How can I properly place checkpoints and ground control points?

Question

How can I properly place checkpoints and ground control points?

Answer/Cause

Recommended Locations for Check Point and Ground Control Point Placement

Flat, Level Areas

Reason: Ensures consistent elevation around the control point, leading to accurate measurements.

Areas with No Irregularities Around the Control Point

Reason: This helps to reduce the variability in the 3D data generated by SfM, stabilizing the nearby points and leading to more accurate comparisons with measured values. As a result, more reliable validation is possible. Before placement, please ensure the ground around the checkpoints is leveled.

Solid Ground

Reason: Provides stability for the survey pole, allowing for precise measurements.

Non-Recommended Locations for Check Point and Ground Control Point Placement

Areas with Slopes or Uneven Surfaces

Reason: Slopes cause inconsistencies in elevation around the control point, making accurate surveying difficult.

Soft Ground

Reason: In muddy or soft ground, such as after rain or on volcanic ash, the survey pole may sink, causing discrepancies between the ground surface and the control point.

Areas with Overgrown Vegetation

Reason: In drone photogrammetry, point clouds are generated based on visible surfaces in the photos. Overgrown areas may cause a difference of several centimeters between the ground and the vegetation surface. It is preferable to place checkpoints on visible, bare soil.

Areas with Overhead Obstacles (e.g., Trees)

Reason: Overhead obstacles like tree branches can obstruct drone photography and satellite signal reception, leading to reduced accuracy. Checkpoints should be placed in areas free from overhead obstructions whenever possible.