We had used height anomaly to solve the mixed boundary value problem by measuring the value of gravity of standpoint, level coordinate and height.

In January 2009, bilateral trade value dropped 21.6% year on year. The gravity and speed of the decline are unprecedented indeed.

In Xi 'an area, because the groundwater has excessively been exploited, the press-dense effect of strata appears so that the ground subsides and the gravity value increases sharply.