Howto list EPSG codes as proj.4 strings from the new Proj 6 sqlite3 proj.db

Question

I want to list all EPSG codes from the new PROJ.6 tool in form of proj.4 strings. Is there a tool / SQL script to replicate the former /usr/share/proj/epsg file from the SQLite3 proj.db?

Answer 1

You can use Python for this purpose

Install the Python lib

# use version 2.4.2 as it install a version 6 of proj behind the scene
python3 -m pip install pyproj==2.4.2 pyproj

Then, run the following Python script

import os
import pyproj

all_epsg_crs_code = pyproj.get_codes('EPSG', 'CRS')

# Be aware that with to_proj4 usage you will get below warning
# UserWarning: You will likely lose important projection information when
# converting to a PROJ string from another format. See:
# https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems


with open('/tmp/epsg', 'w') as input_file:
    for i in all_epsg_crs_code:
        my_proj = pyproj.CRS("epsg:{}".format(i))
        old_epsg_string_format = """# {}{}<{}> {} <>""".format(
            my_proj.name,
            os.linesep,
            i,
            my_proj.to_proj4()
        )
        input_file.write(old_epsg_string_format)

You may want to set the path to your proj version content using https://pyproj4.github.io/pyproj/dev/installation.html#envvar-PROJ_DIR as by default Pyproj install it own binary/lib of proj.