test Field

  13. Indoor Calibration Test Field

  14. Tested Cameras (Example)

  15. Tested Cameras (Example)

  16. Data Acquisition

  17. Calibration Images Center High & Low

  18. Calibration Images Left High & Low

  19. Calibration Images Right High & Low

  20. Calibration Specifications • Variance component of unit weight: • Tier I < 1 Pixel • Tier II < 1.5 Pixels • Tier III < N/A Pixels • No correlation should exist among the estimated parameters • Standard deviations of the estimated IOP parameters (xp, yp, c): • Tier I < 1 Pixel • Tier II < 1.5 Pixels • Tier III < N/A

  21. ? ≡ Stability Analysis: Proposed Approach Top View Side View P.C.II P.C.I cII cI Bundle I Bundle II Original Image Grid Points Distortion-free Grid Points using IOPI Distortion-free Grid Points using IOPII

  22. Stability Analysis: Proposed Approach • Method 1: Zero Rotation (ZROT) • Same perspective center (no shift allowed) • Parallel image coordinate systems (no rotation allowed) P.C. Ray from Bundle I Ray from Bundle II Offset cI cII Original Image Points Distortion-free Grid Point using IOPI Distortion-free Grid Point using IOPII Projected Grid Point of IOPII

  23. Spatial Offset Stability Analysis: Proposed Approach • Method 2: Rotation (ROT) • Same perspective center (no shift allowed) • Rotation allowed P.C. (0, 0, 0) pI (xI, yI,-cI) R (, , ) pII (xII, yII,-cII) Original Image Points Distortion-free Grid Point using IOPI Distortion-free Grid Point using IOPII Projected Grid Point of IOPII

  24. Offset Stability Analysis: Proposed Approach • Method 3: Single Photo Resection (SPR) • Object space comparison • Spatial and rotational offsets permitted P.C.I cI cII P.C.II Original Image Points Distortion-free Grid Point using IOPI Distortion-free Grid Point using IOPII Bundle I Back-projected Object Points Bundle II

  25. Stability Specifications • The similarity measure (RMSE offset) value is computed to express the degree of similarity between the bundles from two sets of IOPs. • The cameras must meet the following specifications to be deemed stable. • Tier I < 1 Pixel • Tier II < 1.5 Pixels • Tier III : N/A • A software is available for the calibration and stability analysis procedures.

  26. MFDC: Relevant Questions • Can the stability analysis be used for evaluating the equivalency of different distortion models? • Appropriate distortion models. • Should the standards for the calibration and stability analysis be expressed in terms of image or object space units? • What is the achievable accuracy from MFDC? • Geo-referencing method (GCP, GNSS-assisted, GNSS/INSS). • Number of tie points. • What are the applications most suited for MFDC? • Small blocks, in combination with LiDAR systems, in combination with high resolution satellite scenes.

  27. MFDC & Aerial Mapping • Kodak DCS-14n • CMOS (4536x 3024) • 50 mm Zeiss lens • Pixel size: 7.9x7.9 µm • 12 Photos • Flying height: 1200 m • GSD: 0.20 meters

  28. MFDC & Aerial Mapping Federal University of Parana, Brazil

  29. MFDC & Aerial Mapping Root Mean Square Error Analysis

  30. MFDC & Aerial Mapping Orthophoto generated for Kodak (left) and RC10 (right) imagery

  31. MFDC, LiDAR & Satellite Scenes

  32. Experimental Results: Dataset Lower Block Lower LIDAR Scan DSS: Lower Block

  33. 35.000 30.000 N/A NO Frames 25.000 Frame GPS 20.000 Lines(45) RMSE, m 15.000 Lines (138) Patches (45) 10.000 Patches (139) 5.000 0.000 0 1 2 3 4 5 6 7 8 9 10 15 40 Number of Control Points MFDC, LiDAR & Satellite Scenes

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