Snyder Geospatial Projection System

Copyright (c) 2012-2021
APIS Point, LLC

Description

Snyder is a geospatial projection library implementing all projections and the appendix fiducial values for unit testing as defined in John P. Snyder's seminal USGS professional paper, Map Projections--A Working Manual.

The library is free and open-source software licensed under The MIT License. Snyder runs on Android, is thread safe, and does not require any external dependencies.

Features

+ Android compatible
+ Thread safe
+ Minimum class topology
+ Small library footprint

Code Example

Stereographic Projection Example

    public static void main(String... args) {
        Projection proj = new Stereographic();
        //
        // WGS 84
        //
        Ellipsoid e = new Ellipsoid(6378137.0, 298.257223563);

        //
        // Print all available parameters (for reference only)
        //
        for(String prop : proj.getDatumProperties())
            System.out.println(prop);

        Datum d = new Datum();

        //
        // Core projection library assumes all long/lat values are in Radians
        //
        d.setUserOverrideProperty("lon0", 0);
        d.setUserOverrideProperty("lat1", 0);
        d.setUserOverrideProperty("k0", 1);

        double[] lon = new double[] {1.0 * SnyderMath.DEG_TO_RAD}; // 1.0 degree
        double[] lat = new double[] {2.0 * SnyderMath.DEG_TO_RAD}; // 2.0 degree

        //
        // [0][] -> x[]
        // [1][] -> y[]
        //
        double[][] forward = proj.forward(lon, lat, e, d);
        System.out.println("x: " + forward[0][0] + ", y: " + forward[1][0]);

        //
        // [0][] -> lon[]
        // [1][] -> lat[]
        //
        double[][] inverse = proj.inverse(forward[0], forward[1], e, d);
        System.out.println(
                "lon: "   + (float) (inverse[0][0] * SnyderMath.RAD_TO_DEG) +
                ", lat: " + (float) (inverse[1][0] * SnyderMath.RAD_TO_DEG));
    }

Test Drivers + Deployment

The src / test / resources directory contains the test data fiducials, projection and ellipsoid configuration parameter files necessary to run only the test drivers.

Fiducial values file: src / test / resources / json / Fiducials.json

Building Snyder

$ gradle build

The resulting directory build contains the built artifacts including the deployment jar file:
build / libs / ap.snyder-{VERSION}.jar

References

Snyder, J. P. Map Projections--A Working Manual.
U. S. Geological Survey Professional Paper 1395.
Washington, DC: U. S. Government Printing Office, 1987, 1994 3rd Printing.
http://pubs.er.usgs.gov/publication/pp1395

A Global Self-consistent, Hierarchical, High-resolution Geography Database^* http://www.soest.hawaii.edu/pwessel/gshhg
Extracted from version 2.3.4 on 1 January 2015

License

Code licensed under the MIT License

_{^{* SnyderVis, GSHHG files will no longer be updated.}}