A processor-implemented method on a user equipment, UE, comprising a camera, the method comprising: generating, based in part on an estimated camera pose for a current image frame (255; T ), a first map comprising local features ( f 1 , f 2 , f 3 , f 4 , p 1 , p 2 ) and 3D locations of the local features, wherein the local features comprise a plurality of visible features ( f 1 , f 2 , f 3 , f 4 ) in the current image frame and a set of covisible features ( f 2 , f 3 , f 4 , p 1 , p 2 ) corresponding to the plurality of visible features, wherein for each visible feature fi in the current image frame a corresponding set of covisible features C i is determined as those features visible from all prior camera poses from which the feature fi is also visible, and the set of covisible features C is obtained as the union of sets of covisible features C i corresponding to the local features f i ; determining a second map for a prior image frame (260, T-1 ) at the prior camera pose comprising prior features ( f 2 , f 3 , f 4 , p 1 , p 2 ) and 3D locations corresponding to the prior features, wherein each prior feature was first imaged at a time prior to the first imaging of any ( f 1 ) of the local features, and wherein each prior feature is within a threshold distance of at least one local feature; determining, based on a comparison of the first map to the second map, a first subset ( f 2 , f 3 , f 4 , p 1 , p 2 ) comprising previously imaged local features in the first map and a corresponding second subset ( f 2 , f 3 , f 4 , p 1 , p 2 ) of the prior features in the second map, wherein each local feature in the first subset corresponds to a distinct prior feature in the second subset; and determining a transformation, wherein the transformation maps the first subset of the local features to the second subset of the prior features. generating, based in part on an estimated camera pose for a current image frame (255; T ), a first map comprising local features ( f 1 , f 2 , f 3 , f 4 , p 1 , p 2 ) and 3D locations of the local features, wherein the local features comprise a plurality of visible features ( f 1 , f 2 , f 3 , f 4 ) in the current image frame and a set of covisible features ( f 2 , f 3 , f 4 , p 1 , p 2 ) corresponding to the plurality of visible features, wherein for each visible feature fi in the current image frame a corresponding set of covisible features C i is determined as those features visible from all prior camera poses from which the feature fi is also visible, and the set of covisible features C is obtained as the union of sets of covisible features C i corresponding to the local features f i ; determining a second map for a prior image frame (260, T-1 ) at the prior camera pose comprising prior features ( f 2 , f 3 , f 4 , p 1 , p 2 ) and 3D locations corresponding to the prior features, wherein each prior feature was first imaged at a time prior to the first imaging of any ( f 1 ) of the local features, and wherein each prior feature is within a threshold distance of at least one local feature; determining, based on a comparison of the first map to the second map, a first subset ( f 2 , f 3 , f 4 , p 1 , p 2 ) comprising previously imaged local features in the first map and a corresponding second subset ( f 2 , f 3 , f 4 , p 1 , p 2 ) of the prior features in the second map, wherein each local feature in the first subset corresponds to a distinct prior feature in the second subset; and determining a transformation, wherein the transformation maps the first subset of the local features to the second subset of the prior features. <EOS>