Page 63 - Digital Analysis of Remotely Sensed Imagery

36 Cha pte r T w o

Image Properties Multispectral Panchromatic
Wavelength (μm) 0.50–0.59 0.51–0.73
0.61–0.68
0.79–0.89
∗
SWIR (shortwave infrared) 1.58–1.75
†
Spatial resolution at nadir (m) 20 10 (2.5 or 5)
Swath width at nadir (km) 60 60
Number of pixels per line 3,000 6,000
Quantization level (bits) 8 6

∗ Available in SPOT 4 and SPOT 5 only.
†
Figure in the bracket applies to SPOT 5 only.
TABLE 2.10 Characteristics of SPOT Satellite Data

Detector array Focal plane

Lens

Scanning
direction

Ground sampling size
Swath width
Satellite motion

FIGURE 2.3 The “pushbroom” concept of ground scanning adopted by SPOT
satellites. In this mode the scanning direction is in agreement with the
satellite motion direction, hence shortening scanning duration to achieve
a higher geometric fi delity at the expense of using more detectors.