1 | // License: GPL. For details, see LICENSE file.
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2 | package org.openstreetmap.josm.data.coor;
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3 |
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4 | import org.openstreetmap.josm.tools.Utils;
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5 |
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6 | public final class QuadTiling {
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7 |
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8 | private QuadTiling() {
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9 | // Hide default constructor for utils classes
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10 | }
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11 |
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12 | public static final int NR_LEVELS = 24;
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13 | public static final double WORLD_PARTS = 1 << NR_LEVELS;
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14 |
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15 | public static final int TILES_PER_LEVEL_SHIFT = 2; // Has to be 2. Other parts of QuadBuckets code rely on it
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16 | public static final int TILES_PER_LEVEL = 1 << TILES_PER_LEVEL_SHIFT;
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17 | public static final int X_PARTS = 360;
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18 | public static final int X_BIAS = -180;
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19 |
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20 | public static final int Y_PARTS = 180;
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21 | public static final int Y_BIAS = -90;
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22 |
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23 | public static LatLon tile2LatLon(long quad) {
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24 | // The world is divided up into X_PARTS,Y_PARTS.
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25 | // The question is how far we move for each bit being set.
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26 | // In the case of the top level, we move half of the world.
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27 | double xUnit = X_PARTS/2d;
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28 | double yUnit = Y_PARTS/2d;
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29 | long shift = (NR_LEVELS*2L)-2L;
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30 |
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31 | double x = 0;
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32 | double y = 0;
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33 | for (int i = 0; i < NR_LEVELS; i++) {
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34 | long bits = (quad >> shift) & 0x3;
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35 | // remember x is the MSB
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36 | if ((bits & 0x2) != 0) {
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37 | x += xUnit;
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38 | }
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39 | if ((bits & 0x1) != 0) {
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40 | y += yUnit;
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41 | }
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42 | xUnit /= 2;
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43 | yUnit /= 2;
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44 | shift -= 2;
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45 | }
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46 | x += X_BIAS;
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47 | y += Y_BIAS;
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48 | return new LatLon(y, x);
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49 | }
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50 |
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51 | static long lon2x(double lon) {
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52 | long ret = (long) ((lon + 180.0) * WORLD_PARTS / 360.0);
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53 | if (Utils.equalsEpsilon(ret, WORLD_PARTS)) {
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54 | ret--;
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55 | }
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56 | return ret;
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57 | }
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58 |
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59 | static long lat2y(double lat) {
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60 | long ret = (long) ((lat + 90.0) * WORLD_PARTS / 180.0);
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61 | if (Utils.equalsEpsilon(ret, WORLD_PARTS)) {
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62 | ret--;
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63 | }
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64 | return ret;
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65 | }
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66 |
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67 | /**
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68 | * Returns quad tiling index for given coordinates and level.
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69 | *
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70 | * @param lat latitude
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71 | * @param lon longitude
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72 | * @param level level
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73 | *
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74 | * @return quad tiling index for given coordinates and level.
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75 | * @since 6171
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76 | */
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77 | public static byte index(final double lat, final double lon, final int level) {
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78 | long x = lon2x(lon);
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79 | long y = lat2y(lat);
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80 | int shift = NR_LEVELS-level-1;
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81 | return (byte) ((x >> shift & 1) * 2 + (y >> shift & 1));
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82 | }
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83 | }
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