Which type of marker is a survey monument?

A survey monument is specifically designed to serve as a permanent physical marker that indicates a geographical point. These monuments are used in surveying to accurately delineate property boundaries, establish control points, or signify important locations in mapping and land development. Made from durable materials, they are intended to withstand environmental elements and maintain their position over time, providing a reliable reference for surveyors.

The other options represent different types of markers or tools utilized in construction or planning contexts. Temporary construction markers, for example, are often used during the building phase to delineate work areas but are not intended to provide long-term geographical reference. Tools for grading land serve a specific function in shaping or leveling the terrain, rather than marking specific geographical points. Symbols in planning documents are used for visual representation in maps or plans but do not serve as physical markers in the field. Hence, the distinction of survey monuments as permanent, physical indicators of specific geographical locations is what makes this answer correct.