gecko-dev/dom/system/gonk/GeolocationUtil.cpp

29 lines
1.1 KiB
C++

/* -*- 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;
}