c—M
COMMISSION. T H9
Appendix to the INT. ARCHIVES OF
| PHOTOGRAMMETRY, Vol. XIL:4, 1956
Communication to
VIII International Congress for Photogrammetry
Reprint from
Svensk Lantmateritidskrift
Congress Number 1956
Commission I
THE GRID METHOD AND THE Y-PARALLAX METHOD
FOR THE DETERMINATION OF SYSTEMATIC DISTUR-
DANCES IN AERIAL AND TERRESTRIAL PHOTOGRAPHS
D. Hallert
Stockholm 70
Introduction
In [5] a method has been given for the determination of some syste-
matic disturbances of aerial photographs, particularly the radial distor-
tion. This method is here called the grid method. Below, some results of
the practical application of this method will be given,
In [6] also another method for the determination of systematic dis-
turbances of aerial photographs was indicated. This latter method is
founded upon the measurements of y-parallaxes in approximately orien-
ted optical models of the pictures to be investigated. This method is here
called the y-parallax method. Below, the principles of this method will
be briefly described and some results of the practical application will
also be given. x-parallaxes can be treated similarly.
We assume a pair of approximately vertical aerial pictures with nor-
mal overlap and over comparatively flat ground to be approximately
oriented in a stereoscopic plotting instrument, in the simplest case a
mirror stereoscope. The y-parallaxes can be measured with high preci-
sion. À very simple method to measure the y-parallaxes is to place the
pictures upon each other and to determine the y-translations which are
necessary for coincidence between corresponding details in the pictures.
Temporarily we assume the y-parallaxes to be caused by the lacking
relative orientation and the radial distortion.
l. The location of the points for the y-parallax measurements
We preliminarily assume a pair of vertical aerial pictures exact-
ly oriented in a distortion-free stereoscopic plotter. This means that the
y-parallaxes in the usual six symmetrically located orientation points all
