Spurred by a tremendous increase in new and highly accurate data and by prospects for further improvements, theoretical studies in geodesy have concentrated on devising new methods, or adapting extradisciplinary ones, to process the data efficiently and accurately. Satellite altimetry, the NAVSTAR Global Positioning System, satellite Doppler, satellite‐to‐satellite tracking, satellite laser, VLBI, satellite interferometry, and inertial navigation advancements are all contributing to provide the geodetic, and indeed the geophysical, community with a wealth of new data. Least‐squares collocation has achieved prominence through numerous applications, but for efficiency it must compete with other methods, such as those founded in spectral theory. Also, the improved measurement accuracy has mandated the development of more realistic geodetic models where former approximations can no longer be tolerated.