A Discussion on the measurement and interpretation of changes of strain in the Earth - Useful geodetic measurements with radio interferometers?

Gold pointed out in 1967 that as some quasars have components smaller than 0.01, radio interferometers might allow distances on Earth of the order of 104 km to be measured to a precision of a few centimetres. He envisaged radio interferometers employing video tape recorders and atomic time standards. The difficulties and probable costs of such measurements are reviewed.