Nite Overlay - Overview

Generates an overlay to illustrate the day/night cycle. There are 4 shade levels going from light to dark. They are civil twilight, nautical twilight, astronomical twilight and night.

Works with Google Maps API v3

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: https://gml.noaa.gov/grad/solcalc/calcdetails.html

Might not work on some mobile devices. I've not explored the reason for this

Quick start

var map = google.maps.Map(...);
nite.init(map);

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

setInterval(function() { nite.refresh() }, 10000); // every 10s

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.
Not until the overlay is visible again.

Available methods

nite.setMap() set a specific map object
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