Under what condition is the positive height of a point in underground surveying noted?

In underground surveying, a positive height of a point is noted when the sighted point is above the station. This context relates to how vertical distances are measured in relation to a reference point or benchmark, which in this case is the station itself.

When surveying underground, it is essential to establish a clear reference for interpreting levels and elevations. A point that is physically located above the station implies that its height can be measured in a positive manner since it exceeds the elevation of the reference point. This is a standard approach to measurements in surveying, as it allows surveyors to understand vertical relationships effectively.

Conversely, if the point is below the station, at the same level, or not clearly visible from the surface, these situations would not yield a positive height. For example, points at the same level would typically register as zero height, while points beneath the station would result in negative height values. The visibility of the point to the surface is also irrelevant in this context, as it does not directly affect the height measurement.