shotGroups (version 0.7.1)

getDistance: Get distance based on absolute and angular size

Description

Calculates the distance to an object based on the object's absolute and angular size.

Usage

getDistance(x, angular, conversion = 'm2cm', type = c('deg', 'rad', 'MOA', 'SMOA', 'mrad', 'mil'))

Arguments

x

a numerical vector of absolute object sizes.

angular

a numerical vector of angular object sizes.

conversion

how to convert the measurement unit for the returned distance to object to that of given absolute object size. Either a character vector indicating the conversion like 'm2cm' for meter to centimeter, 'yd2in' for yards to inches, or 'ft2cm' for feet to cm. Imperial (yd, ft, in) and metric units (m, cm, mm) can be freely mixed. Alternatively, a numerical vector giving the multiplication factor for conversion: 100 for m to cm, 36 for yd to in, and 12 for ft to in.

type

type of angular measure used in angular: 'deg' for degree, 'rad' for radian, 'MOA' for minute of angle, 'SMOA' for Shooter's MOA, 'mrad' for milliradian, 'mil' for NATO mil. See details.

Value

Details

1 MOA (minute of angle, arcmin) = 1/60 degree. Shooter's MOA = SMOA = Inches Per Hundred Yards IPHY. 1 inch at 100 yards = 1 SMOA. 1 milliradian = 1/1000 radian. 1 mil = 2*pi/6400 radian (NATO definition: the circle circumference is divided into 6400 mils). Details are given in the vignette, see vignette('shotGroups')

See Also

getMOA, fromMOA

Examples

size <- seq(1, 20, by=5)   # inch
dst  <- 100                # yard

# get angular size in MOA from absolute size
angular <- getMOA(size, dst=dst, conversion='yd2in', type='MOA')

# this should return dst throughout
getDistance(size, angular=angular, conversion='yd2in', type='MOA')