VIIIth International Congress of Photogrammetry: Reprints of papers

Fagerholm, P. O.; Lycken, L. E.; Thunberg, A.; Öhlin, K. A.

Bibliographic data

Multivolume work

Persistent identifier:: 1048861678

Title:: VIIIth International Congress of Photogrammetry

Sub title:: Stockholm, Sweden, July 17 - 26, 1956

Year of publication:: 1957

Place of publication:: Stockholm

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 1048861678

Language:: English

Other Title:: Paralleltitel: VIIIe Congrès International de Photogrammétrie

Editor:: Fagerholm, P. O.

Corporations:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Adapter:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Founder of work:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Other corporate:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Document type:: Multivolume work

Volume

Persistent identifier:: 1048997812

Title:: Reprints of papers

Scope:: circa 1120 Seiten in verschiedenen Seitenzählungen

Year of publication:: 1957

Place of publication:: Stockholm

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 1048997812

Illustration:: Illustrationen

Signature of the source:: ZS 312(12,4a)

Language:: French

Other Title:: Paralleltitel: Tirages a part

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Contributor:: Lycken, L. E.; Thunberg, A.; Öhlin, K. A.

Editor:: Fagerholm, P. O.

Corporations:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Adapter:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Founder of work:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Other corporate:: International Congress of Photogrammetry, 8., 1956, Stockholm; Board of the VIIIth International Congress of Photogrammetry

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2019

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: COMMISSION I

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Title:: Differences between Visual and Photographic Calibrations of Air Survey Cameras P. D. CARMAN AND H. BROWN

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Structure type:: Chapter

ure 5c, gistre- fs sont mes b l'obtu- In voit re 5d), ves de ots de traité, re dela e l'ap- le à sa ut dire e l’ob- 5. econde (deux sifs de 'omme vitesse e dans es plus le. De hie en le pose econde t donc 1/1.000 Ilya e rapi- r toute et que lisible utilisée le cette 1X rec- COMMISSION | Cg) Appendix to the INT. ARCHIVES OF PHOTOGRAMMETRY, Vol. XI4, 1956 Differences between Visual and Photographic Calibrations of Air Survey Cameras™ P. D. CARMAN AND H. BROWN, National Research Council, Ottawa, Canada SUMMARY : Significant differences have been found between the calibration of air survey cameras by visual means and their calibration by a photo- graphic procedure simulating conditions of use. The differences are chiefly of chromatic origin. uE logic of calibrating photogram- metric cameras by a photographic pro- cedure was accepted by the Seventh Inter- national Congress of Photogrammetry in 1952. However, visual methods have con- tinued in some use for reasons of tradition and of convenience of equipment. The Congress agreed that ‘‘a visual method will be permissible if it... gives the same values as the . . . photographic method to within the required accuracy.” Until the present, both formal and fortuitous com- parisons of the two methods have shown no discrepancies which significantly ex- ceeded the uncertainties of measurement including those arising from definition limitations in the cameras tested. During 1955, tests of Wild RCS5A cameras on the National Research Council of Canada’s new photographic calibrator were found to be showing consistent differ- ences from the visual calibration data furnished by the manufacturer. Both the calibrated focal length and the shape of the radial distortion curve showed small but persistent discrepancies. For cali- brated focal lengths, photographic values usually exceeded manufacturer's figures by .01 or .02 mm. Extreme values from the average radial measured distortion curves obtained photographically ranged from 10 to 17 microns, averaging 5 or 6 microns higher than the manufacturer's published data. The recognition of such small dis- crepancies was undoubtedly facilitated by the excellent definition of the Aviogon lens. A number of special measurements were made on two RCSA cameras to explore the effects of the spectral differences in- volved in the two calibration methods. These spectral differences are illustrated in Figure 1. Curve 4 shows the product 5E., that is the visibility function multi- plied, wave-length by wave-length, by the spectral energy curve for CIE illuminant "C" which is a standardized approxima- tion to daylight. This is reasonably repre- sentative of the source-receiver combina- tions used in visual calibrations. Curve B shows the product of photographic mean noon sunlight—that is the standard il- luminant for photography—the sensitivity of Aero Super XX emulsion, and the trans- mission of a Wratten 13 filter. This is a photographic approximation to the visual condition of calibration. Curve C shows the combination used in photographic calibration. It is the product of mean noon sunlight, the sensitivity of Aero Super XX emulsion, and the transmission of a Wratten minus blue filter. Results of the special measurements on the two cameras were essentially identical hence only one camera will be discussed here. Chromatic difference of distortion— also called chromatic difference of magni- fication or transverse colour—was meas- ured at a number of field angles. The slit of a large collimator was illuminated by various wave-lengths of monochromatic light from filtered gas discharge lamps and the corresponding image positions in the focal plane of the RC5A Aviogon lens were measured with a microscope. Results plotted in Figure 2 immediately confirm that calibration results will be likely to vary with changes in spectral character- istics of the calibrating system. To obtain further information on the * Contribution from the Division of Applied Physics, National Research Council, Ottawa, Canada. 623 )F | X

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