simple-meshcode

A Ruby library to calculate Japan Standard Regional Mesh (JIS X 0410).

Supports mesh levels 1 through 6 with a C extension for fast encoding/decoding.

This library covers only a subset of JIS X 0410. It does not support doubled (2-bai) mesh, quintupled (5-bai) mesh, or other extended mesh types defined in the standard.

Installation

gem install simple-meshcode

Or build from source:

cd ext && ruby extconf.rb && make && cd ..

Usage

require 'simple-meshcode'

API

Meshcode.meshcode(lat, lon, level) -> String

Encodes latitude/longitude to a meshcode string.

• lat (Numeric) -- latitude in degrees
• lon (Numeric) -- longitude in degrees (100..200)
• level (Integer) -- mesh level 1..6

Meshcode.meshcode(35.6809, 139.7673, 1)  #=> "5339"
Meshcode.meshcode(35.6809, 139.7673, 3)  #=> "53394611"

Meshcode.meshpoint(meshcode, yoffset=0, xoffset=0) -> [lat, lon]

Decodes a meshcode to latitude/longitude. Offsets (0.0 to 1.0) specify position within the mesh cell (0,0 = SW corner, 1,1 = NE corner).

• meshcode (String) -- meshcode string
• yoffset (Numeric) -- latitude offset (default: 0)
• xoffset (Numeric) -- longitude offset (default: 0)

Meshcode.meshpoint("53394611")           #=> [35.675, 139.7625]
Meshcode.meshpoint("53394611", 0.5, 0.5) #=> [35.67916667, 139.76875]

Meshcode.meshlevel(meshcode) -> Integer

Returns the mesh level inferred from the meshcode length.

Meshcode.meshlevel("5339")        #=> 1
Meshcode.meshlevel("53394611324") #=> 6

Meshcode.meshcode_and_offset(lat, lon, level) -> [meshcode, yoffset, xoffset]

Encodes to a meshcode and returns the offset (0.0 to 1.0) within the mesh cell.

Meshcode.meshcode_and_offset(35.6809, 139.7673, 3)
#=> ["53394611", 0.708..., 0.384...]

Meshcode.meshinfo(meshcode) -> Hash

Returns a hash containing mesh metadata.

Meshcode.meshinfo("53394611")
#=> {
#     "level"    => 3,
#     "meshcode" => "53394611",
#     "dy"       => 0.00833...,
#     "dx"       => 0.0125,
#     "lat0"     => 35.675,
#     "lon0"     => 139.7625,
#     "lat1"     => 35.68333...,
#     "lon1"     => 139.775,
#     "latc"     => 35.67916...,
#     "lonc"     => 139.76875,
#     "polygon"  => [[139.7625, 35.675], ...]
#   }

Mesh Levels

Level	Name	Lat span	Lon span	Code digits
1	Primary area partition	40'	1 deg	4
2	Secondary area partition	5'	7'30"	6
3	Standard area partition	30"	45"	8
4	Half partition	15"	22.5"	9
5	Quarter partition	7.5"	11.25"	10
6	Eighth partition	3.75"	5.625"	11

License

MIT