Model-Based Detection and Localization of Circular Landmarksin Aerial Images

  • Authors:
  • Christian Drewniok;Karl Rohr

  • Affiliations:
  • Fachbereich Informatik, Universität Hamburg, Vogt-Kölln-Straße 30, D-22527 Hamburg, Germany. E-mail: drewniok@informatik.uni-hamburg.de, rohr@informatik.uni-hamburg.de;Fachbereich Informatik, Universität Hamburg, Vogt-Kölln-Straße 30, D-22527 Hamburg, Germany. E-mail: drewniok@informatik.uni-hamburg.de, rohr@informatik.uni-hamburg.de

  • Venue:
  • International Journal of Computer Vision
  • Year:
  • 1997

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Abstract

The photogrammetric exploitation of aerial images essentiallyrequires the accurate reconstruction of the imaging geometry. Thisespecially includes the determination of the orientation of thecamera. Usually, the orientation parameters are determined byspatial resection, knowing the exact coordinates of control points onthe ground and in the image. The reliability and accuracy of thisregistration task strongly depend on the selection of suitablelandmarks as well as on the precision obtained for landmarklocalization. In this contribution, we consider the problem ofautomatic landmark extraction for the purpose of aerial imageregistration. We suggest to use manhole covers as a specific type ofcircular landmarks which frequently occur in urban environments andwe introduce a model-based approach for localizing these featureswith high subpixel precision.Our approach is based on a parametric intensity model. Localizationof the landmarks is done by directly fitting this modelto the observed image intensities. Since we have an explicitdescription of the landmark it is possible to verify the result byexploiting the estimated parameters. We also address the problem oflandmark detection which can greatly be supported by templatematching. The template used is a prototype model which isgenerated from representative examples during a training phase. Thetraining scheme also provides initial values for the fittingprocedure as well as thresholds for the final verification step. Thefull approach has been tested on synthetic as well as on real imagedata.