@techreport{TR-IC-98-08,
  number = {IC-98-08},
  author = {Marcus Vinícius A. Andrade and Jorge Stolfi},
  title = {Exact Algorithms for Circles on the Sphere},
  month = {April},
  year = {1998}, 
  institution = {Institute of Computing, University of Campinas},
  note = {In English, 16 pages.
    \par\selectlanguage{english}\textbf{Abstract}
      We develop exact algorithms for geometric operations on
      general circles and circular arcs on the sphere, using integer
      homogeneous coordinates.  The algorithms include testing a point
      against a circle, computing the intersection of two circles, and
      ordering three arcs out of the same point. These operations allow
      robust manipulation of maps on the sphere, providing a reliable
      framework for GIS, robotics, and other geometric applications.
    \par
      (This paper will be presented at the ACM Symposium on
      Computational Geometry, Minneapolis, June 07-10, 1998.)
  }
}