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https://github.com/3liz/proj4rs

Rust adaptation of Proj4
https://github.com/3liz/proj4rs

Last synced: 3 months ago
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Rust adaptation of Proj4

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README 

        
[![Crates.io](https://img.shields.io/crates/d/proj4rs)](https://crates.io/crates/proj4rs)

[![Documentation](https://img.shields.io/badge/Documentation-Published-green)](https://docs.rs/proj4rs/latest/proj4rs/)

[![Demo](https://img.shields.io/badge/Demo-Published-green)](https://docs.3liz.org/proj4rs/)



---



Rust library for transforming geographic point coordinates

from one coordinate system to another.

This is a pure Rust implementation

of the [PROJ.4 project](https://proj.org/en/9.2/faq.html#what-happened-to-proj-4).



The documentation is available on [docs.rs](https://docs.rs/proj4rs/) and the demo on [docs.3liz.org](https://docs.3liz.org/proj4rs/).



# Features and Limitations



- The aim of Proj4rs is to provide the same functionality as the

[proj4js library](https://github.com/proj4js/proj4js).

- This port implements the PROJ.4 API,

which means there's no 3D/4D/orthometric transformation ATM.

- The goal of Proj4rs is not to be a replacement of PROJ,

but instead being a lightweight implementation of transformations

from CRS to CRS that could be used in Rust and WASM environments.

- This crate does not provide support for WKT. Instead,

there is a dedicated crate for transforming WKT strings to proj string.

- It aims to be WASM compatible for the `wasm32-unknown-unknown` target.

- No installation of external C libraries such as `libproj` or `sqlite3` is needed.



## Basic usage in Rust



Define the coordinate system with proj strings and use the `transform` function.

You can easily get the projection string of any coordinate system

from [EPSG.io](https://epsg.io/).



**Note**: Proj4rs use *radians* as natural angular unit (as does the original proj library)



Example:



```rust

use proj4rs;

use proj4rs::proj::Proj;



// EPSG:5174 - Example

let from = Proj::from_proj_string(concat!(

    "+proj=tmerc +lat_0=38 +lon_0=127.002890277778",

    " +k=1 +x_0=200000 +y_0=500000 +ellps=bessel",

    " +towgs84=-145.907,505.034,685.756,-1.162,2.347,1.592,6.342",

    " +units=m +no_defs +type=crs"

))

.unwrap();



// EPSG:4326 - WGS84, known to us as basic longitude and latitude.

let to = Proj::from_proj_string(concat!(

    "+proj=longlat +ellps=WGS84",

    " +datum=WGS84 +no_defs"

))

.unwrap();



let mut point_3d = (198236.3200000003, 453407.8560000006, 0.0);

proj4rs::transform::transform(&from, &to, &mut point_3d).unwrap();



// Note that WGS84 output from this library is in radians, not degrees.

point_3d.0 = point_3d.0.to_degrees();

point_3d.1 = point_3d.1.to_degrees();



// Output in longitude, latitude, and height.

println!("{} {}",point_3d.0, point_3d.1); // 126.98069676435814, 37.58308534678718

```



## WKT support



If you need full support for WKT, please rely on `proj` which provides

a great implementation of the standards.



If you want WKT support in WASM, please have a look at:



- https://github.com/3liz/proj4wkt-rs

- https://github.com/frewsxcv/crs-definitions



## Grid shift supports 



Nadgrid support is still experimental.

Currently, only Ntv2 multi grids are supported for native build and WASM.



## JavaScript API



When compiled for WASM, the library exposes JavaScript API

that is very similar to that of proj4js.

A thin JavaScript layer provides full compatibility with proj4js

and thus can be used as a proj4js replacement.



Example:



```javascript

let from = new Proj.Projection("+proj=latlong +ellps=GRS80");

let to = new Proj.Projection("+proj=etmerc +ellps=GRS80");

let point = new Proj.Point(2.0, 1.0, 0.0);



// Point is transformed in place

Proj.transform(from, to, point);

```



## Compiling for WASM



Install [wasm-pack](https://rustwasm.github.io/wasm-pack/book/)



```bash

wasm-pack build --target web --no-default-features

```



Or if you have installed [cargo-make](https://sagiegurari.github.io/cargo-make/), use the following

command:



```bash

cargo make wasm

```



### Running the WASM example



There is a [`index.html`] file for testing the WASM module in a navigator.



For security reasons, you need to run it from a server. 

You can start a Python server with the following command:



```bash

python3 -m http.server

```

 

The server will automatically serve the `index.html` file in the current directory.



## Build for npm



```

cargo make wasm_bundle

```



This will create a npm bundler package in pkg-bundler