PerformanceAwareProgramming/part2/listing_0065_haversine_formula.cpp

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2023-06-25 12:30:56 +00:00
/* ========================================================================
(C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Please see https://computerenhance.com for more information
======================================================================== */
/* ========================================================================
LISTING 65
======================================================================== */
static f64 Square(f64 A)
{
f64 Result = (A*A);
return Result;
}
static f64 RadiansFromDegrees(f64 Degrees)
{
f64 Result = 0.01745329251994329577 * Degrees;
return Result;
}
// NOTE(casey): EarthRadius is generally expected to be 6372.8
static f64 ReferenceHaversine(f64 X0, f64 Y0, f64 X1, f64 Y1, f64 EarthRadius)
{
/* NOTE(casey): This is not meant to be a "good" way to calculate the Haversine distance.
Instead, it attempts to follow, as closely as possible, the formula used in the real-world
question on which these homework exercises are loosely based.
*/
f64 lat1 = Y0;
f64 lat2 = Y1;
f64 lon1 = X0;
f64 lon2 = X1;
f64 dLat = RadiansFromDegrees(lat2 - lat1);
f64 dLon = RadiansFromDegrees(lon2 - lon1);
lat1 = RadiansFromDegrees(lat1);
lat2 = RadiansFromDegrees(lat2);
f64 a = Square(sin(dLat/2.0)) + cos(lat1)*cos(lat2)*Square(sin(dLon/2));
f64 c = 2.0*asin(sqrt(a));
f64 Result = EarthRadius * c;
return Result;
}