getMOA {shotGroups}

Conversion of absolute size to angular diameter

Description

Converts object size to angular diameter (degree, radian, minute of angle MOA = arcminute, Shooter's MOA SMOA, milliradian mrad, NATO mil).

Usage

getMOA(x, dst, conversion,
       type = c('deg', 'rad', 'MOA', 'SMOA', 'mrad', 'mil'))

Arguments

x

a numerical vector of object sizes.

dst

a numerical vector of viewing distances.

conversion

how to convert the measurement unit for distance to target to that of the (x,y)-coordinates. Either a character vector indicating the conversion such as '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 diameter: '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.

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') .

If package shiny is installed, an interactive web app for this functionality can be run with runGUI("angular").

Value

A numerical vector with the angular diameter values.

See Also

fromMOA, getDistance

Examples

size <- seq(1, 20, by=5)   # inch
dst  <- 100                # yard
getMOA(size, dst=dst, conversion='yd2in', type='MOA')

# this should return objSize
MOA <- getMOA(size, dst=dst, conversion='yd2in', type='MOA')
fromMOA(MOA, dst=dst, conversion='yd2in', type='MOA')

# SMOA
getMOA(c(1, 2, 5), dst=100, conversion='yd2in', type='SMOA')

# milliradian
getMOA(c(10, 20, 50), dst=100, conversion='m2mm', type='mrad')