Make tmerc an alias for etmerc. (#1234)

* Make tmerc an alias for etmerc

This switches the algorithm used in tmerc to the Poder/Engsager
tmerc algorithm. The original tmerc algorithm of Evenden/Snyder
origin can still be accessed by adding the +approx flag when
initializing a tmerc projection. The +approx flag can also
be used when initializing UTM projections, in which case the
Evenden/Snyder algorithm is used as well.

If a tmerc projection is instantiated on a spherical earth
the Evenden/Snyder algorithm is used as well since the
Poder/Engsager algorithm is only defined on the ellipsoid.

+proj=etmerc can still be instantiated for backwards compatibility
reasons.

Co-authored-by: Kristian Evers <kristianevers@gmail.com>
Co-authored-by: Even Rouault <even.rouault@spatialys.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/proj/io.hpp b/include/proj/io.hpp
index aedf0457..091efcb7 100644
--- a/include/proj/io.hpp
+++ b/include/proj/io.hpp
@@ -365,7 +365,7 @@ class PROJ_GCC_DLL PROJStringFormatter {
     PROJ_DLL ~PROJStringFormatter();
     //! @endcond
 
-    PROJ_DLL void setUseETMercForTMerc(bool flag);
+    PROJ_DLL void setUseApproxTMerc(bool flag);
 
     PROJ_DLL const std::string &toString() const;
 
@@ -378,7 +378,7 @@ class PROJ_GCC_DLL PROJStringFormatter {
     PROJ_DLL void startInversion();
     PROJ_DLL void stopInversion();
     PROJ_INTERNAL bool isInverted() const;
-    PROJ_INTERNAL bool getUseETMercForTMerc(bool &settingSetOut) const;
+    PROJ_INTERNAL bool getUseApproxTMerc() const;
     PROJ_INTERNAL void setCoordinateOperationOptimizations(bool enable);
 
     PROJ_DLL void