The remote sensor pointing straight down from the aircraft in a line perpendicular to Earth's surface is known as what?

The remote sensor pointing straight down from the aircraft in a line perpendicular to Earth's surface is known as what?

• A. Nadir
• B. Zenith
• C. Horizon
• D. Baseline

Answer: (A)

The direction straight down from the aircraft toward the ground is called the nadir. The ground point directly beneath the sensor is the nadir point, and imaging taken with the sensor oriented perpendicular to the surface is nadir viewing. Nadir imagery is favored in mapping because it minimizes distortions and keeps scale more uniform, making measurements and georeferencing easier. In contrast, the zenith is the point directly overhead, the horizon is the line where sky meets earth, and baseline is a reference distance used in measurements, not a directional term for the sensor.

The direction straight down from the aircraft toward the ground is called the nadir. The ground point directly beneath the sensor is the nadir point, and imaging taken with the sensor oriented perpendicular to the surface is nadir viewing. Nadir imagery is favored in mapping because it minimizes distortions and keeps scale more uniform, making measurements and georeferencing easier. In contrast, the zenith is the point directly overhead, the horizon is the line where sky meets earth, and baseline is a reference distance used in measurements, not a directional term for the sensor.