Hi everyone,

```
I'm Dave, and I'm a developer from the U.K.
I have implemented Proj4 in C++ into our software but I'm getting transformation errors compared to
https://epsg.io/transform#s_srs=23037&t_srs=32637&x=564928.5884000&y=4262281.7699000
whether we use the database or well known text.
We're using WKT2 2019 but if I convert to WKT1 and compare my WKT to ESPG (see below) I notice that
I'm not including the TOWGS84 clause.
If I manually add the clause to my WKT, I get the required transformation.
Does anyone have any suggestions as to why there is a discrepancy with my WKT compared to ESPG? I'm very new to all this, so would really appreciate some far more expert advise.
Thank you in advance
Dave
----------------------------------------------------------
My WKT2
----------------------------------------------------------
PROJCRS["ED50 / UTM zone 37N",
BASEGEOGCRS["ED50",
DATUM["European Datum 1950",
ELLIPSOID["International 1924",6378388,297,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4230]],
CONVERSION["UTM zone 37N",
METHOD["Transverse Mercator",
ID["EPSG",9807]],
PARAMETER["Latitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",39,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["Scale factor at natural origin",0.9996,
SCALEUNIT["unity",1],
ID["EPSG",8805]],
PARAMETER["False easting",500000,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",0,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["(E)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["(N)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["unknown"],
AREA["Europe - 36°E to 42°E and ED50 by country"],
BBOX[29.18,36,79.09,42]],
ID["EPSG",23037]]
----------------------------------------------------------
PROJCRS["WGS 84 / UTM zone 37N",
BASEGEOGCRS["WGS 84",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4326]],
CONVERSION["UTM zone 37N",
METHOD["Transverse Mercator",
ID["EPSG",9807]],
PARAMETER["Latitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",39,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["Scale factor at natural origin",0.9996,
SCALEUNIT["unity",1],
ID["EPSG",8805]],
PARAMETER["False easting",500000,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",0,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["(E)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["(N)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["unknown"],
AREA["World - N hemisphere - 36°E to 42°E - by country"],
BBOX[0,36,84,42]],
ID["EPSG",32637]]
----------------------------------------------------------
My WKT1
----------------------------------------------------------
PROJCS["ED50 / UTM zone 37N",
GEOGCS["ED50",
DATUM["European_Datum_1950",
SPHEROID["International 1924",6378388,297,
AUTHORITY["EPSG","7022"]],
AUTHORITY["EPSG","6230"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4230"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",39],
PARAMETER["scale_factor",0.9996],
PARAMETER["false_easting",500000],
PARAMETER["false_northing",0],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AXIS["Easting",EAST],
AXIS["Northing",NORTH],
AUTHORITY["EPSG","23037"]]
----------------------------------------------------------
WKT1 from https://epsg.io/23037
----------------------------------------------------------
PROJCS["ED50 / UTM zone 37N",
GEOGCS["ED50",
DATUM["European_Datum_1950",
SPHEROID["International 1924",6378388,297,
AUTHORITY["EPSG","7022"]],
TOWGS84[-87,-98,-121,0,0,0,0],
AUTHORITY["EPSG","6230"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4230"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",39],
PARAMETER["scale_factor",0.9996],
PARAMETER["false_easting",500000],
PARAMETER["false_northing",0],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
AXIS["Easting",EAST],
AXIS["Northing",NORTH],
AUTHORITY["EPSG","23037"]]
```