BaseSpatialField.geodetic should return SpatialReference.geographic

[Sergey Fedoseev]

At this moment BaseSpatialField.geodetic checks if the unit name associated with the field is in the list of geodetic_units = ('decimal degree', 'degree'), but it could simply return SpatialReference.geographic because units are geodetic iif SRS is geographic.

The current implementation of BaseSpatialField.geodetic gives incorrect result for some SRSes:

In [1]: from django.db import connection
In [2]: from django.contrib.gis.db.models.fields import BaseSpatialField

In [5]: BaseSpatialField(srid=4901).geodetic(connection)
Out[5]: False

In [10]: from django.contrib.gis.gdal import SpatialReference
In [11]: print(SpatialReference(4901))
GEOGCS["ATF (Paris)",
    DATUM["Ancienne_Triangulation_Francaise_Paris",
        SPHEROID["Plessis 1817",6376523,308.64,
            AUTHORITY["EPSG","7027"]],
        AUTHORITY["EPSG","6901"]],
    PRIMEM["Paris RGS",2.337208333333333,
        AUTHORITY["EPSG","8914"]],
    UNIT["grad",0.01570796326794897,
        AUTHORITY["EPSG","9105"]],
    AUTHORITY["EPSG","4901"]]

In [12]: SpatialReference(4901).geographic
Out[12]: True

[Sergey Fedoseev]

​PR

[Tim Graham <timograham@…>]

In df8f1d01:

Fixed #27972 -- Made BaseSpatialField.geodetic() use SpatialReference.geographic.