Surveyor's prism target

An improved prism target for use with a surveyor's total station instrument whereby the surveyor can use the prism target for obtaining distance measurements by reflecting an energy beam and as an accurate visual target to actually set and locate the surveyor's points, said prism target comprising;

• (a) corner cube prism having a face surface, an outer surface, and three equal area flat reflective surfaces formed at a rear end opposite to the front face surface, said reflective surfaces being arranged 90.degree. to each other and forming a plurality of ridge lines where each of the surfaces intersect with an adjacent surface and all three surfaces meet at a center apex, each of said ridge lines extending from the outer surface to the apex,
• (b) a thin stripe is formed on at least two of said ridge lines to form a radial center target when the prism is viewed through the front face surface,
• (c) the corner cube prism is mounted within a case to protect the prism from damage and contamination, said case includes a mounting means for attaching the case and said prism to a suitable prism support means having a vertical center line axis,
• (d) said mounting means includes means for tiltably rotating the case and prism around a horizontal axis, and
• (e) the radial center target appears on a hypothetical plane which is offset forward of the apex of the prism a predetermined offset distance and said horizontal tilt axis passes through said hypothetical plane.

A method of making a prism target which includes a combination visual target and a retro-reflective device so that a surveyor can set and locate a number of points from one set-up location;

• said method including the steps of:
• a) forming a glass prism having a cylindrical outer surface, a flat face surface formed at one end and a plurality of flat reflective surfaces formed at an opposite rear end;
• b) each of two intersecting reflective surfaces forming a ridge line therebetween and all of said ridge lines intersect at a center apex at the rear end of said prism;
• and
• c) coating the edge of at least two of the ridge lines with a highly visible material to form thin stripes along said ridge lines so that a visual radial center target appears within the prism when viewed through the flat face surface.

An improved prism target for use with a surveyor's total station instrument whereby the surveyor can use the prism target for obtaining distance measurements by reflecting an energy beam and providing an accurate visual target to actually set and locate surveyor's points, said prism target comprising:

• a) a corner cube cylindrical prism having a face surface, an outer cylindrical surface, and three equal area flat reflective surfaces formed at a rear end opposite to the front face surface, said reflective surfaces being arranged 90 degrees to each other and forming a plurality of ridge lines where each of the surfaces intersect with an adjacent surface and all three surfaces meet at a center apex, each of said ridge lines extending from the outer cylindrical surface to the apex;
• b) a thin stripe is formed on at least two of said ridge lines to form a radial center target when the prism is viewed through the front face surface;
• c) the thin stripes extend from the outer surface to the apex and are formed from highly visible material;
• and
• d) the prism is mounted within a case having a base means for attaching the case and the prism to a suitable prism support means having a vertical centerline axis and said prism is positioned within said case so that the apex of the prism is aligned with the axis of said support means.

An exterior sighting target for use with a surveyor's retro-reflective prism target, said surveyor's prism target having a front face surface and a plurality of reflective surfaces meeting at a center apex at a rear portion of the prism, the reflective surfaces having a unique coating pattern which produces an internal visual center target which appears to lie on a hypothetical plane parallel to the front face surface and forward of the apex a specific offset distance, said prism being suitably mounted within a case for attachment to a support means, said exterior sighting target surprising:

• a) an enlarged thin planar member having a front surface and an opposite rear surface and an outer perimeter edge;
• b) first mounting means centrally positioned within said thin planar member for retaining and securing the prism and case so that the front face of the prism is parallel with the front surface of the planar member which is arranged to coincide with the hypothetical offset visual target plane of the prism;
• c) means attached to said planar member and having a second mounting means for connecting the planar member to a suitable support means having a vertical centerline axis, said attached means being arranged to position the apex of the prism in alignment with the centerline axis of the support means;
• and
• d) indicia provided on the front surface of the planar member, said indicia having an appearance which contrasts with the front surface of the exterior target, said indicia having a design which visually aligns with the center of the visual target of the prism.