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Spherical mercator transformation should handle properly out of bounds latitudes #81145

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iverase merged 3 commits into from
Dec 1, 2021
Merged

Spherical mercator transformation should handle properly out of bounds latitudes #81145

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Spherical mercator transformation should handle properly out of bound…
iverase Nov 30, 2021
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iverase Nov 30, 2021
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iverase Nov 30, 2021
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4 changes: 3 additions & 1 deletion server/src/main/java/org/elasticsearch/common/geo/SphericalMercatorUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,8 @@ public class SphericalMercatorUtils {

public static final double MERCATOR_BOUNDS = 20037508.34;
private static final double MERCATOR_FACTOR = MERCATOR_BOUNDS / 180.0;
// latitude lower limit. Below this limit the transformation might result in -Infinity
private static final double LAT_LOWER_LIMIT = Math.nextUp(-90.0);

/**
* Transforms WGS84 longitude to a Spherical mercator longitude
Expand All @@ -29,7 +31,7 @@ public static double lonToSphericalMercator(double lon) {
* Transforms WGS84 latitude to a Spherical mercator latitude
*/
public static double latToSphericalMercator(double lat) {
double y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
double y = Math.log(Math.tan((90 + Math.max(lat, LAT_LOWER_LIMIT)) * Math.PI / 360)) / (Math.PI / 180);
return y * MERCATOR_FACTOR;
}

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27 changes: 22 additions & 5 deletions server/src/test/java/org/elasticsearch/common/geo/SphericalMercatorUtilTests.java
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Expand Up @@ -34,11 +34,28 @@ public void testLat() {
assertThat(latToSphericalMercator(GeoTileUtils.LATITUDE_MASK), Matchers.closeTo(MERCATOR_BOUNDS, 1e-7));
assertThat(latToSphericalMercator(-GeoTileUtils.LATITUDE_MASK), Matchers.closeTo(-MERCATOR_BOUNDS, 1e-7));
assertThat(latToSphericalMercator(0.0), Matchers.closeTo(0, 1e-7));
final double lat = latToSphericalMercator(
randomValueOtherThanMany(l -> l >= GeoTileUtils.LATITUDE_MASK || l <= -GeoTileUtils.LATITUDE_MASK, GeometryTestUtils::randomLat)
);
assertThat(lat, Matchers.greaterThanOrEqualTo(-MERCATOR_BOUNDS));
assertThat(lat, Matchers.lessThanOrEqualTo(MERCATOR_BOUNDS));
{
final double lat = latToSphericalMercator(
randomValueOtherThanMany(
l -> l >= GeoTileUtils.LATITUDE_MASK || l <= -GeoTileUtils.LATITUDE_MASK,
GeometryTestUtils::randomLat
)
);
assertThat(lat, Matchers.greaterThanOrEqualTo(-MERCATOR_BOUNDS));
assertThat(lat, Matchers.lessThanOrEqualTo(MERCATOR_BOUNDS));
}
{
// out of bounds values
final double lat = latToSphericalMercator(randomDoubleBetween(GeoTileUtils.LATITUDE_MASK, 90, false));
assertThat(lat, Matchers.greaterThan(MERCATOR_BOUNDS));
assertTrue(Double.isFinite(latToSphericalMercator(90)));
}
{
// out of bounds values
final double lat = latToSphericalMercator(-randomDoubleBetween(GeoTileUtils.LATITUDE_MASK, 90, false));
assertThat(lat, Matchers.lessThan(-MERCATOR_BOUNDS));
assertTrue(Double.isFinite(latToSphericalMercator(-90)));
}
}

public void testRectangle() {
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