| 摘要 |
In order to plot on a map the position of an observer with respect to 3 significant points (landmarks), according to which the observer uses a device for angular sighting and construction making it possible, using a set of mirrors, to separate rules, pivoting at the same point, by the exact value of the angles formed between the 3 points sited in pairs, these angles to fix in space, and to plot these solid angles directly onto the map, in order to find thereon his/her position at their vertex. This instrument consists of 3 rules 1, 2 and 3 rotating about the hollow pivot 4. The images found in the direction of 3 are reflected towards the eye of the observer by a vertical mirror 8 with a double reflecting face, fixed onto the wheel 7, which rotates through an angle equal to half the angle in question, by virtue of the movement of the toothed wheels 5, 6 and 7, so that the observer can superpose the directly viewed image lined up along 1 with the other reflected image lined up along 3. The rule 2 acts as a reference for the first sighting. The 2 angles are locked and plotted directly onto the map, in order to determine thereon the position situated under the spindle 4. A more precise version with 2 mirrors is provided as a variant. The instrument according to the invention is more particularly intended for navigation and topography (surveying). <IMAGE>
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