GeographicLib: GeographicLib::GravityCircle Class Reference (original) (raw)

Gravity on a circle of latitude. More...

#include <[GeographicLib/GravityCircle.hpp](GravityCircle%5F8hpp%5Fsource.html)>

Gravity on a circle of latitude.

Evaluate the earth's gravity field on a circle of constant height and latitude. This uses a CircularEngine to pre-evaluate the inner sum of the spherical harmonic sum, allowing the values of the field at several different longitudes to be evaluated rapidly.

Use GravityModel::Circle to create a GravityCircle object. (The constructor for this class is private.)

See Geoid heights on a multi-processor system for an example of using GravityCircle (together with OpenMP) to speed up the computation of geoid heights.

Example of use:

#include

#include

using namespace std;

try {

double lat = 27.99, lon0 = 86.93, h = 8820;

{

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";

}

}

{

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;

}

}

int main(int argc, const char *const argv[])

Header for GeographicLib::GravityCircle class.

Header for GeographicLib::GravityModel class.

Gravity on a circle of latitude.

Math::real Gravity(real lon, real &gx, real &gy, real &gz) const

Model of the earth's gravity field.

Namespace for GeographicLib.

Gravity is a command-line utility providing access to the functionality of GravityModel and GravityCircle.

Definition at line 41 of file GravityCircle.hpp.

◆ Gravity()

Evaluate the gravity.

Parameters

Returns

W the sum of the gravitational and centrifugal potentials (m2 s−2).

The function includes the effects of the earth's rotation.

Definition at line 51 of file GravityCircle.cpp.

◆ Disturbance()

Evaluate the gravity disturbance vector.

Parameters

Returns

T the corresponding disturbing potential (m2 s−2).

Definition at line 61 of file GravityCircle.cpp.

◆ GeoidHeight()

Evaluate the geoid height.

Parameters

Returns

N the height of the geoid above the reference ellipsoid (meters).

Some approximations are made in computing the geoid height so that the results of the NGA codes are reproduced accurately. Details are given in Details of the geoid height and anomaly calculations.

Definition at line 71 of file GravityCircle.cpp.

◆ SphericalAnomaly()

Evaluate the components of the gravity anomaly vector using the spherical approximation.

Parameters

The spherical approximation (see Heiskanen and Moritz, Sec 2-14) is used so that the results of the NGA codes are reproduced accurately. approximations used here. Details are given in Details of the geoid height and anomaly calculations.

Definition at line 81 of file GravityCircle.cpp.

◆ W()

Evaluate the components of the acceleration due to gravity and the centrifugal acceleration in geocentric coordinates.

Parameters

Returns

W = V + Φ the sum of the gravitational and centrifugal potentials (m2 s−2).

Definition at line 166 of file GravityCircle.hpp.

◆ V()

Evaluate the components of the acceleration due to gravity in geocentric coordinates.

Parameters

Returns

V = W - Φ the gravitational potential (m2 s−2).

Definition at line 186 of file GravityCircle.hpp.

◆ T() [1/2]

Evaluate the components of the gravity disturbance in geocentric coordinates.

Parameters

Returns

T = W - U the disturbing potential (also called the anomalous potential) (m2 s−2).

Definition at line 206 of file GravityCircle.hpp.

◆ T() [2/2]

Evaluate disturbing potential in geocentric coordinates.

Parameters

Returns

T = W - U the disturbing potential (also called the anomalous potential) (m2 s−2).

Definition at line 220 of file GravityCircle.hpp.

◆ Init()

◆ EquatorialRadius()

Returns

a the equatorial radius of the ellipsoid (meters). This is the value inherited from the GravityModel object used in the constructor.

Definition at line 241 of file GravityCircle.hpp.

◆ Flattening()

Returns

f the flattening of the ellipsoid. This is the value inherited from the GravityModel object used in the constructor.

Definition at line 248 of file GravityCircle.hpp.

◆ Latitude()

◆ Height()

◆ Capabilities() [1/2]

Returns

caps the computational capabilities that this object was constructed with.

Definition at line 267 of file GravityCircle.hpp.

◆ Capabilities() [2/2]

◆ GravityModel

The documentation for this class was generated from the following files:

• GravityCircle.hpp
• GravityCircle.cpp