Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

https://github.com/NAISorg/conrex

An Elixir implementation of the CONREC algorithm for topographic or isochrone maps.
https://github.com/NAISorg/conrex

conrec elixir gis isochrone-map isochrones map topographic-maps topography

Last synced: about 2 months ago
JSON representation

An Elixir implementation of the CONREC algorithm for topographic or isochrone maps.

Lists

README 

        
# Conrex



![Conrex logo](https://github.com/NAISorg/conrex/raw/master/priv/static/logo.png)



![Example output visualization](https://github.com/NAISorg/conrex/raw/master/priv/static/screenshot.png)



The[ National Association of Independent Schools](https://nais.org) developed an Elixir implementation of the [Paul Bourke's Conrec](http://paulbourke.net/papers/conrec/) algorithm to calculate the drive-time to a particular location. The [Conrex hex package](https://hex.pm/packages/conrex) is now available to developers [here on GitHub.](https://github.com/NAISorg/conrex)



Most map-based apps calculate the distance from a central point outward. That’s helpful if you want to see how long it will take you to fly somewhere else, but not so helpful if you want to calculate how long it will take customers to drive through traffic to get to your location.



[Conrex](https://github.com/NAISorg/conrex) uses a convergent isochrone to calculate real traffic and topographic conditions. An implementation of [Paul Bourke's CONREC algorithm in Elixir](http://paulbourke.net/papers/conrec/), [Conrex](https://github.com/NAISorg/conrex) is now available to the open source community.    



NAIS developed Conrex for its [Market View app](https://marketview.nais.org). Market View helps schools find children are within a reasonable driving distance of the school. It can also be used to map bus routes, commute times, or to determine a new location for a business.



## Installation



Conrex can be installed by adding `conrex` to your list of dependencies in

`mix.exs`:



```elixir

def deps do

  [

    {:conrex, "~> 1.0.0"}

  ]

end

```



## Usage



The main algorithm outlined by Bourke can be invoked with `Conrex.conrec`:



```

iex> Conrex.conrec(values, x_coords, y_coords, contour_levels)

```



where `values` is a 2D list of samples (heights, travel times, etc), `x_coords`

and `y_coords` are lists of X and Y coordinates for the sample grid, and

`contour_levels` is a list of values at which a contour should be calculated.

`Conrex.conrec` outputs a list of line segments to match the classic algorithm.



If the X and Y values are GPS coordinates, you can use `Conrex.contour_polygons`

to generate GeoJSON polygons for each contour level:



```

iex> Conrex.contour_polygons(values, x_coords, y_coords, contour_levels, reference_point)

```



The additional parameter, `reference_point`, is a point known to be within the

contour polygon, but outside any polygon holes. When converting the line

segments to GeoJSON `%Geo.Polygon{}`s, Conrex will discard exterior polygon

rings, and correct the coordinate winding for the main ring and the polygon

holes to conform to the [GeoJSON spec](https://tools.ietf.org/html/rfc7946#section-3.1.6).



## Contributing



Pull requests are welcome. For major changes, please open an issue first to

discuss what you would like to change.



Some of the tests will write output and sample data to a `contour.js` file,

which can be used to visualize the test data and result. The visualization can

be seen by viewing `priv/static/index.html` in a web browser.



## Credits



[Zack Michener](https://zjm.me/) & [Stephanie Wilkinson](https://github.com/stephaniewilkinson/)



## License



[MIT](https://choosealicense.com/licenses/mit/)