Waikiki residents report strange green light in the sky

Residents in the Waikiki area may have seen an airplane in the sky, shining a green light over the city.

Over the past two nights, residents reported seeing the plane after midnight.

One person posted a home video on YouTube.

But the Federal Aviation Administration says it’s all part of aerial survey work being conducted by the Army Corps of Engineers.

They say the work was completed early Monday morning.

Lidar 101: An Introduction to Lidar Technology, Data, and Applications (PDF)

What Is Lidar?
Lidar, which is commonly spelled LiDAR and also known as LADAR or laser altimetry, is an acronym for light detection and ranging. It refers to a remote sensing technology that emits intense, focused beams of light and measures the time it takes for the reflections to be detected by the sensor. This information is used to compute ranges, or distances, to objects. In this manner, lidar is analogous to radar (radio detecting and ranging), except that it is based on discrete pulses of laser light. The three-dimensional coordinates (e.g., x,y,z or latitude, longitude, and elevation) of the target objects are computed from 1) the time difference between the laser pulse being emitted and returned, 2) the angle at which the pulse was “fired,” and 3) the absolute location of the sensor on or above the surface of the Earth.

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