1. A measurement apparatus for measuring relative position or orientation of an image-capturing apparatus adapted to capture images of one or more measurement objects with respect to a measurement object, wherein the measurement apparatus comprises: an image acquiring unit configured to acquire a captured image from the image-capturing apparatus; a projection unit configured to project geometric features of a 3D model of the measurement object onto the captured image based on a position and orientation of the image-capturing apparatus to obtain projection geometric features; a selecting unit configured to select projection geometric features to be used in calculation of the position or orientation from the projection geometric features obtained by the projection unit based on distances with respect to the projection geometric features in the captured image; and a calculating unit configured to calculate the relative position or orientation of the image-capturing apparatus with respect to the measurement object using the projection geometric features selected by the selecting unit and image geometric features corresponding to the selected projection geometric features detected in the captured image.