Determine the three components of the gravity vector at a single point.

## Usage

value = MakeGravGridPoint (cilm, gm, r0, r, lat, lon, [lmax, omega, dealloc])


## Returns

value : float, dimension (3)
Vector components (r, theta, phi) of the gravity at (r, lat, lon).

## Parameters

cilm : float, dimension (2, lmaxin+1, lmaxin+1)
The real 4-pi normalized spherical harmonic coefficients of the gravitational potential. The coefficients C0lm and C1lm refer to the cosine (Clm) and sine (Slm) coefficients, respectively, with Clm=cilm[0,1,m] and Slm=cilm[1,l,m].
gm : float
The gravitational constant multiplied by the mass of the planet.
r0: float
The reference radius of the spherical harmonic coefficients.
r: float
The radius to evaluate the gravity field.
lat : float
The latitude of the point in degrees.
lon : float
The longitude of the point in degrees.
lmax : optional, integer, default = lmaxin
The maximum spherical harmonic degree used in evaluating the function.
omega : optional, float, default = 0
The angular rotation rate of the planet.
dealloc : optional, integer, default = 0
0 (default) = Save variables used in the external Legendre function calls. (1) Deallocate this memory at the end of the funcion call.

## Description

MakeGravGridPoint will compute the three components of the gravity vector (gravitational force + centrifugal force) at a single point. The input latitude and longitude are in degrees, and the output components of the gravity are in spherical coordinates (r, theta, phi). The gravitational potential is given by

V = GM/r Sum_{l=0}^lmax (r0/r)^l Sum_{m=-l}^l C_{lm} Y_{lm},

and the gravitational acceleration is

B = Grad V.

The coefficients are referenced to a radius r0, and the output accelerations are in m/s^2. To convert m/s^2 to mGals, multiply by 10^5. If the optional angular rotation rate omega is specified, the gravity vector will be calculated in a body-fixed rotating reference frame and will include the contribution of the centrifugal force.

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