This paper presents a novel method for detecting scale
invariant keypoints. It fills a gap in the set of available
methods, as it proposes a scale-selection mechanism for
junction-type features. The method is a scale-space extension
of the detector proposed by F¨orstner (1994) and uses
the general spiral feature model of Big¨un (1990) to unify
different types of features within the same framework. By
locally optimising the consistency of image regions with respect
to the spiral model, we are able to detect and classify
image structures with complementary properties over scalespace,
especially star and circular shapes as interpretable
and identifiable subclasses. Our motivation comes from
calibrating images of structured scenes with poor texture,
where blob detectors alone cannot find sufficiently many
keypoints, while existing corner detectors fail due to the
lack of scale invariance. The procedure can be controlled
by semantically clear parameters. One obtains a set ...