Gotchas/FAQ

This is a page for some suggestions, gotchas, and FAQs.

Also see:

• Getting Started

• PROJ FAQ

+init=<auth>:<auth_code> should be replaced with <auth>:<auth_code>

The +init=<auth>:<auth_code> syntax is deprecated and will be removed in future versions of PROJ. Also, if you use the +init syntax, you may have problems initializing projections when the other syntax works.

>>> from pyproj import CRS
>>> CRS("ESRI:54009")
<Projected CRS: ESRI:54009>
Name: World_Mollweide
Axis Info [cartesian]:
- E[east]: Easting (metre)
- N[north]: Northing (metre)
Area of Use:
- name: World
- bounds: (-180.0, -90.0, 180.0, 90.0)
Coordinate Operation:
- name: World_Mollweide
- method: Mollweide
Datum: World Geodetic System 1984
- Ellipsoid: WGS 84
- Prime Meridian: Greenwich

>>> CRS("+init=ESRI:54009")
...
pyproj.exceptions.CRSError: Invalid projection: +init=ESRI:54009 +type=crs: (Internal Proj Error: proj_create: cannot expand +init=ESRI:54009 +type=crs)

Proj (Not a generic latitude/longitude to projection converter)

Proj is limited to converting between geographic and projection coordinates within one datum. If you have coordinates in latitude and longitude, and you want to convert it to your projection, it is recommended to use the Transformer as it takes into account datum shifts.

You likely want to start from EPSG:4326 (WGS84) for coordinates as latitude and longitude.

>>> from pyproj import CRS
>>> crs_4326 = CRS("WGS84")
>>> crs_4326
<Geographic 2D CRS: EPSG:4326>
Name: WGS 84
Axis Info [ellipsoidal]:
- Lat[north]: Geodetic latitude (degree)
- Lon[east]: Geodetic longitude (degree)
Area of Use:
- name: World
- bounds: (-180.0, -90.0, 180.0, 90.0)
Datum: World Geodetic System 1984
- Ellipsoid: WGS 84
- Prime Meridian: Greenwich

Then, use the Transformer to transform from latitude and longitude to your projection as you might have a projection with a different datum.

>>> crs_proj = CRS("EPSG:28992")
>>> crs_proj
<Projected CRS: EPSG:28992>
Name: Amersfoort / RD New
Axis Info [cartesian]:
- X[east]: Easting (metre)
- Y[north]: Northing (metre)
Area of Use:
- name: Netherlands - onshore
- bounds: (3.2, 50.75, 7.22, 53.7)
Coordinate Operation:
- name: RD New
- method: Oblique Stereographic
Datum: Amersfoort
- Ellipsoid: Bessel 1841
- Prime Meridian: Greenwich
>>> crs_proj.datum == crs_4326.datum
False
>>> from pyproj import Transformer
>>> transformer = Transformer.from_crs(crs_4326, crs_proj)
>>> transformer.transform(52.067567, 5.068913)
(133175.3690698233, 453300.86739169655)

If you use Proj, it will use the geodetic CRS with from the projected CRS with the same datum to do the transformation, which may not be what you want.

>>> from pyproj import Proj
>>> Proj('epsg:28992')(5.068913, 52.067567)
(133148.22970574044, 453192.24450392975)
>>> transg = Transformer.from_crs(crs_proj.geodetic_crs, crs_proj)
>>> transg.transform(52.067567, 5.068913)
(133148.22970574044, 453192.24450392975)

Upgrading to pyproj 2 from pyproj 1

We recommended using the Transformer and CRS in place of the Proj and transform().

Also see:

• Getting Started

• Optimize Transformations

pyproj 1 style:

>>> from functools import partial
>>> from pyproj import Proj, transform
>>> proj_4326 = Proj(init="epsg:4326")
>>> proj_3857 = Proj(init="epsg:3857")
>>> transformer = partial(transform, proj_4326, proj_3857)
>>> transformer(12, 12)

pyproj 2 style:

>>> from pyproj import Transformer
>>> transformer = Transformer.from_crs("epsg:4326", "epsg:3857")
>>> transformer.transform(12, 12)