In [1]:

import gdal
import osr

gdal.UseExceptions()
gdal.VersionInfo()

Out[1]:

'2040100'

Define projections¶

In [2]:

srs_4326 = osr.SpatialReference()
srs_4326.ImportFromEPSG(4326)

Out[2]:

In [3]:

srs_3857 = osr.SpatialReference()
srs_3857.ImportFromEPSG(3857)

Out[3]:

Define transformations¶

In [4]:

ct_3857_to_4326 = osr.CoordinateTransformation(srs_3857, srs_4326)
ct_4326_to_3857 = osr.CoordinateTransformation(srs_4326, srs_3857)

Forward transform (x, y)¶

In [5]:

lat = 50.0
lon = -120.0

# this output is equivalent to the cmd (gdaltransform.exe)
mapx, mapy, z = ct_4326_to_3857.TransformPoint(lon, lat)
mapx, mapy

Out[5]:

(-13358338.89519283, 6446275.8410171615)

Forward transform (y, x)¶

In [6]:

lat = 50.0
lon = -120.0

# Incorrect output, as expected (wrong order of arguments)
mapy, mapx, z = ct_4326_to_3857.TransformPoint(lat, lon)
mapy, mapx

Out[6]:

(0.872664625997165, -2.0943951023931957)

Backward transform (x, y)¶

In [7]:

mapx = -13358338.895192828
mapy = 6446275.841017158

# this output is equivalent to the cmd (gdaltransform.exe)
ct_3857_to_4326.TransformPoint(mapx, mapy)

Out[7]:

(-119.99999999999996, 49.99999999999998, 0.0)

Backward transform (y, x)¶

In [8]:

mapx = -13358338.895192828
mapy = 6446275.841017158

# Incorrect output, as expected (wrong order of arguments)
ct_3857_to_4326.TransformPoint(mapy, mapx)

Out[8]:

(57.90788113636133, -75.95934455387824, 0.0)

CMD output reference¶

In [9]:

# (py37) C:\Users\Rutger>gdaltransform --version
# GDAL 2.4.1, released 2019/03/15

# (py37) C:\Users\Rutger>gdaltransform -s_srs EPSG:4326 -t_srs EPSG:3857
# -120 50
# -13358338.8951928 6446275.84101716 0

CoordinateTransform docstring¶

In [10]:

# docstring suggests (x,y,z)
ct_4326_to_3857.TransformPoint?

Signature: ct_4326_to_3857.TransformPoint(*args)
Docstring:
TransformPoint(CoordinateTransformation self, double [3] inout)
TransformPoint(CoordinateTransformation self, double x, double y, double z=0.0)
File:      c:\miniconda3\envs\py37\lib\site-packages\osgeo\osr.py
Type:      method

In [ ]: