aitoff: Convert longitude, latitude to X,Y using an AITOFF projection

In astrolibR: Astronomy Users Library

Description

Convert longitude, latitude to X,Y using an AITOFF projection

Usage

aitoff(l,b)

Arguments

l	longitude, scalar or vector, in degrees
b	latitude, scalar or vector (same length as l), in degrees

Details

This procedure can be used to create an all-sky map in Galactic coordinates with an equal-area Aitoff projection. Output map coordinates are zero longitude centered. See AIPS memo No. 46, page 4, for details of the algorithm. This version of AITOFF assumes the projection is centered at b=0 degrees.

Several polar equal-area map projections are provided by the CRAN package mapproj.

Value

x	x coordinate in range -180 to +180, same length as l.
yx	y coordinate in range -90 to +90, same length as l.

Author(s)

Written W.B. Landsman STX December 1989

R adaptation by Arnab Chakraborty June 2013

References

Additional Non-linear Coordinates in AIPS, Eric W. Greisen, AIPS Memo 46, 1993 ftp://ftp.aoc.nrao.edu/pub/software/aips/TEXT/PUBL/AIPSMEMO46.PS.

Examples

aitoff(227.23,-8.890)  #  celestial location of Sirius in Galactic coordinates

Example output

$x
[1] -137.922

$y
[1] -11.77253

astrolibR documentation built on May 2, 2019, 3:26 a.m.