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// Example of using the GeographicLib::GravityCircle class
// This requires that the egm96 gravity model be installed; see
// https://geographiclib.sourceforge.io/C++/doc/gravity.html#gravityinst
#include <iostream>
#include <exception>
#include <GeographicLib/GravityModel.hpp>
#include <GeographicLib/GravityCircle.hpp>
using namespace std;
using namespace GeographicLib;
int main() {
try {
GravityModel grav("egm96");
double lat = 27.99, lon0 = 86.93, h = 8820; // Mt Everest
{
// Slow method of evaluating the values at several points on a circle of
// latitude.
for (int i = -5; i <= 5; ++i) {
double lon = lon0 + i * 0.2;
double gx, gy, gz;
grav.Gravity(lat, lon, h, gx, gy, gz);
cout << lon << " " << gx << " " << gy << " " << gz << "\n";
}
}
{
// Fast method of evaluating the values at several points on a circle of
// latitude using GravityCircle.
GravityCircle circ = grav.Circle(lat, h);
for (int i = -5; i <= 5; ++i) {
double lon = lon0 + i * 0.2;
double gx, gy, gz;
circ.Gravity(lon, gx, gy, gz);
cout << lon << " " << gx << " " << gy << " " << gz << "\n";
}
}
}
catch (const exception& e) {
cerr << "Caught exception: " << e.what() << "\n";
return 1;
}
}
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