What type of line is characterized by heavy broken lines made of one long and two short dashes alternately spaced with arrow heads at both ends?

The type of line characterized by heavy broken lines made of one long dash and two short dashes, alternately spaced with arrowheads at both ends, is known as a viewing plane line. This line style indicates the limits or extent of a viewing plane—essentially the area from which an observer can see an object or point of interest on a plan or drawing.

Viewing plane lines help convey the perspective or sightlines in design and engineering drawings, making them crucial for understanding spatial relationships and visual aspects in plans. These lines underscore important viewpoints or strategic locations where critical sightlines are necessary for the understanding of the project’s design.

In contrast, boundary lines typically delineate property lines or limits of a site, often shown in solid or dashed styles without the specific alternation that characterizes viewing plane lines. Reference lines are used for alignment purposes and measurements, while offset lines indicate a parallel line at a set distance from a reference line. Each of these has distinct visual representations that serve specific functions in surveying and earthwork drawings.