We consider Calderón’s inverse problem with partial data in dimensions
. If the
inaccessible part of the boundary satisfies a (conformal) flatness condition in one
direction, we show that this problem reduces to the invertibility of a broken geodesic
ray transform. In Euclidean space, sets satisfying the flatness condition include parts
of cylindrical sets, conical sets, and surfaces of revolution. We prove local uniqueness
in the Calderón problem with partial data in admissible geometries, and global
uniqueness under an additional concavity assumption. This work unifies two earlier
approaches to this problem—one by Kenig, Sjöstrand, and Uhlmann, the other by
Isakov—and extends both. The proofs are based on improved Carleman
estimates with boundary terms, complex geometrical optics solutions involving
reflected Gaussian beam quasimodes, and invertibility of (broken) geodesic ray
transforms. This last topic raises questions of independent interest in integral
geometry.