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grazingang

Grazing angle of surface target

Syntax

grazAng = grazingang(H,R)
grazAng = grazingang(H,R,MODEL)
grazAng = grazingang(H,R,MODEL,Re)
grazAng = grazAng = grazingang(___,'TargetHeight',TGTHT)

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) also specifies the earth model used to compute the grazing angle. MODEL is either 'Flat' or 'Curved'.

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

grazAng = grazAng = grazingang(___,'TargetHeight',TGTHT) also specifies the target height, TGTHT above the surface as either a scalar or a vector. If any combination of ht, R, and TGTHT are vectors, then the dimensions must be equal. R must be greater than or equal to the absolute value of the difference of HT and TGTHT.

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 TGTHT.

MODEL

Earth model, as one of | 'Curved' | 'Flat' |.

Default: 'Curved'

Re

Effective earth radius in meters. This argument must be a positive scalar value. You can used effearthradius to compute the effective radius.

Default: effearthradius, which is approximately 4/3 times the actual earth radius

TGTHT

Target height above surface, specified as a scalar or vector. If any combination of H, R, and TGTHT are vectors, then their sizes must be equal. R must be greater than or equal to the absolute value of the difference of H and TGTHT. A surface target has a TGTHT of zero.

Default: 0

Output Arguments

grazAng

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

Examples

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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

More About

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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:

sin1(H2+2HReR22RRe)

For the flat earth model, the grazing angle is:

sin1(HR)

References

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

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

Extended Capabilities

Introduced in R2021a