https://www.zcyphygeodesy.com/en/h-nd-116.html
From four basic parameters of the Earth ellipsoid, calculate the main geometric and physical derived constants of the Earth ellipsoid. The fourth basic parameter can be selected from the second-degree zonal harmonic coefficient C̅₂₀ from global geopotential model, dynamic form factor J₂, reciprocal 1/f of the ellipsoid flattening and ellipsoid normal geopotential U₀.
PAGravf4.5 suggests that the scale parameters (GM, a) of global geopotential model, second-degree zonal harmonic coefficient C̅₂₀ and the mean rotation angular velocity ω should be employed as the four basic parameters of the normal ellipsoid. Using such a normal ellipsoid as the reference datum, the second-degree zonal harmonic term of anomalous gravity field is always zero, which is beneficial to improve the performance of the gravity field approach.
EllipsoidconstCalc.f90
Given the dynamic form factor J2 in the test program.
Output all the geometric and physical constants of the Earth ellipsoid on the computer scree, which include:
Geocentric gravitational constant GM(e14m2/s2) of the Earth
Mean angular velocity w(e-5/s) of the Earth
Major semi axis a(m) of the Earth
Dynamic form factor J2(e-3)
Geopotential coefficient c20(e-3) from GM
Reciprocal 1/f of ellipsoid flattening
Normal ellipsoid geopotential U0=WG
Minor semi axis of the Earth b(m)
Radius of sphere of same volume R(m)
Linear eccentricity E(m)
Square of first eccentricity e2
Square of second eccentricity e21
Equatorial curvature radius M(m)
Polar radius of curvature c(m)
Gravity flattening reciprocal 1/fk
Geodetic parameter m
Normal gravity at equator ga(m/s2)
Normal gravity at pole gp(m/s2)
ELLIPSOIDPARA(GRS)
Input parameters: GRS(1), GRS(2), GRS(4) and one of GRS(3), GRS(5), GRS(6).
GRS(1) - Geocentric gravitational constant GM.
GRS(2) - Major semi axis of the Earth.
GRS(3)- Dynamic form factor.
GRS(4)- Mean angular velocity omega (e-5/s) of the Earth.
GRS(5)- ellipsoid flattening f.
GRS(6)- Normal ellipsoid geopotential.
Return parameters: GRS(1:6)
Normalconst(GRS,BLH,NFD)
Input：BLH(3)-Latitude, longitude (degree decimal) and ellipsoidal height (m) of the calculation point
Return parameters: NFD(1)- the normal gravity potential. NFD(2)- normal gravity.
normdjn(GRS, djn)
LegPn_dt2(pn,dp1,dp2,n,t) ! t=cos ψ
BLH_RLAT(GRS,BLH,RLAT)
Fortran90, 132 Columns fixed format. Fortran compiler for any operating system. No external link library required.
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