earth_models.py

import enum

from dataclasses import dataclass

class EarthModel(enum.Enum):
    WGS84 = "WGS84"
    GRS80 = "GRS80"


@dataclass
class WGS84:
    # https://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/egm08_wgs84.html
    # https://duckduckgo.com/?q=wgs84+constants&ia=web
    a: float = 6378137.0  # m
    b: float = 6356752.3142451794975639665996337  # 6356752.31424518 # m
    earth_flat_coef: float = 1.0 / ((a - b) / a)  # 298.257223563
    e2: float = 2.0 / earth_flat_coef - 1.0 / (earth_flat_coef * earth_flat_coef)
    e2inv: float = 1 - e2
    ep2: float = e2 / (1 - e2)


@dataclass
class GRS80:
    a = 6378137  # m
    b = 6356752.314140  # m
    earth_flat_coef = 1.0 / ((a - b) / a)  # 298.257222101
    e2 = 2.0 / earth_flat_coef - 1.0 / (earth_flat_coef * earth_flat_coef)
    ep2 = e2 / (1 - e2)