In the Commentary 'ψ in the sky' (Nature Physics 11, 615–617; 2015), the resolution of GOCE in Fig. 1 was misleading. The spatial resolution of GOCE is application specific, and in fact can reach less than 100 km for a recovery error of the geoid of 2 cm. This has now been clarified in the online versions after print 20 October 2015.