if all of the Earth topography, mountains
and valleys were scoured off leaving a continuous
world's ocean completely at rest, without
the effects of currents, weather and tides.
The effect of the Earth's gravity on this
hypothetical world mean sea level is represented
by the geoid. However, because the Earth's
gravity is not equal in all places, this
hypothetical ocean is not perfectly smooth.
The strength of the Earths' gravity, and
consequent effect on the shape of the geoid
is represented by color variations in this
on the image to see another example.