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Simplify angleBetween to avoid cancellation losses

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Michael Krasnyk 2017-05-16 17:45:07 +02:00 committed by Patrick Niklaus
parent c535e74a65
commit 7a4c5a64fa
2 changed files with 24 additions and 9 deletions
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10
include/util/bearing.hpp
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@ -120,15 +120,7 @@ inline double reverse(const double bearing)
// entry_bearing of 0. // entry_bearing of 0.
inline double angleBetween(const double entry_bearing, const double exit_bearing) inline double angleBetween(const double entry_bearing, const double exit_bearing)
{ {
// transform bearing from cw into ccw order return std::fmod(entry_bearing - exit_bearing + 540., 360.);
const double offset = 360 - entry_bearing;
const double rotated_exit = [](double bearing, const double offset) {
bearing += offset;
return bearing > 360 ? bearing - 360 : bearing;
}(exit_bearing, offset);
const auto angle = 540 - rotated_exit;
return angle >= 360 ? angle - 360 : angle;
} }
} // namespace bearing } // namespace bearing

23
unit_tests/util/bearing.cpp
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@ -51,6 +51,29 @@ BOOST_AUTO_TEST_CASE(bearing_angle_test)
{ {
BOOST_CHECK_EQUAL(bearing::angleBetween(257.78421507794314, 77.784215077943117), 0.); BOOST_CHECK_EQUAL(bearing::angleBetween(257.78421507794314, 77.784215077943117), 0.);
BOOST_CHECK_EQUAL(bearing::angleBetween(77.784215077943117, 257.78421507794314), 0.); BOOST_CHECK_EQUAL(bearing::angleBetween(77.784215077943117, 257.78421507794314), 0.);
// Check quadrants
BOOST_CHECK_EQUAL(bearing::angleBetween(45., 45.), 180.);
BOOST_CHECK_EQUAL(bearing::angleBetween(45., 315.), 270.);
BOOST_CHECK_EQUAL(bearing::angleBetween(45., 225.), 0.);
BOOST_CHECK_EQUAL(bearing::angleBetween(45., 135.), 90.);
BOOST_CHECK_EQUAL(bearing::angleBetween(45., 90.), 135.);
// Check edge cases
BOOST_CHECK_EQUAL(bearing::angleBetween(0., 360.), 180.);
BOOST_CHECK_EQUAL(bearing::angleBetween(360., 0.), 180.);
BOOST_CHECK_EQUAL(bearing::angleBetween(0., 0.), 180.);
BOOST_CHECK_EQUAL(bearing::angleBetween(360., 360.), 180.);
BOOST_CHECK_EQUAL(bearing::angleBetween(0., 180.), 0.);
BOOST_CHECK_EQUAL(bearing::angleBetween(360., 180.), 0.);
BOOST_CHECK_EQUAL(bearing::angleBetween(180., 0.), 0.);
BOOST_CHECK_EQUAL(bearing::angleBetween(180., 360.), 0.);
BOOST_CHECK_EQUAL(bearing::angleBetween(90., 270.01), 359.99);
// 5 digits loss due to cancellation in 90+180-269.99
BOOST_CHECK_CLOSE(bearing::angleBetween(90., 269.99), 0.01, 1e-10);
} }
BOOST_AUTO_TEST_SUITE_END() BOOST_AUTO_TEST_SUITE_END()