jmaps

jMaps

jMaps is a light Javascript API for reading Natural Earth's DB files. jMaps provides methods to extract data from the database and creates GeoJSON and XML SVG outputs.

Usage

Extract data and create a GeoJSON object

var jMaps = require('jmaps');

// Create the object
const jmap = jMaps();

// Load the Natural Earth database:
jmap.load('<path>, <ne_110m_admin_0_countries>')

// Get a collection of maps (FeatureCollection)
const maps = jmap.getCollection();

// Get a map (Feature)
const map = jmap.getFeature('feature number');

The GeoJSON object looks like:

{
  bbox: [ ... ],
  type: 'FeatureCollection',
  features: [
    { type: 'Feature', properties: [Object], geometry: [Object] },
    ...
    { type: 'Feature', properties: [Object], geometry: [Object] }
  ]
}

A Feature looks like:

{
  type: 'Feature',
  properties: { ... },
  geometry : {
    type: 'Polygon'
    coordinates: [ ... ]
  }

Nota:

A Natural Earth's database is a folder that contains, at least, two files having the same name as the folder and with the suffix .dbf and .shp. For instance, Natural Earth's database ne_50m_admin_0_countries must contains the two files: ne_50m_admin_0_countries.dbf and ne_50m_admin_0_countries.shp.

Create an XML SVG file

const fs = require('fs');
const jMaps = require('jmaps');

const jmap = jMaps();
jmap.load('<path>, <ne_110m_admin_0_countries>')

// Transform the longitudes and latitudes, from a collection, to x, y plane coordinates
const map = jmap.transform({scale: 1, projection: 'mercator', mirror: 'x'});

// Create a File stream
const fd = fs.createWriteStream('path/to/svg/file', {flags: 'w'});

// Fill the write stream
jmap.toSVG(map, fs);

It creates an XML file that looks like:

<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <g transform="translate(0, 0) scale(1, 1)">
    <path id="" class="land" d="...."></path>
  </g>
</svg>

A Feature produces an XML SVG file with one path while a FeatureCollection produces an XML SVG file with a multitude of paths.

You can enrich your XML files with information extracted from the property properties of a Feature object.

API

This module implements four methods:

• getFeature(feature number),
• getCollection(),
• transform(options),
• toSVG(GeoJSON object, write file stream).

getFeature(n)

This method extracts one Feature from Natural Earth's database and returns a Javascript GeoJSON object.

This method requires one argument. Its is a number - the Feature number. It starts from 1.

getCollection()

This method extracts a FeatureCollection from Natural Earth's database and returns a Javascript GeoJSON object. A FeatureCollection is a set of Feature.

transform(options)

This methods converts the longitude and latitude coordinates of the GeoJSON object to x, y plane coordinates. It returns the transformed Javascript GeoJSON object.

This methods extracts a collection from the loaded database, converts it and returns the converted GeoJSON object.

The options argument is optional. If nothing is provided, the default options are:

{ scale: 1, projection: none, mirror: 'none' }

scale can be any number from 1 to 'infinity'.

projection can be none or mercator.

mirror can be none, x, y, xy.

toSVG(GeoJSON, fd)

This method generates XML SVG data from a collection or a transformed collection.

This method requires two arguments. A GeoJSON object (collection) and fd, a file write stream handler.

License

MIT.