This is just a tiny library which abstracts away working with GPS points and bounds on the Mercator map.
Ruby Shell
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Failed to load latest commit information.
bin
examples
lib
spec
.gitignore
.rspec
.travis.yml
.yardopts
Gemfile
LICENSE.txt
README.md
Rakefile
geo.gemspec

README.md

Geo Build Status Code Climate

This is just a tiny library (actually a gem but not published on rubygems.org) which abstracts away working with GPS points and bounds on the Mercator map.

It was created because I wanted to give Mapbox a set of GPS (lat/lon) points and it would return a properly centered and zoomed in static map. Except that it doesn't do that.

So I crawled around the web and composed all I needed from those three libraries:

None of them do all I needed and some of them are really cryptic. It seems to work properly but if you find a bug, please let me know.

What does it do?

The Geo::Viewport class initializer expects map bounds array (WSEN: westmost, southmost, eastmost and northmost coordinates) and an array of mercator map dimensions in pixels. It than calculates the center, the zoom level and a new set of bounds for given dimensions. Why new bounds? Because zoom level is a whole number so the map bounds are expanded a bit to reflect that. The instance methods are used to get those properties.

The Geo::Utils module is a place for all kinds of conversion methods but there is one externally useful: the bounds method. It expects an array of GPS points and returns a [w, s, e, n] map bounds array which then can be fed into the initializer.

Usage

See examples, too.

# Photos longitude and latitude.
gps_data = [
  [6.9558,             50.941691666666664],
  [6.956291666666667,  50.94157777777777],
  [6.9201500000000005, 50.948233333333334],
  [9.188316666666667,  45.46555],
  [9.189741666666666,  45.46562222222222],
  [9.185799999999999,  45.46757222222222]
]

# Calculate the westmost, southmost, eastmost and northmost coordinates.
map_bounds = Geo::Utils.bounds(gps_data)
dimensions = [1280, 960]
viewport   = Geo::Viewport.new(map_bounds, dimensions)

map_bounds          # => [6.9201500000000005, 45.46555, 9.189741666666666, 50.948233333333334]
viewport.bounds     # => [1.021728515625, 44.574817404670306, 15.084228515625, 51.60437164681676]
viewport.dimensions # => [1280, 960]
viewport.width      # => 1280
viewport.height     # => 960
viewport.center     # => [8.054945833333333, 48.206891666666664]
viewport.center_lon # => 8.054945833333333
viewport.center_lat # => 48.206891666666664
viewport.zoom       # => 7

Running examples

One of the examples uses Gnuplot. If you are on OS X and you use Homebrew, you may need to install it via brew install gnuplot --with-x. Also check the dependecy gems like k_means_pp and exifr.

$ cd examples
$ ruby simple.rb
$ ruby mapbox.rb
$ ruby mapbox_with_clusters.rb

Installation

Add this line to your application's Gemfile:

gem 'geo', git: 'https://github.com/ollie/geo-mercator.git'

And then execute:

$ bundle

Development

After checking out the repo, run bin/setup to install dependencies. Then, run bin/console for an interactive prompt that will allow you to experiment.

Contributing

  1. Fork it (https://github.com/ollie/geo-mercator/fork)
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request