Which pair correctly identifies the two primary categories of gravity measurements?

• A. Absolute and Relative
• B. Observed and Normal
• C. Bouguer and Free-air
• D. Gravitational and Centrifugal

Answer: (A)

Gravity measurements come in two main approaches: absolute gravity and relative gravity. Absolute gravity uses an absolute gravimeter to measure the actual local acceleration due to gravity at a point, giving a true value of g in standard units. This provides a point-specific, independent measure of gravity that helps anchor the gravity field and geoid models. Relative gravity uses a relative gravimeter to compare gravity between two locations or to monitor changes over time, yielding differences in gravity rather than an absolute value. This is especially useful for mapping gravity anomalies across a network or watching for temporal mass changes. The other terms describe corrections or different physical components and aren’t the standard way we categorize gravity measurements.