hea

healpix

convert between lonlat and HEALPix coordinates

Showing:

Popularity

Downloads/wk

0

GitHub Stars

16

Maintenance

Last Commit

5yrs ago

Contributors

1

Package

Dependencies

0

License

BSD-2-Clause

Type Definitions

Tree-Shakeable

No?

Categories

Readme

healpix

convert between lonlat and HEALPix coordinates

HEALPix coordinates are an equal area projection very similar to cube mapping. This coordinate system is used heavily in cosmology, where equal-area and uniform point distribution are important for density comparisons and binning.

The HEALPix algorithm is described in the paper Mapping on the HEALPix grid

example

lon/lat to x/y

var healpix = require('healpix')(4,3)
var phi = Number(process.argv[2]) / 180 * Math.PI
var theta = Number(process.argv[3]) / 180 * Math.PI
var out = healpix.ang2xy([], phi, theta)
console.log(out.join(' '))

output:

$ node lonlat2xy.js -148 65
-2.476485479234211 -1.1544044416499766

x/y to lon/lat

var healpix = require('healpix')(4,3)
var PI = Math.PI
var x = Number(process.argv[2])
var y = Number(process.argv[3])
var out = healpix.xy2ang([], x, y)
console.log(out[0]*180/PI, out[1]*180/PI)
$ node xy2lonlat.js -2.476485479234211 -1.1544044416499766
-148.00000000000003 -65

api

var healpix = require('healpix')

var hp = healpix(H, K)

Create a healpix projection parameterized by H,K.

hp.ang2xy(out, phi, theta)

Calculate [x,y] on the healpix projection given:

  • phi - longitude in radians
  • theta - latitude in radians

Set [x,y] and return out.

hp.xy2ang(out, x, y)

Calculate [phi,theta] from [x,y] on the healpix projection.

Set [phi,theta] and return out.

install

npm install healpix

license

BSD

Rate & Review

Great Documentation0
Easy to Use0
Performant0
Highly Customizable0
Bleeding Edge0
Responsive Maintainers0
Poor Documentation0
Hard to Use0
Slow0
Buggy0
Abandoned0
Unwelcoming Community0
100
No reviews found
Be the first to rate

Alternatives

No alternatives found

Tutorials

No tutorials found
Add a tutorial