A medical apparatus (100, 300, 400) comprising: - a subject support for receiving a subject, - a camera configured for imaging the support surface.; - the subject support and the camera being movable relative to one another along a linear path between a first position, an intermediate position and a second position, wherein each of one or more intermediate positions is located between the first position and the second position; wherein - the medical apparatus is configured for measuring the subject support's and the camera's displacement along the linear path between the first position and the at least one intermediate position, - a memory containing machine executable instructions; - a processor for controlling the medical apparatus, wherein execution of the machine executable instructions cause the processor to: - acquire an initial image with the camera when the subject support and/or the camera are in the first position relative to one another; - control the subject support to move at least one of the subject support and the camera from the first position to the second position relative to one another; - acquire at least one intermediate image with the camera - measure the subject support and camera's displacement for each of the at least one intermediate image as at least one of the subject support and the camera are moved from the first position to the second position; and - calculate a height profile (150, 600, 604) of the subject by comparing the initial image and the at least one intermediate image, wherein the height profile is at least partially calculated using the displacement, wherein the height profile is descriptive of the spatially dependent height of the subject above the support surface. - a subject support for receiving a subject, - a camera configured for imaging the support surface.; - the subject support and the camera being movable relative to one another along a linear path between a first position, an intermediate position and a second position, wherein each of one or more intermediate positions is located between the first position and the second position; wherein - the medical apparatus is configured for measuring the subject support's and the camera's displacement along the linear path between the first position and the at least one intermediate position, - a memory containing machine executable instructions; - a processor for controlling the medical apparatus, wherein execution of the machine executable instructions cause the processor to: - acquire an initial image with the camera when the subject support and/or the camera are in the first position relative to one another; - control the subject support to move at least one of the subject support and the camera from the first position to the second position relative to one another; - acquire at least one intermediate image with the camera - measure the subject support and camera's displacement for each of the at least one intermediate image as at least one of the subject support and the camera are moved from the first position to the second position; and - calculate a height profile (150, 600, 604) of the subject by comparing the initial image and the at least one intermediate image, wherein the height profile is at least partially calculated using the displacement, wherein the height profile is descriptive of the spatially dependent height of the subject above the support surface. - acquire an initial image with the camera when the subject support and/or the camera are in the first position relative to one another; - control the subject support to move at least one of the subject support and the camera from the first position to the second position relative to one another; - acquire at least one intermediate image with the camera - measure the subject support and camera's displacement for each of the at least one intermediate image as at least one of the subject support and the camera are moved from the first position to the second position; and - calculate a height profile (150, 600, 604) of the subject by comparing the initial image and the at least one intermediate image, wherein the height profile is at least partially calculated using the displacement, wherein the height profile is descriptive of the spatially dependent height of the subject above the support surface.