Bigous / polygon-utils

npm library with some polygon utils to be used both on node applications and web browsers.

Polygon geometry small library

The goal of this small library is to provide a set of useful and fast cartesian tools to work with polygons.

If you wanna go for hyperbolic coordinates like lat/long, you should use a conversion to a cartesian plane first, use this library and converts back to lat/long.

The useful utm-latlng library can be used to convert between lat/long and UTM coordinates (UTM is a cartesian plane representation of the earth).

The only gotcha is that you must use the same UTM zone for the calculus to work.

Using the lat/long coordinates directly is possible (like long been X and lat been Y), but you must keep in mind that all the measurements will be hyperbolic and some freaky things can happen.

Example:

The distance between two points in lat/long coordinates in meters is not

$\sqrt{\Delta x^2+\Delta y^2}$

it's $\approx$

$6371000 \times 2 \times atan2(\sqrt{ \sin^2{\frac{\Delta lat \times \frac{\pi}{180}}{2}} + \cos{lat_1 \times \frac{\pi}{180}}\times \cos{lat_2 \times \frac{\pi}{180}} \times \sin^2{\frac{\Delta lon \times \frac{\pi}{180}}{2}} } , \sqrt{1 - \sin^2{\frac{\Delta lat \times \frac{\pi}{180}}{2}} + \cos{lat_1 \times \frac{\pi}{180}}\times \cos{lat_2 \times \frac{\pi}{180}} \times \sin^2{\frac{\Delta lon \times \frac{\pi}{180}}{2}}})$

So... Have fun ;)

PS: If you need a more sofisticated and complete library, I'd recommend using flatten-js. It's really nice and well documented. I've done this because I wanted it to be simple and fast for my pourposes (and for fun :) ). You can compare the ray_soot from flatten and mine to understand what I mean.

License MIT

@author Richard Natal - Bigous