Detailed gravity anomalies derived from SEASAT altimeter data : a comparison of two alternative approaches: least squares collocation and a method based on FFT / R.H.N. HaagmansGOCE : ESA's gravity mission / [prepared by: Roger Haagmans, Rune Floberghagen, Bernd Pieper ; ed.: Honora Rider ... et al. ; ill.: AOES Medialab]Swarm : ESA's magnetic field mission / [authors R. Haagmans, R. Bock, H. Rider ; prod. ed. K. Fletcher]