Intended investigations in regard to the most suitable mathematical presentation of the decentering
distortion have just started in connection with project 4.
The participation at the Denver meeting of the Amerícan Society of Photogrammetry consisted in a
single session which covered subjects falling into the area of interest of all five projects.
PROJECT 2 (EFFECTS OF ENVIRONMENTAL CONDITIONS ON THE ELEMENTS OF INTERIOR ORIENTATION)
"Investigations will be conducted into the changes in focal length and distortion of
photogrammetric lenses and cameras due to the effects of environments. Where possible, controlled
environments will be simulated using operating cameras. Further tests under true aerial (or space)
conditions will be correlated. A primary purpose will be to keep aerial surveyors informed of test
results so that they can be informed of possible geometric errors.”
There has been little progress in this investigation since the Hamburg Congress. Some individual
studies that were planned have been delayed for various reasons.
Carman (National Research Council of Canada) has written a paper on vibration which will be
published this year in Photogrammetric Engineering and Remote Sensing. He reports on the vibrations
and their effects in terms of resolving power limitations on many combinations of aircraft, cameras
and camera mounts. Carman's data should be directly applicable to the work of many aerial surveyors.
Worton (Clyde Surveys, Great Britain) considers that the environmental effects of pressure, tem-
perature, temperature gradients, humidity and atmospheric refraction, which differ significantly from
that environment where camera calibration is performed, are a "final frontier" in the acquisition of
accurate photogrammetric data. These effects, he notes, are most serious at high altitudes. At lower
altitudes, the forward motion of the image during exposure time and the angular vibrations are most
degrading. Worton's paper (to be submitted to Commission I) emphasizes the practical problems faced by
the aerial surveyor in maintaining good resolution and accurate geometry. These include the extra
weight and complexity of gyro-stabilized camera platforms, the instability of aircraft at low alti-
tudes, the inability to control temperature gradients in the camera such that there is no possibility
of an equilibrium condition. When such problems have been solved, there is still the problem of
"seeing" through the ever increasing pollution which is found in every region of our finite globe.
Many cameras are subjected to temperatures as cold as -309c during high altitude surveying, and
Meier (1978), Bormann (1980) and Norton (1980 a,b) have shown that the distortion of lenses and cam-
eras changes significantly for this environment. It is suggested that those surveyors who operate
under similar conditions - anything lower than -20? - monitor the temperature of their camera at five
or more points (filters, outer lens, inner lens, focal plane, platen, etc) to determine from published
data the magnitude of change in distortion. This group would appreciate being informed of any such
test and would be glad to assist in establishing the possible magnitude of geometric changes.
PROJECT 3 (STABILITY OF PHOTOGRAMMETRIC LENSES) —
"Juhani Hakkarainen suggests to evaluate data from repeated calibrations .of the same cameras in
view of changes of the calibrated focal length, symmetrical radial lens distortion, decentering A =
distortion, distances between fiducial marks, and resolving power. He will carry out annual
calibrations of all cameras available in Finland until 1984 and asks for contributions from other
institutions such as the National Research Council of Canada, the United States Geological Survey and
the camera manufacturers. It is hoped that NRC calibration plates for-a larger number of cameras
calibrated in 10 successive years can be located in storage and remeasured to provide most of the
desired data. An attempt will be made to include those lenses known to have changed.”
The following report was prepared without the benefit of Prof. Dr. Hakkarainen's contribution and,
therefore, covers only the work carried out at the National Research Council of Canada. Camera used in
mapping contracts for the Canadian federal government had to be calibrated annually in the past. The
introduction of longer periods between calibrations is imminent. The present NRC facility has been in -
operation since November of 1973. It provides for one bank of collimators spaced at (45/16)? to
maximum field angle of 59.0625°. Two exposures are taken along the two diagonals of the format area of
a camera. Since only every second collimator is measured as part of the standard calibration
procedure, it was decided to remeasure all plates of interest for this investigation reading all
available images. Of the 636 plates taken until the end of February 1982, 226 were selected for
remeasurement. These plates constitute series of from six to ten plates for lenses of the following
types: Wild Aviogon 153/5.6 (3), Wild Universal-Aviogon 153/5.6 (5 for RC8's and 5 for RC10's), Wild
Universal-Aviogon I 153/5.6 (1), Wild Universal-Aviogon 153/4 (3), Wild Super-Aviogon II 88/5.6 (4),
Zeiss Pleogon A 153/5.6 (2), Zeiss Pleogon A2 153/5.6 (4), Zeiss Pleogon A2 153/4 (2) and Zeiss Super-
Pleogon A2 85/4 (2). The numbers in brackets indicate the number of selected series of lens/filter
combinations for each lens types. To the end of February, 164 plates had been measured, but none of
the measurements had been processed beyond initial data checking. No series of at least five plates
were available for other lens types.
The present NRC facility does not include resolving power targets in the collinator targets and
does not, therefore, provide for a routine check of resolution as part of a calibration. NRC cannot,
therefore, contribute resoluting power data to the investigation.
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