https://github.com/perliedman/local-proj

Find a suitable local projection from GeoJSON data
https://github.com/perliedman/local-proj

Last synced: about 1 month ago
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Find a suitable local projection from GeoJSON data

• Host: GitHub
• URL: https://github.com/perliedman/local-proj
• Owner: perliedman
• License: isc
• Created: 2015-09-28T07:11:38.000Z (about 9 years ago)
• Default Branch: master
• Last Pushed: 2017-04-05T19:17:37.000Z (over 7 years ago)
• Last Synced: 2024-04-26T07:22:53.169Z (7 months ago)
• Language: JavaScript
• Size: 7.81 KB
• Stars: 3
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.txt

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README

        
# local-proj

[![npm version](https://badge.fury.io/js/local-proj.svg)](https://badge.fury.io/js/local-proj) [![Build status](https://travis-ci.org/perliedman/local-proj.svg?branch=master)](https://travis-ci.org/perliedman/local-proj)

Find a projection for easy cartesian calculations, given a GeoJSON in WGS84.

_Problem:_ you have geographic data in WGS84 of limited extent, but arbitrary location,

and you need to work with the data in a cartesian system (use euclidean distance, etc.)

_Solution:_ feed your data to `local-proj`, and it will hand you a suitable projection

independent of geographic location

## Installing

```

npm install --save local-proj

```

## Example

```javascript

var localProj = require('local-proj');

var geojson = [...]

var projection = localProj.find(geojson);

var cartesian = projection.forward(geojsoncoord);

```

To reproject your GeoJSON to the projection, you might want to look at

[reproject](https://github.com/perliedman/reproject).

## API

### find(geojson)

Finds a local projection that is suitable for projecting the `geojson` to cartesian

coordinates.

The returned projection is a [proj4](http://proj4js.org/) projection object (`proj4.Proj`), which

you can use to create transforms to and from other projections.

Note that the local coordinate system will only work as expected for datasets up to a couple

of hundred kilometers in size.

Currently, the returned projection will always be a [transverse mercator](https://en.wikipedia.org/wiki/Transverse_Mercator_projection) projection.