Final answer:
The rate of increase of the Earth's gravity field is greater at latitude 60° than at latitude 30°.
Step-by-step explanation:
The rate of increase of the Earth's gravity field at latitudes 30° and 60° can be determined using the formula:
gravity at latitude 30° / gravity at latitude 60° = cos(latitude 60°) / cos(latitude 30°)
Since the Earth is not a perfect sphere and experiences bulging at the equator due to its rotation, the strength of gravity is greater at the poles compared to the equator. Therefore, the gravity field at latitude 60° would have a greater rate of increase compared to latitude 30°.