ontent">
   Affinely adapted features.
  </span>
 </div>
</div>

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<h1 id="tut.covdet.ori">Feature orientation</h1>
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<p>The detection methods discussed so far are rotationally
invariant. This means that they detect the same circular or elliptical
regions regardless of an image rotation, but they do not allow to fix
and normalise rotation in the feature frame. Instead, f