createFromWkt(): be tolerant to missing scale_factor parameter (fixes #1700)

This is invalid WKT, but GDAL 2.4 used to accept it and make a reasonable
use of it...

Currently we default it to 0 which is non sensical. Better use 1 as GDAL 2.4
did, and emit a warning.

Other fix: proj_create_from_wkt() was documented to operate by default in
non-strict validation mode, but it was actually in strict mode. So do as
documented.

1 files changed, 20 insertions, 13 deletions

diff --git a/src/iso19111/coordinateoperation.cpp b/src/iso19111/coordinateoperation.cpp
index c7581642..5ac81aa1 100644
--- a/src/iso19111/coordinateoperation.cpp
+++ b/src/iso19111/coordinateoperation.cpp
@@ -6056,24 +6056,31 @@ void Conversion::_exportToPROJString(
                 if (!param->proj_name) {
                     continue;
                 }
-                auto value =
+                const auto value =
                     parameterValueMeasure(param->wkt2_name, param->epsg_code);
+                double valueConverted = 0;
+                if (value == nullMeasure) {
+                    // Deal with missing values. In an ideal world, this would
+                    // not happen
+                    if (param->epsg_code ==
+                        EPSG_CODE_PARAMETER_SCALE_FACTOR_AT_NATURAL_ORIGIN) {
+                        valueConverted = 1.0;
+                    }
+                } else if (param->unit_type ==
+                           common::UnitOfMeasure::Type::ANGULAR) {
+                    valueConverted =
+                        value.convertToUnit(common::UnitOfMeasure::DEGREE);
+                } else {
+                    valueConverted = value.getSIValue();
+                }
+
                 if (mapping->epsg_code ==
                         EPSG_CODE_METHOD_LAMBERT_CONIC_CONFORMAL_1SP &&
                     strcmp(param->proj_name, "lat_1") == 0) {
-                    formatter->addParam(
-                        param->proj_name,
-                        value.convertToUnit(common::UnitOfMeasure::DEGREE));
-                    formatter->addParam(
-                        "lat_0",
-                        value.convertToUnit(common::UnitOfMeasure::DEGREE));
-                } else if (param->unit_type ==
-                           common::UnitOfMeasure::Type::ANGULAR) {
-                    formatter->addParam(
-                        param->proj_name,
-                        value.convertToUnit(common::UnitOfMeasure::DEGREE));
+                    formatter->addParam(param->proj_name, valueConverted);
+                    formatter->addParam("lat_0", valueConverted);
                 } else {
-                    formatter->addParam(param->proj_name, value.getSIValue());
+                    formatter->addParam(param->proj_name, valueConverted);
                 }
             }