The profile serves as a control from which line of sight transits to other points results in a collection of located spots that allow contouring. The principles underlying this are summarized on this page. To consider altimetry, we must go from point surveying to linear surveying of the Earth's surface. We can readily plot these elevations as profiles. A series of parallel profiles serve as a framework for contouring.
Laser is an acronym for l ight a mplification by s timulated e mission of r adiation.
Much of the light passes sidewards out of the crystal, but light moving along the axial zone of the cylinder encounters other Cr ions as it reflects repeatedly. Other laser materials include gallium arsenide and excited gases such as neon or helium. Both visible and infra-red wavelength light can be generated in this way. Laser altimetry has been conducted from aircraft platforms for several decades. Aircraft can be scheduled to fly in good weather, offsetting the main disadvantage of using lasers coming from cloud interference with the light beam.