In a perspective projection, a circular target appears as an ellipse for an oblique view. The ellipse center as a result of the image coordinate measurement differs from the projection of the circle center. This discrepancy is called eccentricity and may lead to systematic errors. This contribution discusses four different correction methods that can be applied on the observation or the model side. The last method includes the determination of the circle radius and thus also offers a possibility to defi ne the scale. The correction procedures are applied in an experiment with high eccentricities where the remaining error is signifi cantly reduced. In another experiment, the precision and accuracy of the scale defi nition is investigated.