Crate geodesy

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§Geodesy

§Abstract

Rust Geodesy is - unsurprisingly - a geodesy library written in the Rust programming language.

Rust Geodesy provides a number of features to support a number of objectives.

The most important features are

a set of more than 30 geodetic transformation primitives
a set of more than 40 primitives for operations on the ellipsoid
a means for composing these primitives into more complex operations.

The most important objectives are

to support new, and hopefully better, abstractions,
to use these abstractions to build better, simpler, and more tractable, geospatial standards, transformations, and software.

If any of this resonates with you, read on after this minimal usage example…

§Usage

Initialize a new project, using Geodesy:

$ cargo new foo
     Created binary (application) `foo` package

$ cd foo
$ cargo add geodesy

Then overwrite the contents of the foo/src/main.rs file with this: A minimal example, computing the UTM coordinates of some Scandinavian capitals

use geodesy::prelude::*;

fn main() -> Result<(), Box<Error>> {
    let mut context = Minimal::new();
    let utm33 = context.op("utm zone=33")?;

    let cph = Coor2D::geo(55., 12.); // Copenhagen
    let sth = Coor2D::geo(59., 18.); // Stockholm
    let mut data = [cph, sth];

    context.apply(utm33, Fwd, &mut data)?;
    println!("{:?}", data);
    Ok(())
}

and try it out:

$ cargo r
    Finished dev [unoptimized + debuginfo] target(s) in 0.11s
     Running `C:\FLOW\AD\RG\foo\target\debug\foo.exe`

[Coor2D([308124.36786033923, 6098907.825005002]), Coor2D([672319.9640879404, 6543920.334127973])]

§Concrete

Rust Geodesy (RG), is a platform for experiments with geodetic software, transformations, and standards. RG vaguely resembles the PROJ transformation system, and was built in part on the basis of experiments with alternative data flow models for PROJ. The fundamental transformation functionality of RG is fairly complete (i.e. on par with the datum shift/reference frame transformation capability of PROJ), while the number of projections supported is a far cry from PROJ’s enormous gamut. It does, however, support a suite of the most important ones:

Transverse Mercator
Universal Transverse Mercator (UTM)
Web Mercator
Mercator
Oblique Mercator
Lambert Conformal Conic
Lambert Azimuthal Equal Area

But fundamentally, RG is born as a geodesy, rather than a cartography library. And while PROJ benefits from four decades of reality hardening, RG, being a platform for experiments, does not have operational robustness as a main focus. Hence, viewing RG as another PROJ, or PROJ RiiR, will lead to bad disappointment. At best, you may catch a weak mirage of a potential shape of jazz to come for the PROJ internal dataflow.

That said, being written in Rust, with all the memory safety guarantees Rust provides, RG by design avoids a number of pitfalls that are explicitly worked around in the PROJ code base. So the miniscule size of RG compared to PROJ is not just a matter of functional pruning. It is also a matter of development using a tool wonderfully suited for the task at hand.

Also, having the advantage of learning from PROJ experience, both from a user’s and a developer’s perspective, RG is designed to be significantly more extensible than PROJ. So perhaps for a number of applications, and despite its limitations, RG may be sufficient, and perhaps even useful.

§Aims

Dataflow experimentation is just one aspect of RG. Overall, the aims are (at least) fourfold:

Support experiments for evolution of geodetic standards.
Support development of geodetic transformations.
Hence, provide easy access to a number of basic geodetic operations, not limited to coordinate operations.
Support experiments with data flow and alternative abstractions. Mostly as a tool for aims (1, 2, 3)

All four aims are guided by a wish to amend explicitly identified shortcomings in the existing geodetic system landscape.

§Documentation

The documentation is currently limited, but take a look at:

The coordinate operator documentation
The description of kp, the Rust Geodesy coordinate processing program
This essayistic rumination, outlining the overall philosophy and architecture of Rust Geodesy, and this related comparison between PROJ and RG
The API documentation at Docs.rs
The examples
The tests embedded in the source code
This rather concrete and this more philosophical description of the main discrepancy between geodesy and geomatics, RG tries to elucidate and amend.

§Geodesy & friends

Corey Farwell provides the crates geo-geodesy and crs-definitions which greatly facilitate the interoperability between Geodesy and the geo crate of the GeoRust ecosystem.

§License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or here)
MIT license (LICENSE-MIT or here)

at your option.

§Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Modules§

authoring: Extended prelude for authoring Contexts and InnerOp modules
coord: Coordinate related elements
ctx: Context related elements
ellps: Ellipsoid related elements
prelude: The bread-and-butter, shrink-wrapped and ready to use

Enums§

Bibliography: Some literature, that has been useful in designing and implementing this library.
Direction: Fwd: Indicate that a two-way operator, function, or method, should run in the forward direction. Inv: Indicate that a two-way operator, function, or method, should run in the inverse direction.
Error: The Rust Geodesy error messaging enumeration. Badly needs reconsideration

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