@inproceedings{and-sto-98-circ,
  author = {Marcus Vin{\'\i}cius A. Andrade and Jorge Stolfi},
  title = {Exact Algorithms for Circles on the Sphere},
  booktitle = {Proceedings of the 14th ACM Symposium on Computational Geometry},
  location = {Minneapolis, MN},
  pages = {126--134},
  year = 1998,
  month = jun,
  doi = {10.1145/276884.276898},
  isbn = {0-89791-973-4},
  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.}
}