Nite Overlay - Overview

Generates an overlay to illustrate the day/night cycle. The night side is shaded slightly darker.

Works with D3.geo

The sun position is estimated using an adapted method from NOAA's solar calculator, which is based on equations from Astronomical Algorithms, by Jean Meeus.
More details: http://www.esrl.noaa.gov/gmd/grad/solcalc/calcdetails.html

Quick start

var width = 960;
var height = 480;

var projection = d3.geo.equirectangular()
    .scale(153)
    .translate([width / 2, height / 2])
    .precision(.1);

var path = d3.geo.path()
    .projection(projection);

var svg = d3.select('body').append('svg')
    .attr('width', width)
    .attr('height', height);
...
nite.init(svg);

Use refresh() method to update the overlay periodically. Perhaps via setInterval();

setInterval(function() { nite.refresh() }, 20 * 60 * 1000); // every 20m

Alternatively, a specific date can be selected via setDate() followed by a call to refresh() to redraw the overlay. Setting the date to null will cause nite overlay to use current date and time.

Note: *If the overlay is hidden and refresh() is called, the overlay position will not be updated.

Available methods

nite.setMap() set a specific map object -- Not Implemented Yet

nite.setDate(Date object) set a specific datetime, or null to use current datetime
nite.calculatePositionOfSun(Date object) returns LatLng for the specified date (has no effect on the overlay)
nite.refresh() Recalculate and refresh the position of the overlay
nite.isVisible() returns a boolean if the overlay is visible on the map
nite.show() Make the overlay visible
nite.hide() Hide the overlay
nite.getSunPosition() returns LatLng for the Sun
nite.getShadowPosition() returns LatLng for the night side