Surveying Control Points
Definition
Surveying control points are precisely measured locations used to anchor mapping and engineering projects to a common coordinate reference system. They include horizontal control (latitude/longitude or easting/northing) and vertical control (ellipsoid height or orthometric elevation), often with GNSS benchmarks and marks in stable monuments. Control networks propagate accuracy from primary to secondary points through rigorous adjustments. Metadata record monument condition, measurement methods, epochs, and expected accuracy.
Application
Engineers reference control for construction staking; mapping teams align aerial surveys; utilities register asset maps; and scientists monitor land motion over time. Reliable control prevents cumulative misalignments across projects and contractors.
FAQ
Why do epochs matter for GNSS-based control?
Tectonic motion and subsidence move coordinates over time; specifying the epoch ensures users transform positions correctly to current frames.
How should control be checked before use on a project?
Occupy a sample of marks with GNSS, compare to published coordinates, and inspect monuments for disturbance; update descriptions if access or surroundings changed.
When is it necessary to establish temporary control?
If permanent marks are distant or obstructed, set site-specific control tied to the national network; remove or document it after the project.
What are good practices for sharing control with partners?
Provide coordinate values with CRS and epoch, photos, access notes, and uncertainty; include contact info for reporting damage or changes.
SUPPORT
© 2025 GISCARTA