CLASS SYSTEMATIC RANDOM 
Atmosphere Path length Inhomogeneities 
Geometry Clouds 
Sun Position Time, Date 
Location 
Scan Geometry Nadir angle Angle errors 
Azimuth w.r.t. sun Terrain profile 
Altitude 
Aperture effects System noise 
Gain changes 
FIGURE 2. SOURCES OF VARIATIONS IN MULTISPECTRAL SCANNER SIG- 
NALS (72IRO-1-58)