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Projection API

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Selection Algorithm

We use the EPSG Geodetic Parameter Dataset for selecting a PCS.

Choosing a relevant PCS for a given operation must take into consideration the needs of the application.

The selection algorithm prioritizes the following:

  1. The units along both axes must match the given units (either feet or meters)
  2. The area of the PCS must wholly contain the shape
  3. Given the above, the PCS with the smallest area is chosen

PCS with smaller areas likely have lower distortion.

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Choosing a PCS

Using the mundipy.pcs library, we can choose a reasonable PCS, given any shapely geometry with WGS84 coordinates (ordered: longitude, latitude).

choose_pcs.py
from mundipy.pcs import choose_pcs
from shapely.geometry import Point

choose_pcs(Point(-118.24, 34.052), units='feet')
# {
#     'name': 'NAD27 / California zone VII',
#     'epsg': 26799,
#     'crs': 'EPSG:26799',
#     'units': 'feet'
# }

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Suggest multiple PCS’s

We can also suggest multiple projections with suggest_pcs:

suggest_pcs.py
from mundipy.pcs import suggest_pcs
from shapely.geometry import Point

suggest_pcs(Point(3.36, 52.54), units='meters', n=2)
# [{
#     "name": "ED50 / TM 5 NE",
#     "epsg": 23095,
#     "crs": "EPSG:23095",
#     "units": "meters"
# },
# {
#     "name": "ED50 / UTM zone 31N",
#     "epsg": 23031,
#     "crs": "EPSG:23031",
#     "units": "meters"
# }]

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Creating a pyproj.CRS

To manage your coordinate reference system manually, we recommend using pyproj.

pyproj.CRS('EPSG:23095')