Prime meridian equivalence: increase tolerance

3 files changed, 13 insertions, 4 deletions

diff --git a/include/proj/common.hpp b/include/proj/common.hpp
index 91756c62..29d2c774 100644
--- a/include/proj/common.hpp
+++ b/include/proj/common.hpp
@@ -158,10 +158,14 @@ class Measure : public util::BaseObject {
 
     PROJ_DLL bool operator==(const Measure &other) PROJ_CONST_DECL;
 
+    /** Default maximum resulative error. */
+    static constexpr double DEFAULT_MAX_REL_ERROR = 1e-10;
+
     PROJ_INTERNAL bool
     _isEquivalentTo(const Measure &other,
                     util::IComparable::Criterion criterion =
-                        util::IComparable::Criterion::STRICT) const;
+                        util::IComparable::Criterion::STRICT,
+                    double maxRelativeError = DEFAULT_MAX_REL_ERROR) const;
 
   private:
     PROJ_OPAQUE_PRIVATE_DATA
diff --git a/src/common.cpp b/src/common.cpp
index 2a9d17c7..bd690924 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -370,15 +370,17 @@ bool Measure::operator==(const Measure &other) PROJ_CONST_DEFN {
 /** \brief Returns whether an object is equivalent to another one.
  * @param other other object to compare to
  * @param criterion comparaison criterion.
+ * @param maxRelativeError Maximum relative error allowed.
  * @return true if objects are equivalent.
  */
 bool Measure::_isEquivalentTo(const Measure &other,
-                              util::IComparable::Criterion criterion) const {
+                              util::IComparable::Criterion criterion,
+                              double maxRelativeError) const {
     if (criterion == util::IComparable::Criterion::STRICT) {
         return operator==(other);
     }
     return std::fabs(getSIValue() - other.getSIValue()) <=
-           1e-10 * std::fabs(getSIValue());
+           maxRelativeError * std::fabs(getSIValue());
 }
 
 // ---------------------------------------------------------------------------
diff --git a/src/datum.cpp b/src/datum.cpp
index 9f9fb4ec..975a870a 100644
--- a/src/datum.cpp
+++ b/src/datum.cpp
@@ -388,7 +388,10 @@ bool PrimeMeridian::_isEquivalentTo(
         !IdentifiedObject::_isEquivalentTo(other, criterion)) {
         return false;
     }
-    return longitude()._isEquivalentTo(otherPM->longitude(), criterion);
+    // In MapInfo, the Paris prime meridian is returned as 2.3372291666667
+    // instead of the official value of 2.33722917, which is a relative
+    // error in the 1e-9 range.
+    return longitude()._isEquivalentTo(otherPM->longitude(), criterion, 1e-8);
 }
 //! @endcond