Step 1: Understand the need.
The work involves big scientific studies like the earth's magnetic field and the direction of continental drift over very large areas.
Step 2: Recall what such studies demand.
Large-area, high-precision work must allow for the curved shape of the earth.
Step 3: Remove the small-area surveys.
Cadastral surveying deals with property boundaries and topographical surveying with local ground features, both over small areas.
Step 4: Check aerial surveying.
Aerial surveying maps the ground from photographs but is not the class meant for these earth-scale scientific studies.
Step 5: Identify the correct type.
Geodetic surveying accounts for the earth's curvature, covers huge areas with great accuracy, and is used for such scientific work.
Step 6: State the answer.
Hence the method is geodetic surveying.
\[ \boxed{\text{Geodetic surveying}} \]