Page 46 - Digital Analysis of Remotely Sensed Imagery

Overview 19

Band 6
Wavelength Band 4
Band 5
Band 3
Band 2
Band 1

FIGURE 1.10 The multispectral concept in obtaining remotely sensed data.
It is a common practice to obtain multispectral data in spaceborne remote
sensing in which the low spatial resolution is compensated for by a fi ner
spectral resolution.

8-bit quantization level has evolved into a level as high as 11 bits,
thanks to advances in sensing technology. With the use of more bits in
recording remotely sensed data, the radiative energy received at the
sensor is sliced into more levels radiometrically (Fig. 1.11), which

Level of sampling the signal

Intensity

Time

FIGURE 1.11 Quantization of energy refl ected from a ground target is
converted into an electrical signal whose intensity is proportional to its
refl ectance. The interval of sampling the signal intensity determines the
radiometric resolution of the satellite imagery, or its ability to discriminate
subtle variation in refl ectance.