Variation with Latitude:

Earth is not a perfect sphere; it is an oblate spheroid, meaning it is slightly flattened at the poles and bulging at the equator. Gravity is stronger at the poles and weaker at the equator because: The poles are closer to the Earth's center (smaller radius, stronger gravitational pull). The equator experiences a greater outward centrifugal force due to Earth's rotation.

Constants :

Incorporate Earth's flattening and the effects of rotation.

SI system is absolute (gravitationally independent) as: Mass - in relation with Planck constant Time - in terms of vibration of isotope of Cesium Length - in terms of distance covered by Light All of which are independent of effect of gravity