| 摘要 |
PCT No. PCT/SE81/00018 Sec. 371 Date Sep. 29, 1981 Sec. 102(e) Date Sep. 29, 1981 PCT Filed Jan. 23, 1981 PCT Pub. No. WO81/02200 PCT Pub. Date Aug. 6, 1981.An instrument for use when levelling and when laying-out right angles comprises upright mirrors (1) which intersect each other at right angles and are carried on a frame structure (2) that is adjustable relative to the horizontal plane, said mirrors having markings (4) located on the same level relative to a plane (12) which forms right angles with all mirror surfaces, thereby to enable a leveling operation or a laying-out to be carried out by a single person. |
