#encoding #polyline #pair #precision #triple #list #representation

bin+lib flexpolyline

Flexible Polyline encoding: a lossy compressed representation of a list of coordinate pairs or triples

1 unstable release

0.1.0 Apr 28, 2020

#309 in Compression

Download history 2121/week @ 2023-11-23 2224/week @ 2023-11-30 2916/week @ 2023-12-07 1851/week @ 2023-12-14 745/week @ 2023-12-21 795/week @ 2023-12-28 1840/week @ 2024-01-04 2175/week @ 2024-01-11 1768/week @ 2024-01-18 2050/week @ 2024-01-25 2505/week @ 2024-02-01 2688/week @ 2024-02-08 2850/week @ 2024-02-15 2890/week @ 2024-02-22 2564/week @ 2024-02-29 1234/week @ 2024-03-07

10,067 downloads per month

MIT license

34KB
754 lines

Flexible Polyline encoding

The flexible polyline encoding is a lossy compressed representation of a list of coordinate pairs or coordinate triples. It achieves that by:

  1. Reducing the decimal digits of each value.
  2. Encoding only the offset from the previous point.
  3. Using variable length for each coordinate delta.
  4. Using 64 URL-safe characters to display the result.

The encoding is a variant of Encoded Polyline Algorithm Format. The advantage of this encoding over the original are the following:

  • Output string is composed by only URL-safe characters, i.e. may be used without URL encoding as query parameters.
  • Floating point precision is configurable: This allows to represent coordinates with precision up to microns (5 decimal places allow meter precision only).
  • It allows to encode a 3rd dimension with a given precision, which may be a level, altitude, elevation or some other custom value.

Specification

See Specification.

Example

use flexpolyline::{Polyline, Precision};

// encode
let coordinates = vec![
    (50.1022829, 8.6982122),
    (50.1020076, 8.6956695),
    (50.1006313, 8.6914960),
    (50.0987800, 8.6875156),
];

let polyline = Polyline::Data2d {
    coordinates,
    precision2d: Precision::Digits5,
};

let encoded = polyline.encode().unwrap();
assert_eq!(encoded, "BFoz5xJ67i1B1B7PzIhaxL7Y");

// decode
let decoded = Polyline::decode("BFoz5xJ67i1B1B7PzIhaxL7Y").unwrap();
assert_eq!(
    decoded,
    Polyline::Data2d {
        coordinates: vec![
            (50.10228, 8.69821),
            (50.10201, 8.69567),
            (50.10063, 8.69150),
            (50.09878, 8.68752)
        ],
        precision2d: Precision::Digits5
    }
);

No runtime deps