Snyder Map Projection Implementation

Copyright (C) 2012-2014 Jeremy J. Gibbons

Description

Snyder is a map projection library implementing Snyder's seminal USGS projection text including all fiducial appendix values for testing. The code is written in Java and runs on Android. The core library code has no 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(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 lib + resources directories contain the libraries, projection and ellipsoid configuration parameter files necessary to run only the test drivers. When creating a distribution jar file (e.g. snyder-*.jar) from the build system, it is not necessary to include anything from either of the above directories.

Fiducial values file: resources / json / Fiducials.json

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

SnyderVis data provided by:

A Global Self-consistent, Hierarchical, High-resolution Geography Database
http://www.soest.hawaii.edu/pwessel/gshhg
Extracted from version 2.3.0 on 1 February 2014