Documentation

grazingang

Grazing angle of surface target

Syntax

grazAng = grazingang(H,R)
grazAng = grazingang(H,R,MODEL)
grazAng = grazingang(H,R,MODEL,Re)

Description

grazAng = grazingang(H,R) returns the grazing angle for a sensor H meters above the surface, to surface targets R meters away. The computation assumes a curved earth model with an effective earth radius of approximately 4/3 times the actual earth radius.

grazAng = grazingang(H,R,MODEL) specifies the earth model used to compute the grazing angle. MODEL is either 'Flat' or 'Curved'.

grazAng = grazingang(H,R,MODEL,Re) specifies the effective earth radius. Effective earth radius applies to a curved earth model. When MODEL is 'Flat', the function ignores Re.

Input Arguments

 H Height of the sensor above the surface, in meters. This argument can be a scalar or a vector. If both H and R are nonscalar, they must have the same dimensions. R Distance in meters from the sensor to the surface target. This argument can be a scalar or a vector. If both H and R are nonscalar, they must have the same dimensions. R must be between H and the horizon range determined by H. MODEL Earth model, as one of | 'Curved' | 'Flat' |. Default: 'Curved' Re Effective earth radius in meters. This argument requires a positive scalar value. Default: effearthradius, which is approximately 4/3 times the actual earth radius

Output Arguments

 grazAng Grazing angle, in degrees. The size of grazAng is the larger of size(H) and size(R).

Examples

collapse all

Determine the grazing angle (in degrees) of a path to a ground target located 1.0 km from a sensor. The sensor is mounted on a platform that is 300 m above the ground.

grazAng = grazingang(300,1.0e3)
grazAng = 17.4544

collapse all

Grazing Angle

The grazing angle is the angle between a line from the sensor to a surface target, and a tangent to the earth at the site of that target. For the curved earth model with an effective earth radius of Re, the grazing angle is:

${\mathrm{sin}}^{-1}\left(\frac{{H}^{2}+2H{R}_{e}-{R}^{2}}{2R{R}_{e}}\right)$

For the flat earth model, the grazing angle is:

${\mathrm{sin}}^{-1}\left(\frac{H}{R}\right)$

References

 Long, Maurice W. Radar Reflectivity of Land and Sea, 3rd Ed. Boston: Artech House, 2001.

 Ward, J. “Space-Time Adaptive Processing for Airborne Radar Data Systems,” Technical Report 1015, MIT Lincoln Laboratory, December, 1994.