@the-data-center/geojson-data-link v0.1.0

GeoJSON Data Link

A NodeJS library to link properties on two different GeoJSON files by determining if a geographic point is within a larger geographic region and linking the metadata.

Installation

It's not on NPM just yet but here's how it will work shortly:

npm install geojson-data-link

or

yarn install geojson-data-link

About The Data Center

The Data Center of Southeast Louisiana is a fully independent, data-focused non-profit with a mission to build prosperous, inclusive, and sustainable communities by making informed decisions possible. If you find this tool useful, please visit our web site to learn more about our work and consider supporting us in our mission.

Usage

Command Line Interface

The command line version accepts as arguments the two geojson files and the fields you want to merge. It returns your new, merged file to stdout. (If you don't work with the CLI often, you can append > filename.geojson to the command to save the output to a file instead of display it in the terminal.)

The long example might be:

npx geojson-data-link --coordinatesfile ~/geography/nola-library-locations.geojson --polyfile ~/geography/la-census-track.geojson --fields GEOID,STATEFP > ~/geography/libraries-with-new-data.geojson

This is equivalent to:

npx geojson-data-link -c ~/geography/nola-library-locations.geojson -p ~/geography/la-census-track.geojson -f GEOID,STATEFP > ~/geography/libraries-with-new-data.geojson

Here's the options:

Options:
  --version              Show version number                           [boolean]
  -p, --polyfile         GeoJSON file with Polygons and GEOID in the properties
  -c, --coordinatesfile  GeoJSON with coordinates/points to be given correct
                         GEOID. (If it has polygons, the centroid will be used)
  -f, --fields           Comma separated fields to match (default: GEOID)
  -h, --help             Show help                                     [boolean]

As a Library

const match = require('./matchGEOID').matchGEOID;
const polyfile = '~/geography/census-track.geojson';
const coordinatesfile = '~/geography/library-locations.geojson';

match({
  polyfile: polyfile,
  coordinatesfile: coordinatesfile,
  fields: ["GEOID","STATEFP","COUNTYFP","TRACTCE"],
  sync: false
}, function(err, asyncCoordsFile) {
  if (err) console.error(err);
  else console.log(JSON.stringify(asyncCoordsFile));
});

Your options are:

• polyfile: the geojson file with your polygon features (i.e., regions to check)
• coordinatesfile: the geojson file with your point/coordinate features
• fields: an array of fields to copy over after linking
• sync: whether the command to get the files runs asynchronously or synchronously.

If you set sync: true, be warned that it will block I/O while it fetches the (potentially large) files. It's faster for one-off scripts but is not recommended for larger projects.