Bug: Converting to "EPSG:3857" and its WKT2 definition give different values #545
Description
Summary:
- Converting from "EPSG:4326" to "EPSG:3857" gives a different result as converting from "EPSG:4326" to the WKT2 definition of 3857
- The former gives:
[ 111319.49079327357, 6766432.490645153 ] - The latter gives:
[ 111319.49079327357, 6800125.454397305 ] - This is different from pyproj in Python, where both versions give the second result
- This seems to imply a bug in the WKT2 parser (let me know if I should create this issue in https://github.com/proj4js/wkt-parser instead)
import proj4 from "proj4";
const WKT_3857 = `PROJCRS["WGS 84 / Pseudo-Mercator",
BASEGEOGCRS["WGS 84",
ENSEMBLE["World Geodetic System 1984 ensemble",
MEMBER["World Geodetic System 1984 (Transit)"],
MEMBER["World Geodetic System 1984 (G730)"],
MEMBER["World Geodetic System 1984 (G873)"],
MEMBER["World Geodetic System 1984 (G1150)"],
MEMBER["World Geodetic System 1984 (G1674)"],
MEMBER["World Geodetic System 1984 (G1762)"],
MEMBER["World Geodetic System 1984 (G2139)"],
MEMBER["World Geodetic System 1984 (G2296)"],
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]],
ENSEMBLEACCURACY[2.0]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4326]],
CONVERSION["Popular Visualisation Pseudo-Mercator",
METHOD["Popular Visualisation Pseudo Mercator",
ID["EPSG",1024]],
PARAMETER["Latitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["False easting",0,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",0,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["easting (X)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["northing (Y)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["Web mapping and visualisation."],
AREA["World between 85.06°S and 85.06°N."],
BBOX[-85.06,-180,85.06,180]],
ID["EPSG",3857]]
`;
const wktConverter = proj4("EPSG:4326", WKT_3857);
const source = [1, 52];
console.log(wktConverter.forward(source));
const epsgCodeConverter = proj4("EPSG:4326", "EPSG:3857");
console.log(epsgCodeConverter.forward(source));This prints:
[ 111319.49079327357, 6766432.490645153 ]
[ 111319.49079327357, 6800125.454397305 ]Python repro:
from pyproj import CRS, Transformer
epsg_4326 = CRS.from_epsg(4326)
epsg_3857 = CRS.from_epsg(3857)
epsg_3857_wkt = """PROJCRS["WGS 84 / Pseudo-Mercator",
BASEGEOGCRS["WGS 84",
ENSEMBLE["World Geodetic System 1984 ensemble",
MEMBER["World Geodetic System 1984 (Transit)"],
MEMBER["World Geodetic System 1984 (G730)"],
MEMBER["World Geodetic System 1984 (G873)"],
MEMBER["World Geodetic System 1984 (G1150)"],
MEMBER["World Geodetic System 1984 (G1674)"],
MEMBER["World Geodetic System 1984 (G1762)"],
MEMBER["World Geodetic System 1984 (G2139)"],
MEMBER["World Geodetic System 1984 (G2296)"],
ELLIPSOID["WGS 84",6378137,298.257223563,
LENGTHUNIT["metre",1]],
ENSEMBLEACCURACY[2.0]],
PRIMEM["Greenwich",0,
ANGLEUNIT["degree",0.0174532925199433]],
ID["EPSG",4326]],
CONVERSION["Popular Visualisation Pseudo-Mercator",
METHOD["Popular Visualisation Pseudo Mercator",
ID["EPSG",1024]],
PARAMETER["Latitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8801]],
PARAMETER["Longitude of natural origin",0,
ANGLEUNIT["degree",0.0174532925199433],
ID["EPSG",8802]],
PARAMETER["False easting",0,
LENGTHUNIT["metre",1],
ID["EPSG",8806]],
PARAMETER["False northing",0,
LENGTHUNIT["metre",1],
ID["EPSG",8807]]],
CS[Cartesian,2],
AXIS["easting (X)",east,
ORDER[1],
LENGTHUNIT["metre",1]],
AXIS["northing (Y)",north,
ORDER[2],
LENGTHUNIT["metre",1]],
USAGE[
SCOPE["Web mapping and visualisation."],
AREA["World between 85.06°S and 85.06°N."],
BBOX[-85.06,-180,85.06,180]],
ID["EPSG",3857]]
"""
transformer_epsg = Transformer.from_crs(epsg_4326, epsg_3857, always_xy=True)
transformer_wkt = Transformer.from_crs(epsg_4326, epsg_3857_wkt, always_xy=True)
coord = [1, 52]
print(transformer_epsg.transform(*coord))
# (111319.49079327357, 6800125.454397307)
print(transformer_wkt.transform(*coord))
# (111319.49079327357, 6800125.454397307)