A medical system comprising: a flexible device configured to be positioned at least partially within an anatomical passageway , the device including a plurality of sections (262, 264, and 266) and a shape sensor; and a memory device including computer executable instructions, the computer executable instructions comprising: instructions for determining a shape of the flexible device ; instructions for determining a set of candidate passageways based on the shape of the flexible device , wherein the set of candidate passageways includes the anatomical passageway ; instructions for determining a set of deformation forces for the plurality of sections (262, 264, and 266) of the flexible device ; instructions for determining that the flexible device is within the anatomical passageway based on modeling an effect of the set of deformation forces on the set of candidate passageways; and instructions for generating a composite model indicating a position of the flexible device relative to the anatomical passageway based on the shape of the flexible device , the set of deformation forces, and anatomical data describing the anatomical passageway . a flexible device configured to be positioned at least partially within an anatomical passageway , the device including a plurality of sections (262, 264, and 266) and a shape sensor; and a memory device including computer executable instructions, the computer executable instructions comprising: instructions for determining a shape of the flexible device ; instructions for determining a set of candidate passageways based on the shape of the flexible device , wherein the set of candidate passageways includes the anatomical passageway ; instructions for determining a set of deformation forces for the plurality of sections (262, 264, and 266) of the flexible device ; instructions for determining that the flexible device is within the anatomical passageway based on modeling an effect of the set of deformation forces on the set of candidate passageways; and instructions for generating a composite model indicating a position of the flexible device relative to the anatomical passageway based on the shape of the flexible device , the set of deformation forces, and anatomical data describing the anatomical passageway . instructions for determining a shape of the flexible device ; instructions for determining a set of candidate passageways based on the shape of the flexible device , wherein the set of candidate passageways includes the anatomical passageway ; instructions for determining a set of deformation forces for the plurality of sections (262, 264, and 266) of the flexible device ; instructions for determining that the flexible device is within the anatomical passageway based on modeling an effect of the set of deformation forces on the set of candidate passageways; and instructions for generating a composite model indicating a position of the flexible device relative to the anatomical passageway based on the shape of the flexible device , the set of deformation forces, and anatomical data describing the anatomical passageway . the shape of the flexible device , the set of deformation forces, and anatomical data describing the anatomical passageway . <EOS>