In recent years, various kinds of endoscope have been developed and widely used to endoscopic biopsy, endoscopic
operation and endoscopy. The size of the inflammatory part is important to determine a method of medical treatment.
However, it is not easy to measure absolute size of inflammatory part such as ulcer, cancer and polyp from the
endoscopic image. Therefore, it is required measuring the size of those part in endoscopy. In this paper, we propose a
new method to measure the absolute length in a straight line between arbitrary two points based on the photogrammetry
using endoscope with magnetic tracking sensor which gives camera position and angle. In this method, the stereo-corresponding
points between two endoscopic images are determined by the endoscopist without any apparatus of
projection and calculation to find the stereo correspondences, then the absolute length can be calculated on the basis of
the photogrammetry. The evaluation experiment using a checkerboard showed that the errors of the measurements are
less than 2% of the target length when the baseline is sufficiently-long.