Geometrical instruments – Miscellaneous – Light direction
Patent
1990-01-22
1991-04-16
Will, Thomas B.
Geometrical instruments
Miscellaneous
Light direction
33465, 33431, 33471, B43L 710
Patent
active
050071742
ABSTRACT:
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.
REFERENCES:
patent: 932907 (1909-08-01), Rydman
patent: 977048 (1910-11-01), Smith
patent: 1299978 (1919-04-01), MacDowney
patent: 2238190 (1941-04-01), Sawtelle
patent: 2641843 (1953-06-01), Hart et al.
patent: 3248793 (1966-05-01), Anderson
patent: 3280464 (1966-10-01), Warner
patent: 3303568 (1967-02-01), Geiger
patent: 3813783 (1974-06-01), Price
patent: 3855706 (1974-12-01), Price
patent: 4383372 (1983-05-01), Zane et al.
Aerial Photo Scale Protractor.
Drawing and Drafting Catalog, p. 147 and enlargement.
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