A Modified Direct-reading Azimuth Protractor.
J Geol Educ 1977 Jan; 25(1):13-15
A procedure is described for constructing a direct-reading azimuth protractor (drap) that is a variant of the drap described in Bureau of Mines Information Circular 8617 by D. D. Bolstad and M. A. Mahtab. The original drap has been shown to be an effective instrument for mapping fracture and joint-surface orientation in underground mines where magnetic disturbances affect a typical geologic pocket transit. In addition, there is an azimuth-type compass available that, with the protractor modification and addition of an azimuth arm, can be adapted for use as a drap. The modification of the protractor does not affect the mechanical operation of the compass in any way, and the azimuth arm can be removed within seconds, and the compass used normally, to determine the dip azimuths and dip angles of joints in the field or in areas not affected by magnetic disturbances. The modified drap requires less machining and assembly work than the original drap.
J. Geol. Educ., V. 25, No. 1, January 1977, PP. 13-15