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DOC: Update fiona CRS compatibility for fiona 1.9+ #1609

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snowman2 merged 1 commit into from
Jul 25, 2026
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DOC: Update fiona CRS compatibility for fiona 1.9+ #1609

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36 changes: 24 additions & 12 deletions docs/crs_compatibility.rst
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Expand Up @@ -112,17 +112,19 @@ fiona

https://github.com/Toblerity/Fiona

Converting from `fiona` CRS to `pyproj.crs.CRS`
Converting from `fiona.crs.CRS` to `pyproj.crs.CRS`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Fiona currently stores the CRS as a PROJ string dictionary in the `crs`
attribute. As such, it is best to use the `crs_wkt` attribute.
If you have `fiona >= 1.9`, the CRS of a dataset is a `fiona.crs.CRS`
that you can pass in directly::

It is also useful to know that plans exist to add CRS class.
Related GitHub issue `here <https://github.com/Toblerity/Fiona/issues/714>`__.
import fiona
from pyproj.crs import CRS

with fiona.open(...) as fds:
proj_crs = CRS.from_user_input(fds.crs)

Example::
Otherwise, you should use the `crs_wkt` attribute::

import fiona
from pyproj.crs import CRS
Expand All @@ -131,27 +133,37 @@ Example::
proj_crs = CRS.from_wkt(fds.crs_wkt)


Converting from `pyproj.crs.CRS` for `fiona`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Converting from `pyproj.crs.CRS` to `fiona.crs.CRS`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. warning:: WKT2 is only supported in GDAL 3+

If you have `fiona >= 1.9` and GDAL 3+, then you can pass in the `pyproj.crs.CRS`
directly::

import fiona.crs
from pyproj.crs import CRS

proj_crs = CRS.from_epsg(4326)
fio_crs = fiona.crs.CRS.from_user_input(proj_crs)

If you want to be compatible across GDAL versions, you can do::

from packaging import version

import fiona
import fiona.crs
from pyproj.crs import CRS
from pyproj.enums import WktVersion

proj_crs = CRS.from_epsg(4326)

if version.parse(fiona.__gdal_version__) < version.parse("3.0.0"):
fio_crs = proj_crs.to_wkt(WktVersion.WKT1_GDAL)
fio_crs = fiona.crs.CRS.from_wkt(proj_crs.to_wkt(WktVersion.WKT1_GDAL))
else:
# GDAL 3+ can use WKT2
fio_crs = dc_crs.to_wkt()
fio_crs = fiona.crs.CRS.from_wkt(proj_crs.to_wkt())

# with fiona.open(..., "w", crs_wkt=fio_crs) as fds:
# with fiona.open(..., "w", crs=fio_crs) as fds:
# ...


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1 change: 1 addition & 0 deletions docs/history.rst
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Expand Up @@ -13,6 +13,7 @@ Latest
- ENH: Added grid_check kwarg to :class:`pyproj.transformer.TransformerGroup` mirroring PROJ CLI ``--grid-check``
- ENH: Added :class:`pyproj.enums.GridAvailabilityUse` enum for TransformerGroup ``grid_check`` kwarg
- ENH: Added always_xy kwarg to :meth:`pyproj.transformer.Transformer.from_pipeline`
- DOC: Update fiona CRS compatibility for fiona 1.9+ (issue #1360)
- BUG: Clear CONTEXT_THREAD_KEY when destroying PJ_CONTEXT (pull #1541)
- BUG: Default skew angle for CF grid mapping oblique mercator to 90 (issue #1506)
- BLD: update build-time dependencies
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