[FredZarguna]

The model is highly exaggerated and actually has the most important effects removed. Latitude is responsible for the largest gravitational variation and the effect is greatest at the poles (5 parts in 1000) which this map does not show. The second largest effect is at altitude (~2/1000 over 8Km from mean sea level) which is also not shown. Local geological effects on gravity are <2 parts in 10,000, and that's all that appears here.

The local effect is so small that, depending on how massive a local geological feature is, your weight might actually be more seriously influenced by your location relative to the moon.

[reg45]

One of the major factors is the rotation of the earth. It causes the earth to bulge at the equator and also exerts an outward force on all objects - except at the poles, where the effect is zero.