Crate proj

Coordinate transformation via bindings to the PROJ v7.1.x API.

Two coordinate transformation operations are currently provided: projection (and inverse projection) and conversion.

Projection is intended for transformations between geodetic and projected coordinates and vice versa (inverse projection), while conversion is intended for transformations between projected coordinate systems. The PROJ documentation explains the distinction between these operations in more detail.

This crate depends on libproj v7.1.x, accessed via the proj-sys crate. By default, proj-sys will try to find a pre-existing installation of libproj on your system. If an appropriate version of libproj cannot be found, the build script will attempt to build libproj from source. You may specify a from-source build with the bundled_proj feature.

Out of the box, any (x, y) numeric tuple can be provided as input to proj. You can conform your own types to the Coord trait to pass them in directly and avoid intermediate allocations. There is a geo-types feature, enabled by default, which implements this trait for types in the geo-types crate.

Methods for conversion and projection of slices of Coords are also available.

Examples

Convert from NAD 83 US Survey Feet to NAD 83 Meters Using EPSG Codes

use proj::Proj;

let from = "EPSG:2230";
let to = "EPSG:26946";
let ft_to_m = Proj::new_known_crs(&from, &to, None).unwrap();
let result = ft_to_m
    .convert((4760096.421921f64, 3744293.729449f64))
    .unwrap();
assert_relative_eq!(result.0, 1450880.29, epsilon=1e-2);
assert_relative_eq!(result.1, 1141263.01, epsilon=1e-2);

Convert from NAD 83 US Survey Feet to NAD 83 Meters Using the pipeline Operator

Note that as of v5.0.0, PROJ uses the pipeline operator, which allows an arbitrary number of steps in a conversion. The example below works as follows:

• define the operation as a pipeline operation
• define step 1 as an inverse transform, yielding geodetic coordinates
• define step 2 as a forward transform to projected coordinates, yielding metres.

use proj::Proj;

let ft_to_m = Proj::new("
    +proj=pipeline
    +step +inv +proj=lcc +lat_1=33.88333333333333
    +lat_2=32.78333333333333 +lat_0=32.16666666666666
    +lon_0=-116.25 +x_0=2000000.0001016 +y_0=500000.0001016001 +ellps=GRS80
    +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs
    +step +proj=lcc +lat_1=33.88333333333333 +lat_2=32.78333333333333 +lat_0=32.16666666666666
    +lon_0=-116.25 +x_0=2000000 +y_0=500000
    +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
").unwrap();

// The Presidio, approximately
let result = ft_to_m.convert((4760096.421921f64, 3744293.729449f64)).unwrap();
assert_relative_eq!(result.0, 1450880.29, epsilon=1e-2);
assert_relative_eq!(result.1, 1141263.01, epsilon=1e-2);

Usage

There are two options for creating a transformation:

1. If you don't require additional grids or other customisation:
   • Call Proj::new or Proj::new_known_crs. This creates a transformation instance (Proj)
2. If you require a grid for the transformation you wish to carry out, or you need to customise the search path or the grid endpoint:
   • Create a new ProjBuilder by calling ProjBuilder::new(). It may be modified to enable network downloads, disable the grid, cache or modify search paths;
   • Call ProjBuilder.proj() or ProjBuilder.proj_known_crs(). This creates a transformation instance (Proj)

Note:

1. Both ProjBuilder and Proj implement the Info trait, which can be used to get information about the current state of the PROJ instance;
2. Proj::new() and ProjBuilder::proj() have the same signature;
3. Proj::new_known_crs() and ProjBuilder::proj_known_crs() have the same signature.

Requirements

By default, the crate requires libproj 7.1.x to be present on your system. While it may be backwards-compatible with older PROJ 6 versions, this is neither tested nor supported.

Feature Flags

• geo-types: include trait impls for geo-types. See example.
• pkg_config: enables the use of pkg-config when linking against libproj — note that pkg-config must be available on your system.
• bundled_proj: builds libproj from source bundled in the proj-sys crate. Note that this feature requires Sqlite3 and libtiff to be present on your system.
• network: exposes APIs which, when enabled, can fetch grid data from the internet to improve projection accuracy. See enable_network for details.

Network, Cache, and Search Path Functionality

Grid File Download

proj supports network grid download functionality via the network feature. Network access is disabled by default, and can be activated by passing a true bool to enable_network(). Network functionality status can be queried with network_enabled, and the download endpoint can be queried and set using get_url_endpoint and set_url_endpoint.

Grid File Cache

Up to 300 mb of downloaded grids are cached to save bandwidth: This cache can be enabled or disabled using grid_cache_enable.

Search Path Modification

The path used to search for resource files can be modified using set_search_paths

Conform your own types

If you have your own geometric types, you can conform them to the Coord trait and use proj without any intermediate allocation.

use proj::{Proj, Coord};

struct MyPointOfIntereset {
    lat: f64,
    lon: f64,
}

impl Coord<f64> for MyPointOfIntereset {
    fn x(&self) -> f64 {
        self.lon
    }
    fn y(&self) -> f64 {
        self.lat
    }
    fn from_xy(x: f64, y: f64) -> Self {
        Self { lon: x, lat: y }
    }
}

let donut_shop = MyPointOfIntereset { lat: 34.095620, lon: -118.283555 };

let from = "EPSG:4326";
let to = "EPSG:3309";
let proj = Proj::new_known_crs(&from, &to, None).unwrap();

let result = proj.convert(donut_shop).unwrap();

assert_relative_eq!(result.x(), 158458.67, epsilon=1e-2);
assert_relative_eq!(result.y(), -434296.88, epsilon=1e-2);

Integration with geo-types

If you've enabled the geo-types feature, you can skip allocating an intermediate representation, and pass the geo-types directly.

use proj::Proj;
use geo_types::Point;

let my_point = Point::new(4760096.421921f64, 3744293.729449f64);

let from = "EPSG:2230";
let to = "EPSG:26946";
let nad_ft_to_m = Proj::new_known_crs(&from, &to, None).unwrap();

let result = nad_ft_to_m.convert(my_point).unwrap();

assert_relative_eq!(result.x(), 1450880.29, epsilon=1e-2);
assert_relative_eq!(result.y(), 1141263.01, epsilon=1e-2);

Structs

Area	The bounding box of an area of use
Proj	A coordinate transformation object
ProjBuilder	A PROJ Context instance, used to create a transformation object.
Projinfo	Information about PROJ

Enums

ProjError

Errors originating in PROJ which can occur during projection and conversion

Traits

Coord	A point in two dimensional space. The primary unit of input/output for proj.
Info	Read-only utility methods for providing information about the current PROJ instance