| 摘要 |
A measuring device for topographic sheets includes top and bottom transparent arms that pivot relative to a connecting pivot. A plurality of different distance scales on each arm provide for measuring the distance between two points on a topographic sheet. A protractor on the top arm and pointer marks on the bottom arm provide an indication of the extent of rotation of one arm relative to the other. The device is suitable for measuring distance between points, azimuth, scale and position of true north on an aerial photo. A slidable cross-hair member is used on either arm. One embodiment has a protractor affixed to the top arm and another has the protractor rotatable and removable from the top arm. A third embodiment has the bottom arm offset from the center of the protractor and the bottom arm slidable relative to the top arm.
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