BENCHMARKS

Figure3-13.—Telescoping tram bar and related equipment. BENCHMARKS Benchmarks are small metal plates that contain an engraved cross. The plates are either brazed or welded to some rigid portion of the ship’s structure at a posi- tion where the engraved cross can be sighted on with the reference element (director). A benchmark maybe engraved on a flat plate for bulkhead mounting or on a block with an inclined surface so that the mark is clearly visible on the ship’s deck. Benchmarks are reference marks used in alignment to establish the angular relationships (elevation and train) of an ele- ment’s line of sight to the ship’s structure. When an element is sighted at its benchmark, its dial readings should agree with recorded values. If there is dis- agreement, alignment of the element is necessary. Figure 3-14 shows two typical benchmarks. 3-11