## Description

Calculates the height of a radar beam as a function of elevation and range, assuming the beam is emitted at surface level.

## Usage

 `1` ```beam_height(range, elev, k = 4/3, lat = 35, re = 6378, rp = 6357) ```

## Arguments

 `range` numeric. Slant range in m, the length of the skywave path between target and the radar antenna. `elev` numeric. Beam elevation in degrees. `k` Standard refraction coefficient. `lat` Geodetic latitude of the radar in degrees. `re` Earth equatorial radius in km. `rp` Earth polar radius in km.

## Details

To account for refraction of the beam towards the earth's surface, an effective earth's radius of k * (true radius) is assumed, with k = 4/3.

The earth's radius is approximated as a point on a spheroid surface, with `re` the longer equatorial radius, and `rp` the shorter polar radius. Typically uncertainties in refraction coefficient are relatively large, making oblateness of the earth and the dependence of earth radius with latitude only a small correction. Using default values assumes an average earth's radius of 6371 km.

## Value

numeric. Beam height in m.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11``` ```# beam height in meters at 10 km range for a 1 degree elevation beam: beam_height(10000, 1) # beam height in meters at 10 km range for a 3 and 5 degree elevation beam: beam_height(10000, c(3, 5)) # define ranges from 0 to 1000000 meter (100 km), in steps of 100 m: range <- seq(0, 100000, 100) # plot the beam height of the 0.5 degree elevation beam: plot(range, beam_height(range, 0.5), ylab = "beam height [m]", xlab = "range [m]") ```

bioRad documentation built on July 1, 2020, 10:18 p.m.