What is the required detail of contour intervals in surveys?

Contour intervals in surveys are essential for accurately representing the terrain's elevation features. The requirement that they meet national mapping accuracy standards means that the intervals must be appropriately detailed to ensure that the resulting maps are both reliable and precise. This adherence to standards is critical for various applications, such as topographic mapping, hydrology, and land use planning, where accurate representation of terrain affects decision-making.

National mapping accuracy standards ensure that there is consistency and reliability in the data presented, which is crucial for users relying on these surveys for engineering, construction, environmental assessments, and other professional fields. By specifying the contour intervals to align with these standards, surveyors create a framework where users of the map can have confidence in the represented elevation changes and how they influence the surrounding landscape.

The other options do not reflect the importance of accuracy in contour intervals; they imply variability or lack of necessity that contradicts established professional practices in surveying.