Google IO 2013 App Mystery Values

Question

I'm trying to make use of the SVGTileProvider that is found in the Google IO 2013 app. I can't figure out exactly how to position an image on the Google Map though. I've narrowed it down to this section of the class. These aren't lat/long coordinates however somehow they must be coming from lat/long coordinates. Does anyone know what these are or where they come from?

mBaseMatrix.setPolyToPoly(
    new float[]{
        0, 0,
        limits.width(), 0,
        limits.width(), limits.height()
    }, 0,
    new float[]{
        40.95635986328125f, 98.94217824936158f,
        40.95730018615723f, 98.94123077396628f,
        40.95791244506836f, 98.94186019897214f
    }, 0, 3);

Update

The first set of mystery numbers roughly translates to lat/long 37.783887,-122.405107.

Update 2

These methods help me convert latitude to a y value and vice versa. How can I do this for X and Longitude?

public static double y2lat(double aY) {
    return Math.toDegrees(2 * Math.atan(Math.exp(Math.toRadians(aY))) - Math.PI / 2);
}
public static double lat2y(double aLat) {
    return Math.toDegrees(Math.log(Math.tan(Math.PI / 4 + Math.toRadians(aLat) / 2)));
}

Is it suppose to be Madrid, Spain? Why arent they lat long values? — IAmGroot, Jan 16 '14 at 16:40
No. I'm currently trying to display an image over a building in Atlanta, GA. After that I'll have a few other locations. — Sababado, Jan 16 '14 at 16:41
I typed it in wrong, but its still not atlanta. Google does take Lat longs to that accuracy though. it turned 40.98 into a long value — IAmGroot, Jan 16 '14 at 16:53

score 6 · Accepted Answer · answered Jan 16 '14 at 22:35

6

Turns out these are World Coordinates.

Here is some java code to translate from lat/long to x/y.

public static float lat2y(double aLat) {
    return (float) (((1 - Math.log(Math.tan(aLat * Math.PI / 180) + 1 / Math.cos(aLat * Math.PI / 180)) / Math.PI) / 2 * Math.pow(2, 0)) * 256);
}
public static float lon2x(double lon) {
    return (float) ((lon + 180f) / 360f * 256f);
}

answered Jan 16 '14 at 22:35

Sababado

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This should be marked as the right answer! Thanks @Sababado :-) – saguinav Jul 26 '14 at 20:07
Extensive and exhaustive Google searching. I couldn't honestly say where I found them now. Probably somewhere when I looked up how to convert world coordinates in Java – Sababado Feb 19 '19 at 18:29

score 1 · Answer 2 · edited May 23 '17 at 12:01

1

See the class TileProjection I posted in the answer to this SO question. If Sababado is right, that the numbers are WorldCoordinates, then this class should help you to convert them. You can find the formulas also here.

edited May 23 '17 at 12:01

Community

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answered Jan 17 '14 at 16:38

user2808624

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Google IO 2013 App Mystery Values

2 Answers2