# surfacegamma

Gamma value for different terrains

Since R2021a

## Syntax

``G = surfacegamma(TerrainType)``
``G = surfacegamma(TerrainType,FREQ)``
``surfacegamma``

## Description

````G = surfacegamma(TerrainType)` returns the γ value for the specified terrain. The γ value is for an operating frequency of 10 GHz.```

example

````G = surfacegamma(TerrainType,FREQ)` specifies the operating frequency of the system.```
````surfacegamma` displays several terrain types and their corresponding γ values. These γ values are for an operating frequency of 10 GHz.```

## Examples

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Determine the γ value for a wooded area, and then simulate the clutter return from that area. Assume the radar system uses a single cosine pattern antenna element and has an operating frequency of 300 MHz.

```fc = 300e6; g = surfacegamma('woods',fc); clutter = constantGammaClutter('Gamma',g, ... 'Sensor',phased.CosineAntennaElement, ... 'OperatingFrequency',fc); x = clutter(); r = (0:numel(x)-1)/(2*clutter.SampleRate) * ... clutter.PropagationSpeed; plot(r,abs(x)) xlabel('Range (m)') ylabel('Clutter Magnitude (V)') title('Clutter Return vs. Range')```

## Input Arguments

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Terrain type, specified as one of these:

• `"Sea State 3"`

• `"Sea State 5"`

• `"Woods"`

• `"Metropolitan"`

• `"Rugged Mountain"`

• `"Farmland"`

• `"Wooded Hill"`

• `"Flatland"`

Data Types: `char` | `string`

Operating frequency of radar system in hertz, specified as a scalar or a vector.

Data Types: `double`

## Output Arguments

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Gamma value, γ, in decibels, for constant-γ clutter model, returned as a scalar.

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### Gamma

A frequently used model for clutter simulation is the constant gamma model. This model uses a parameter, γ, to describe clutter characteristics of different types of terrain. Values of γ are derived from measurements.

## Algorithms

The γ values for the terrain types `"Sea State 3"`, `"Sea State 5"`, `"Woods"`, `"Metropolitan"`, and `"Rugged Mountain"` are from [2]. The γ values for the terrain types `"Farmland"`, `"Wooded Hill"`, and `"Flatland"` are from [3].

Measurements provide values of γ for a system operating at 10 GHz. The γ value for a system operating at frequency f is:

`$\gamma ={\gamma }_{0}+5\mathrm{log}\left(\frac{f}{{f}_{0}}\right)$`

where γ0 is the value at frequency f0 = 10 GHz.

## References

[1] Barton, David. "Land Clutter Models for Radar Design and Analysis," Proceedings of the IEEE. Vol. 73, Number 2, February, 1985, pp. 198–204.

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

[3] Nathanson, Fred E., J. Patrick Reilly, and Marvin N. Cohen. Radar Design Principles, 2nd Ed. Mendham, NJ: SciTech Publishing, 1999.

## Version History

Introduced in R2021a