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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)

## 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

Determine the grazing angle of a ground target located 1000 m away from the sensor. The sensor is mounted on a platform that is 300 m above the ground.

`grazAng = grazingang(300,1000);`

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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:

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

For the flat earth model, the grazing angle is:

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

## References

[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.