proj-rust

Pure-Rust coordinate transformation library. No C libraries, no build scripts, no unsafe code.

This workspace currently contains:

• proj-core: transform engine, CRS registry, projection math, and datum shifts
• proj-wkt: parsing and compatibility helpers for EPSG codes, WKT, PROJ strings, and PROJJSON

Release Scope

proj-rust is intended for production use within its supported CRS and projection set. It is not a full implementation of all PROJ capabilities.

Current non-goals for v0.1.0 include:

• grid-shift based datum transforms
• vertical or time-dependent CRS operations
• full PROJ pipeline semantics and operation selection by area of use
• complete axis-order and unit-model coverage across arbitrary CRS definitions

Usage

use proj_core::{Bounds, Transform};

// WGS84 geographic (degrees) -> Web Mercator (meters)
let t = Transform::new("EPSG:4326", "EPSG:3857").unwrap();
let (x, y) = t.convert((-74.006, 40.7128)).unwrap();

// Inverse: Web Mercator -> WGS84
let inv = t.inverse().unwrap();
let (lon, lat) = inv.convert((x, y)).unwrap();

// Works with geo_types::Coord<f64> (with `geo-types` feature)
let coord = geo_types::Coord { x: -74.006, y: 40.7128 };
let projected: geo_types::Coord<f64> = t.convert(coord).unwrap();

// Batch transforms (parallel with `rayon` feature)
let coords: Vec<(f64, f64)> = vec![(-74.006, 40.7128); 1000];
let results = t.convert_batch_parallel(&coords).unwrap();

// 3D transforms preserve the third ordinate unchanged
let (x, y, h) = t.convert_3d((-74.006, 40.7128, 15.0)).unwrap();
assert_eq!(h, 15.0);

// Reproject an extent by densifying its perimeter
let bounds = Bounds::new(-74.3, 40.45, -73.65, 40.95);
let projected_bounds = t.transform_bounds(bounds, 8).unwrap();
assert!(projected_bounds.max_x > projected_bounds.min_x);

Coordinates use the CRS's native units: degrees for geographic CRS, meters for projected CRS. For convert_3d(), the z component is preserved unchanged because the current CRS model is horizontal-only.

Supported Input Formats

With proj-core, transforms can be created from registry-backed EPSG codes such as "EPSG:4326" and "EPSG:3857".

With proj-wkt, the following CRS definition formats are supported:

• EPSG authority codes and bare EPSG numbers
• OGC CRS:84 aliases and EPSG URNs
• common PROJ strings for the implemented projection families, including legacy +init=epsg:XXXX
• WKT1 and the supported WKT2 projected/geographic CRS forms, including top-level EPSG ID[...]
• basic PROJJSON geographic and projected CRS definitions for the implemented methods

Supported CRS

Custom CRS definitions can be constructed and passed to Transform::from_crs_defs(). The companion proj-wkt crate parses EPSG codes, a subset of WKT/PROJ strings, and basic PROJJSON inputs into CrsDef values.

Compatibility Surface

proj-wkt also exposes a lightweight Proj compatibility facade for downstream code that currently uses the common new_known_crs / new / create_crs_to_crs_from_pj / convert flow. It is intentionally narrow and only covers the supported CRS semantics in this workspace.

proj-core::Transform and proj-wkt::Proj also expose inverse-transform construction and sampled bounds reprojection via inverse() and transform_bounds().

Feature Flags

Testing

cargo test                        # all tests
cargo test -p proj-core --no-default-features  # core crate without rayon/geo-types
./scripts/run-reference-parity.sh
cargo clippy --all-targets -- -D warnings
cargo package -p proj-core --allow-dirty

For reference comparisons and current benchmark results against bundled C PROJ, see docs/benchmark-report.md.

Publishing

Release this workspace as a 0.x line with scoped claims: production-ready for the supported projection families and CRS formats above, but not a claim of full PROJ parity.

Publish order matters because proj-wkt depends on proj-core as a separately published crate:

cargo package -p proj-core --allow-dirty
cargo publish -p proj-core

# wait for crates.io to index the new proj-core version

cargo package -p proj-wkt --allow-dirty
cargo publish -p proj-wkt

proj-core packages and verifies independently. proj-wkt will not package for upload until the matching proj-core version is available in the crates.io index.

License

MIT OR Apache-2.0