In a perspective projection, a circular target appears as an ellipse for an oblique view.
Herein, the ellipse center obtained from image coordinate measurement operators differs
from the projection of the circle center. This discrepancy is called eccentricity and may
lead to systematic errors. This article documents the significance of these discrepancies
and discusses five different correction methods that can be applied in the image space or
as a model adaptation. Two of the methods include the determination of the circle radius
and thus also offer a possibility to define the scale. The eccentricity correction procedures
are validated in a series of experiments, which proved that even extreme eccentricity
effects can be fully compensated. In the experiment on the approaches including scale
determination, the precision and accuracy of the scale definition is investigated, obtaining
relative accuracies of 0.5–1%.