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29 lines
1.1 KiB
C++
29 lines
1.1 KiB
C++
/* -*- Mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 40 -*- */
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/* vim: set ts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "GeolocationUtil.h"
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double CalculateDeltaInMeter(double aLat, double aLon, double aLastLat, double aLastLon)
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{
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// Use spherical law of cosines to calculate difference
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// Not quite as correct as the Haversine but simpler and cheaper
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const double radsInDeg = M_PI / 180.0;
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const double rNewLat = aLat * radsInDeg;
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const double rNewLon = aLon * radsInDeg;
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const double rOldLat = aLastLat * radsInDeg;
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const double rOldLon = aLastLon * radsInDeg;
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// WGS84 equatorial radius of earth = 6378137m
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double cosDelta = (sin(rNewLat) * sin(rOldLat)) +
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(cos(rNewLat) * cos(rOldLat) * cos(rOldLon - rNewLon));
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if (cosDelta > 1.0) {
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cosDelta = 1.0;
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} else if (cosDelta < -1.0) {
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cosDelta = -1.0;
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}
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return acos(cosDelta) * 6378137;
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}
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