Three-dimensional endoscopic measurements are made by adding an array of reference target points to the scene viewed by an 
endoscopic camera and characterizing the image formed by the camera when it views the scene from two or more viewing positions. Methods and apparatus are taught which allow one to make accurate measurements with any 
endoscope, without requiring any modification to the 
endoscope. Under certain circumstances, the measurements can be made without any pre-calibration of the 
endoscopic camera.A general measurement reference apparatus comprises a reference 
target array which is placed near to and fixed with respect to an object of interest inside an 
enclosure by means of a 
reference array holding apparatus and a 
reference array insertion apparatus. This measurement reference apparatus can be used to make either perspective dimensional measurements or to make conventional photogrammetric measurements of the object of interest.A general measurement apparatus to be used with the new methods comprises a reference 
target array which is placed near to and fixed with respect to an object of interest inside an 
enclosure by means of a 
reference array holding apparatus and a reference array 
insertion apparatus. In a version of this apparatus the reference array holding apparatus may attach the reference array directly to the object of interest and the combination may be inserted into the 
enclosure by the 
insertion apparatus. The general measurement apparatus also comprises an 
endoscopic camera located inside the enclosure. The camera is moved with respect to the object by a camera moving apparatus. Images formed by the camera are measured with an 
image measurement apparatus. These measurements are supplied to a computing apparatus which computes the desired three-dimensional distances. The measurement results are displayed to the user by a display apparatus.