bug with GeoHashUtils.decode _box

[Lucio Piccoli]

this is a test that illustrates the issue with latitudes for neighbors r7hg9z, r7hg9y

the south lat of 9z and north lat of 9y should be identical since r7hg9z is directly above r7hg9y.
However the north/south latitudes seems to around the wrong away.
the longitudes seem ok.

    @Test
public void shouldDecodeBoxwithSimilarEdge() {
    //north latitude, 0
    //south latitude, 1 
    //east longitude, 2 
    //west longitude, 3

    String geoHashz = "r7hg9z";
    String geoHashy = "r7hg9y";     
    double[] decodedy = decode_bbox(geoHashy);
    double[] decodedz = decode_bbox(geoHashz);

    //se 9z should equal ne 9y
    //south lat of 9z and north lat of 9y
    assertSimilar(decodedz[1], decodedy[0]);
    //north lat of 9z and south lat of 9y
    assertNotSimilar(decodedz[0], decodedy[1]); // should not be the same

    //east lng 
    assertSimilar(decodedz[2], decodedy[2]);
    //west lng
    assertSimilar(decodedz[3], decodedy[3]);


}

[Jilles van Gurp]

copied back mysteriously disappeared comment:

Hi, thanks for reporting. I usually use a simple google maps hack to debug this type of issues. I've added the tool to the repository just now under tools. If I render your circle, I get cluster of geohashes in Brisbane that sort of looks alright. If you bump the geohashlength by one, you can see better what is happening. You'll have to manually paste in the hashes arrays below.

The chunk that appears to be missing would be partially outside the circle and that's why it is omitted. The fix is to use longer geohashes. This will fill the hole with smaller geohashes and it is more clear this way what it is doing.

For reference, here are the two arrays that I generated from your test coordinate:

The first commmented one is the original one and the second one has one character more in the geohash. Just modify the html and open it in a browser to render.

// var hashes=["r7hg9z","r7hgcb","r7hgdj","r7hgdn","r7hgdp","r7hgdq","r7hgdr","r7hgf0","r7hgf1","r7hgf2"];
var hashes=["r7hg9ve","r7hg9vf","r7hg9vg","r7hg9vj","r7hg9vk","r7hg9vm","r7hg9vn","r7hg9vp","r7hg9vq","r7hg9vr","r7hg9vs","r7hg9vt","r7hg9vu","r7hg9vv","r7hg9vw","r7hg9vx","r7hg9vy","r7hg9vz","r7hg9wx","r7hg9wz","r7hg9xp","r7hg9xq","r7hg9xr","r7hg9xw","r7hg9xx","r7hg9xy","r7hg9xz","r7hg9y1","r7hg9y2","r7hg9y3","r7hg9y4","r7hg9y5","r7hg9y6","r7hg9y7","r7hg9y8","r7hg9y9","r7hg9yb","r7hg9yc","r7hg9yd","r7hg9ye","r7hg9yf","r7hg9yg","r7hg9yh","r7hg9yj","r7hg9yk","r7hg9ym","r7hg9yn","r7hg9yp","r7hg9yq","r7hg9yr","r7hg9ys","r7hg9yt","r7hg9yu","r7hg9yv","r7hg9yw","r7hg9yx","r7hg9yy","r7hg9yz","r7hg9z","r7hgc8n","r7hgc8p","r7hgc8r","r7hgc8x","r7hgc8z","r7hgcb","r7hgcc0","r7hgcc1","r7hgcc2","r7hgcc3","r7hgcc4","r7hgcc5","r7hgcc6","r7hgcc7","r7hgcc9","r7hgccd","r7hgcce","r7hgccf","r7hgccg","r7hgcch","r7hgccj","r7hgcck","r7hgccm","r7hgccn","r7hgccp","r7hgccq","r7hgccr","r7hgccs","r7hgcct","r7hgccu","r7hgccv","r7hgccw","r7hgccx","r7hgccy","r7hgccz","r7hgcf5","r7hgcfh","r7hgcfj","r7hgcfm","r7hgcfn","r7hgcfp","r7hgcfq","r7hgcfr","r7hgcfx","r7hgdhb","r7hgdhc","r7hgdhf","r7hgdhg","r7hgdhu","r7hgdhv","r7hgdhy","r7hgdhz","r7hgdj","r7hgdkb","r7hgdm0","r7hgdm1","r7hgdm2","r7hgdm3","r7hgdm4","r7hgdm5","r7hgdm6","r7hgdm7","r7hgdm8","r7hgdm9","r7hgdmb","r7hgdmc","r7hgdmd","r7hgdme","r7hgdmf","r7hgdmg","r7hgdmk","r7hgdms","r7hgdmt","r7hgdmu","r7hgdmv","r7hgdmw","r7hgdmy","r7hgdmz","r7hgdn","r7hgdp","r7hgdq","r7hgdr","r7hgdw2","r7hgdw8","r7hgdw9","r7hgdwb","r7hgdwc","r7hgdx0","r7hgdx1","r7hgdx2","r7hgdx3","r7hgdx6","r7hgdx8","r7hgdx9","r7hgdxb","r7hgdxc","r7hgdxd","r7hgdxf","r7hgf0","r7hgf1","r7hgf2","r7hgf30","r7hgf31","r7hgf32","r7hgf33","r7hgf34","r7hgf35","r7hgf36","r7hgf37","r7hgf38","r7hgf39","r7hgf3b","r7hgf3c","r7hgf3d","r7hgf3e","r7hgf3f","r7hgf3g","r7hgf3h","r7hgf3j","r7hgf3k","r7hgf3m","r7hgf3n","r7hgf3p","r7hgf3q","r7hgf3r","r7hgf3s","r7hgf3t","r7hgf3u","r7hgf3v","r7hgf3w","r7hgf3x","r7hgf3y","r7hgf40","r7hgf41","r7hgf42","r7hgf43","r7hgf44","r7hgf45","r7hgf46","r7hgf47","r7hgf48","r7hgf49","r7hgf4d","r7hgf4e","r7hgf4f","r7hgf4g","r7hgf4h","r7hgf4j","r7hgf4k","r7hgf4m","r7hgf4n","r7hgf4p","r7hgf4q","r7hgf4r","r7hgf4s","r7hgf4t","r7hgf4u","r7hgf4v","r7hgf4w","r7hgf4x","r7hgf4y","r7hgf60","r7hgf61","r7hgf62","r7hgf63","r7hgf64","r7hgf65","r7hgf66","r7hgf67","r7hgf68","r7hgf69","r7hgf6h","r7hgf6j","r7hgf80","r7hgf81","r7hgf82","r7hgf83","r7hgf84","r7hgf88","r7hgf89","r7hgf8b","r7hgf8c","r7hgf90","r7hgf92"];