geo-math

~ < 10^2 lines.

Goal: Provide a minimal set of commonly needed geolocation functions using the small angle approximation; two main methods, and a handful of trivial (but useful) utility methods.

What About Large Distances?: Distances on the order of city or state level will not need exact formulas to get accurate results. We gain performance by sacrificing unnecessary precision.

Underneath: Cache commonly used values, make assumptions about input to speed up calculations, make the small angle approximation whenever possible, include corrections for nontrivial longitudinal squeezing, which is dependent on latitude.

Tip: Please only use this if you do not deal with large distance scales.

Full API

Global Object: GeoMath

Main methods: distance, randomCoords

Meta methods: setUnits, getUnits

Basic utility methods: randomReal, toRadians, toDegrees, toCanonicalCoords, toMongoCoords, toMiles, toKm

//canonical coords
var cc = {
	lat: Number,
	lng: Number
}

//mongo coords
var mc = {
	type: "Point",
	coordinates: [Number,Number]
}

Main Methods:

Distance between two points.

//only takes two canonical coordinates.
//dist is returned in either km or miles, dep. on GeoMath.setUnits.

var dist = GeoMath.distance(cc1, cc2)

Random coordinates on earth.

var pointOnEarth = GeoMath.randomCoords();

Random coordinates in a circle around your location.

//you can get a random coordinate pair around another one.

var max_dist = 10 

var cc_random = GeoMath.randomCoords(cc_center, max_dist);

Random coordinates in an annulus around your location.

//can ask for a random coord around a center point, at least a certain min_dist away.

var min_dist = 2
var max_dist = 5

var cc_random = GeoMath.randomCoords(cc_center, max_dist, min_dist)

Utility methods:

Setting units, default is SI.

//set units to SI, input/output in mi.

GeoMath.setUnits("SI")

//set units to US, input/output in mi.

GeoMath.setUnits("US")

Converting lat/lng or MongoDB coords to canonincal form.

//define canonical form as: {lat: Number, lng: Number}
//both snippets return canonical coordinates.

GeoMath.toCanonicalCoords(48.664, -76.234)
var mongoDBloc= {
  type: "Point",
  coordinates: [-76.234, 48.664]
}

GeoMath.toCanonicalCoords(mongoDBloc)

Using GeoMath.toMongoCoords is similar.

Self Explanatory methods.

You can use GeoMath.randomReal(min,max) to get a random real number between min and max. You can use GeoMath.getUnits() to return the current units GeoMath is using. Functions are provided to convert between degrees and radians and between km and miles.

Streemo/geo-math