gdalwarp: add a heuristic to clamp northings when projecting from geo…

…graphic to Mercator (typically EPSG:3857) (fixes #8730)
OSGeo · Nov 21, 2023 · bf16533 · bf16533
1 parent 615595c
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diff --git a/apps/gdalwarp_lib.cpp b/apps/gdalwarp_lib.cpp
@@ -3426,6 +3426,75 @@ static GDALDatasetH GDALWarpCreateOutput(
     if (EQUAL(pszFormat, "VRT"))
         bVRT = true;
 
+    // Special case for geographic to Mercator (typically EPSG:4326 to EPSG:3857)
+    // where latitudes close to 90 go to infinity
+    // We clamp latitudes between ~ -85 and ~ 85 degrees.
+    const char *pszDstSRS = CSLFetchNameValue(papszTO, "DST_SRS");
+    if (nSrcCount == 1 && pszDstSRS && psOptions->dfMinX == 0.0 &&
+        psOptions->dfMinY == 0.0 && psOptions->dfMaxX == 0.0 &&
+        psOptions->dfMaxY == 0.0)
+    {
+        auto hSrcDS = pahSrcDS[0];
+        const auto osSrcSRS = GetSrcDSProjection(pahSrcDS[0], papszTO);
+        OGRSpatialReference oSrcSRS;
+        oSrcSRS.SetAxisMappingStrategy(OAMS_TRADITIONAL_GIS_ORDER);
+        oSrcSRS.SetFromUserInput(osSrcSRS.c_str());
+        OGRSpatialReference oDstSRS;
+        oDstSRS.SetAxisMappingStrategy(OAMS_TRADITIONAL_GIS_ORDER);
+        oDstSRS.SetFromUserInput(pszDstSRS);
+        const char *pszProjection = oDstSRS.GetAttrValue("PROJECTION");
+        const char *pszMethod = CSLFetchNameValue(papszTO, "METHOD");
+        double adfSrcGT[6];
+        // This MAX_LAT values is equivalent to the semi_major_axis * PI
+        // easting/northing value only for EPSG:3857, but it is also quite
+        // reasonable for other Mercator projections
+        constexpr double MAX_LAT = 85.0511287798066;
+        constexpr double EPS = 1e-3;
+        const auto GetMinLon = [&adfSrcGT]() { return adfSrcGT[0]; };
+        const auto GetMaxLon = [&adfSrcGT, hSrcDS]()
+        { return adfSrcGT[0] + adfSrcGT[1] * GDALGetRasterXSize(hSrcDS); };
+        const auto GetMinLat = [&adfSrcGT, hSrcDS]()
+        { return adfSrcGT[3] + adfSrcGT[5] * GDALGetRasterYSize(hSrcDS); };
+        const auto GetMaxLat = [&adfSrcGT]() { return adfSrcGT[3]; };
+        if (oSrcSRS.IsGeographic() && !oSrcSRS.IsDerivedGeographic() &&
+            pszProjection && EQUAL(pszProjection, SRS_PT_MERCATOR_1SP) &&
+            oDstSRS.GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0) == 0 &&
+            (pszMethod == nullptr || EQUAL(pszMethod, "GEOTRANSFORM")) &&
+            CSLFetchNameValue(papszTO, "COORDINATE_OPERATION") == nullptr &&
+            CSLFetchNameValue(papszTO, "SRC_METHOD") == nullptr &&
+            CSLFetchNameValue(papszTO, "DST_METHOD") == nullptr &&
+            GDALGetGeoTransform(hSrcDS, adfSrcGT) == CE_None &&
+            adfSrcGT[2] == 0 && adfSrcGT[4] == 0 && adfSrcGT[5] < 0 &&
+            GetMinLon() >= -180 - EPS && GetMaxLon() <= 180 + EPS &&
+            ((GetMaxLat() > MAX_LAT && GetMinLat() < MAX_LAT) ||
+             (GetMaxLat() > -MAX_LAT && GetMinLat() < -MAX_LAT)) &&
+            GDALGetMetadata(hSrcDS, "GEOLOC_ARRAY") == nullptr &&
+            GDALGetMetadata(hSrcDS, "RPC") == nullptr)
+        {
+            auto poCT = std::unique_ptr<OGRCoordinateTransformation>(
+                OGRCreateCoordinateTransformation(&oSrcSRS, &oDstSRS));
+            if (poCT)
+            {
+                double xLL = std::max(GetMinLon(), -180.0);
+                double yLL = std::max(GetMinLat(), -MAX_LAT);
+                double xUR = std::min(GetMaxLon(), 180.0);
+                double yUR = std::min(GetMaxLat(), MAX_LAT);
+                if (poCT->Transform(1, &xLL, &yLL) &&
+                    poCT->Transform(1, &xUR, &yUR))
+                {
+                    psOptions->dfMinX = xLL;
+                    psOptions->dfMinY = yLL;
+                    psOptions->dfMaxX = xUR;
+                    psOptions->dfMaxY = yUR;
+                    CPLError(CE_Warning, CPLE_AppDefined,
+                             "Clamping output bounds to (%f,%f) -> (%f, %f)",
+                             psOptions->dfMinX, psOptions->dfMinY,
+                             psOptions->dfMaxX, psOptions->dfMaxY);
+                }
+            }
+        }
+    }
+
     /* If (-ts and -te) or (-tr and -te) are specified, we don't need to compute
      * the suggested output extent */
     const bool bNeedsSuggestedWarpOutput =

diff --git a/autotest/utilities/test_gdalwarp_lib.py b/autotest/utilities/test_gdalwarp_lib.py
@@ -2655,6 +2655,41 @@ def test_gdalwarp_lib_bug_4326_to_3857():
     assert cs == 4672
 
 
+###############################################################################
+# Test warping full world from EPSG:4326 to EPSG:3857
+
+
+def test_gdalwarp_lib_full_world_4326_to_3857():
+    class MyHandler:
+        def __init__(self):
+            self.warning_raised = False
+
+        def callback(self, err_type, err_no, err_msg):
+            if err_type == gdal.CE_Warning and "Clamping output bounds to" in err_msg:
+                self.warning_raised = True
+
+    my_error_handler = MyHandler()
+    with gdaltest.error_handler(my_error_handler.callback):
+        ds = gdal.Warp(
+            "",
+            "../gdrivers/data/small_world.tif",
+            options="-f MEM -t_srs EPSG:3857",
+        )
+    assert my_error_handler.warning_raised
+    assert ds.GetGeoTransform() == pytest.approx(
+        (
+            -20037508.342789244,
+            103286.12547829507,
+            0.0,
+            20037508.342789248,
+            0.0,
+            -103286.12547829509,
+        )
+    )
+    assert ds.RasterXSize == 388
+    assert ds.RasterYSize == 388
+
+
 ###############################################################################
 # Test warping of single source to COG