Survey stations placed on the ground which are visible on aerial photographs – the coordinates of this ground control are used to orient and scale the air photographs so that maps can be plotted from them.
Survey stations placed on the ground which are visible on aerial photographs – the coordinates of this ground control are used to orient and scale the air photographs so that maps can be plotted from them.
Existing survey stations that can be used as the starting point for new surveys. See also Horizontal Control and Vertical Control.