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Diffstat (limited to 'dom/system/gonk/GeolocationUtil.cpp')
| -rw-r--r-- | dom/system/gonk/GeolocationUtil.cpp | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/dom/system/gonk/GeolocationUtil.cpp b/dom/system/gonk/GeolocationUtil.cpp new file mode 100644 index 000000000..99d484a19 --- /dev/null +++ b/dom/system/gonk/GeolocationUtil.cpp @@ -0,0 +1,28 @@ +/* -*- Mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 40 -*- */ +/* vim: set ts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this file, + * You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "GeolocationUtil.h" + +double CalculateDeltaInMeter(double aLat, double aLon, double aLastLat, double aLastLon) +{ + // Use spherical law of cosines to calculate difference + // Not quite as correct as the Haversine but simpler and cheaper + const double radsInDeg = M_PI / 180.0; + const double rNewLat = aLat * radsInDeg; + const double rNewLon = aLon * radsInDeg; + const double rOldLat = aLastLat * radsInDeg; + const double rOldLon = aLastLon * radsInDeg; + // WGS84 equatorial radius of earth = 6378137m + double cosDelta = (sin(rNewLat) * sin(rOldLat)) + + (cos(rNewLat) * cos(rOldLat) * cos(rOldLon - rNewLon)); + if (cosDelta > 1.0) { + cosDelta = 1.0; + } else if (cosDelta < -1.0) { + cosDelta = -1.0; + } + return acos(cosDelta) * 6378137; +} + |