Geo
Geospatial primitives, algorithms, and utilities for Crystal.
Installation
Add this to your application's shard.yml:
dependencies:
geo:
github: geocrystal/geoRun shards install
Usage
A Geo::Coord is a point in geographical coordinates: latitude and longitude.
require "geo"
c = Geo::Coord.new(50.004444, 36.231389)
c.strfcoord(%{%latd %latm' %0.1lats" %lath, %lngd %lngm' %0.1lngs" %lngh})
# => "50 0' 16.0" N, 36 13' 53.0" E"
c.strfcoord("%lat,%lng")
# => "-50.004444,-36.231389"
c.to_s
# => "50°0'16"N 36°13'53"E"
pos = Geo::Coord.new(50.004444, 36.231389)
pos.geohash
# => "ubcu2rnbuxcx"
pos.geohash(5)
# => "ubcu2"Polygon
A polygon represents an area enclosed by a closed path (or loop), which is defined by a series of coordinates.
require "geo"
pos1 = Geo::Coord.new(45.3142533036254, -93.47527313511819)
pos2 = Geo::Coord.new(45.31232182518015, -93.34893036168069)
pos3 = Geo::Coord.new(45.23694281999268, -93.35167694371194)
pos4 = Geo::Coord.new(45.23500870841669, -93.47801971714944)
polygon = Geo::Polygon.new([pos1, pos2, pos3, pos4])The Polygon in the example above consists of four sets of Geo::Coord coordinates, but notice that the first and last sets define the same location, which completes the loop. In practice, however, since polygons define closed areas, you don't need to specify the last set of coordinates. Ot will automatically complete the polygon by connecting the last location back to the first location.
The following example is identical to the previous one, except that the last Geo::Coord is omitted:
require "geo"
pos1 = Geo::Coord.new(45.3142533036254, -93.47527313511819)
pos2 = Geo::Coord.new(45.31232182518015, -93.34893036168069)
pos3 = Geo::Coord.new(45.23694281999268, -93.35167694371194)
polygon = Geo::Polygon.new([pos1, pos2, pos3])Additional actions:
coord_inside = Geo::Coord.new(45.27428243796789, -93.41648483416066)
coord_outside = Geo::Coord.new(45.45411010558687, -93.78151703160256)
polygon.contains?(coord_inside) # => true
polygon.contains?(coord_outside) # => false
polygon.centroid # => Geo::Coord(@lat=45.27463866133501, @lng=-93.41400121829719)Additionally you can initialize polygon as convex hull from coordinates of points.
points = [
{1.0, 1.0},
{1.0, 0.0},
{1.0, -1.0},
{0.0, -1.0},
{-1.0, -1.0},
{-1.0, 0.0},
{-1.0, 1.0},
{0.0, 1.0},
{0.0, 0.0},
].map { |point| Geo::Coord.new(point[0], point[1]) }
polygon = Geo::Polygon.new(points, convex_hull: true)
polygon.coords
# => {-1.0, -1.0}, {1.0, -1.0}, {1.0, 1.0}, {-1.0, 1.0}, {-1.0, -1.0}The convex hull is computed using the convex_hull library.
Formatting
Geo::Coord#strfcoord formats coordinates according to directives.
Each directive starts with % and can contain some modifiers before its name.
Acceptable modifiers:
- unsigned integers: none;
- signed integers:
+for mandatory sign printing; - floats: same as integers and number of digits modifier, like
0.3.
List of directives:
| Directive | Description |
|---|---|
%lat |
Full latitude, floating point, signed |
%latds |
Latitude degrees, integer, signed |
%latd |
Latitude degrees, integer, unsigned |
%latm |
Latitude minutes, integer, unsigned |
%lats |
Latitude seconds, floating point, unsigned |
%lath |
Latitude hemisphere, "N" or "S" |
%lng |
Full longitude, floating point, signed |
%lngds |
Longitude degrees, integer, signed |
%lngd |
Longitude degrees, integer, unsigned |
%lngm |
Longitude minutes, integer, unsigned |
lngs |
Longitude seconds, floating point, unsigned |
%lngh |
Longitude hemisphere, "E" or "W" |
Examples:
g = Geo::Coord.new(50.004444, 36.231389)
g.strfcoord('%+lat, %+lng')
# => "+50.004444, +36.231389"
g.strfcoord("%latd°%latm'%lath -- %lngd°%lngm'%lngh")
# => "50°0'N -- 36°13'E"strfcoord handles seconds rounding implicitly:
pos = Geo::Coord.new(0.033333, 91.333333)
pos.strfcoord('%latd %latm %0.5lats') # => "0 1 59.99880"
pos.strfcoord('%latd %latm %lats') # => "0 2 0"Calculate distances between two coords
Haversine formula from haversine shard is used.
require "geo"
require "geo/distance"
london = Geo::Coord.new(51.500153, -0.126236)
new_york = Geo::Coord.new(40.714268, -74.005974)
new_york.distance(london).to_kilometers
# => 5570.4744596620685Contributing
- Fork it (https://github.com/geocrystal/geo/fork)
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create a new Pull Request
Contributors
- Anton Maminov - creator and maintainer