importFromWKT v1: properly handle latitude_of_origin=0 for Mercator_1SP

2 files changed, 38 insertions, 8 deletions

diff --git a/src/io.cpp b/src/io.cpp
index 90732a32..3a980993 100644
--- a/src/io.cpp
+++ b/src/io.cpp
@@ -1199,8 +1199,8 @@ struct WKTParser::Private {
     static bool hasWebMercPROJ4String(const WKTNodeNNPtr &projCRSNode,
                                       const WKTNodeNNPtr &projectionNode);
 
-    static bool projectionHasParameter(const WKTNodeNNPtr &projCRSNode,
-                                       const char *paramName);
+    static std::string projectionGetParameter(const WKTNodeNNPtr &projCRSNode,
+                                              const char *paramName);
 
     ConversionNNPtr buildProjection(const WKTNodeNNPtr &projCRSNode,
                                     const WKTNodeNNPtr &projectionNode,
@@ -3044,19 +3044,20 @@ WKTParser::Private::buildProjection(const WKTNodeNNPtr &projCRSNode,
 
 // ---------------------------------------------------------------------------
 
-bool WKTParser::Private::projectionHasParameter(const WKTNodeNNPtr &projCRSNode,
-                                                const char *paramName) {
+std::string
+WKTParser::Private::projectionGetParameter(const WKTNodeNNPtr &projCRSNode,
+                                           const char *paramName) {
     for (const auto &childNode : projCRSNode->GP()->children()) {
         if (ci_equal(childNode->GP()->value(), WKTConstants::PARAMETER)) {
             const auto &childNodeChildren = childNode->GP()->children();
             if (childNodeChildren.size() == 2 &&
                 metadata::Identifier::isEquivalentName(
                     stripQuotes(childNodeChildren[0]).c_str(), paramName)) {
-                return true;
+                return childNodeChildren[1]->GP()->value();
             }
         }
     }
-    return false;
+    return std::string();
 }
 
 // ---------------------------------------------------------------------------
@@ -3078,10 +3079,12 @@ ConversionNNPtr WKTParser::Private::buildProjectionStandard(
     bool gdal_3026_hack = false;
     if (metadata::Identifier::isEquivalentName(wkt1ProjectionName.c_str(),
                                                "Mercator_1SP") &&
-        !projectionHasParameter(projCRSNode, "center_latitude")) {
+        projectionGetParameter(projCRSNode, "center_latitude").empty()) {
 
         // Hack for https://trac.osgeo.org/gdal/ticket/3026
-        if (projectionHasParameter(projCRSNode, "latitude_of_origin")) {
+        std::string lat0(
+            projectionGetParameter(projCRSNode, "latitude_of_origin"));
+        if (!lat0.empty() && lat0 != "0" && lat0 != "0.0") {
             wkt1ProjectionName = "Mercator_2SP";
             gdal_3026_hack = true;
         } else {
diff --git a/test/unit/test_io.cpp b/test/unit/test_io.cpp
index 7fdb1358..0cf36766 100644
--- a/test/unit/test_io.cpp
+++ b/test/unit/test_io.cpp
@@ -991,6 +991,33 @@ TEST(wkt_parse, wkt1_projected_with_PROJ4_extension) {
 
 // ---------------------------------------------------------------------------
 
+TEST(wkt_parse, wkt1_Mercator_1SP_with_latitude_origin_0) {
+    auto wkt = "PROJCS[\"unnamed\",\n"
+               "    GEOGCS[\"WGS 84\",\n"
+               "        DATUM[\"unknown\",\n"
+               "            SPHEROID[\"WGS84\",6378137,298.257223563]],\n"
+               "        PRIMEM[\"Greenwich\",0],\n"
+               "        UNIT[\"degree\",0.0174532925199433]],\n"
+               "    PROJECTION[\"Mercator_1SP\"],\n"
+               "    PARAMETER[\"latitude_of_origin\",0],\n"
+               "    PARAMETER[\"central_meridian\",0],\n"
+               "    PARAMETER[\"scale_factor\",1],\n"
+               "    PARAMETER[\"false_easting\",0],\n"
+               "    PARAMETER[\"false_northing\",0],\n"
+               "    UNIT[\"Meter\",1],\n"
+               "    AXIS[\"Easting\",EAST],\n"
+               "    AXIS[\"Northing\",NORTH]]";
+    auto obj = WKTParser().createFromWKT(wkt);
+
+    auto crs = nn_dynamic_pointer_cast<ProjectedCRS>(obj);
+    ASSERT_TRUE(crs != nullptr);
+    auto got_wkt = crs->exportToWKT(
+        WKTFormatter::create(WKTFormatter::Convention::WKT1_GDAL).get());
+    EXPECT_TRUE(got_wkt.find("Mercator_1SP") != std::string::npos) << got_wkt;
+}
+
+// ---------------------------------------------------------------------------
+
 TEST(wkt_parse, wkt1_krovak_south_west) {
     auto wkt =
         "PROJCS[\"S-JTSK / Krovak\","