Oblique Mercator Transformer for geo::Geometry Types

Convert geo types between geodesic degrees and cartesian meters using Oblique Mercator.

This uses the Oblique Mercator projection to define arbitrary zero points (0, 0) on the globe, making deformation near that point negligible; and at the same time converting the units to meters, that allows for precise measurements of distances and areas.

Under the hood this uses the geodesy crate for the projection calculation of each coordinate, but with an ergonomic wrapper to handle full geo::Geometry types (points, lines, polygons, etc).

Usage

Installation:

$ cargo add geo-omerc

OMercTransformer methods:

• new(): creates a new transformer with a geodesic anchor point defined as the new cartesian center.
• to_cartesian(): converts geometries with geodesic coordinates (in degrees) into ones with cartesian coordinates (in meters).
• to_geodesic(): converts geometries with cartesian coordinates (in meters) into ones with geodesic coordinates (in degrees).

This uses a struct with methods instead of just functions to cache the operation definition, that, once created, could be reused to transform many geometries. The two transformation methods handle geo::Geometry as both input and output (wrapped in a Result).

Examples

use geo::{Point, polygon, Distance, Euclidean, Area};
use geo_omerc::OMercTransformer;

let coliseum = Point::new(12.49233, 41.89018);
let pantheon = Point::new(12.47683, 41.89856);

// Defines a transformer with the Coliseum as the center (0, 0):
let transformer = OMercTransformer::new(&coliseum).unwrap();


// Roundtrip: --------------------------------------------------------

let pantheon_m = transformer.to_cartesian(&pantheon.into()).unwrap();
println!("{:?}", pantheon_m);
// POINT(-1286.2243529009943 930.893116932613) -> in meters.

let pantheon_d = transformer.to_geodesic(&pantheon_m.into()).unwrap();
println!("{:?}", pantheon_d);
// POINT(12.476829999999996 41.8985600000268) -> in degrees.


// Distance: ---------------------------------------------------------

let coliseum_m = transformer.to_cartesian(&coliseum.into()).unwrap();
let pantheon_m = transformer.to_cartesian(&pantheon.into()).unwrap();
let distance = Euclidean.distance(&coliseum_m, &pantheon_m);
println!("{}", distance);
// 1587.7452822004639 -> in meters.


// Area: -------------------------------------------------------------

let circus_maximus = polygon![
    (x: 12.4833, y: 41.8881),
    (x: 12.4823, y: 41.8872),
    (x: 12.4879, y: 41.8838),
    (x: 12.4891, y: 41.8849),
    (x: 12.4833, y: 41.8881),
];
let circus_maximus_m = transformer.to_cartesian(&circus_maximus.into()).unwrap();
println!("{}", circus_maximus_m.unsigned_area());
// 86010.79776633419 -> in square meters.