Coregistration of multispectral imagery for spaceborne detection of incipient forest fires

摘要

Discrimination of small wildfires by dual-wavelength imaging at high spatial resolution (10 m) must be made against a variable background (scene clutter) caused by diffuse and specular sunlight reflections and self-emission from the scene. Small fires can be readily detected at wavelengths longer than about 1400 nm in the near infrared. From a specific ground spot, the ratio of signal intensities in bands near 2400 and 3700 nm gives an 'effective temperature' that is a useful discriminant against scene clutter. Co- registration of the scene images in the two wavelength regions is important when applying the technique, particularly from a space platform where the angular size of the ground footprint is small. This paper shows that atmospheric refraction and turbulence can be ignored, while window wedge angles, lens centration errors and spectral variations in the size of the ground footprint must be dealt with by calibration or additional signal processing.