Setting coordinate reference system

Note

The code can be downloaded from https://github.com/GISMentors/yungo-plugins/tree/master/src/fiberplanitconvert-04-qgis-shp-proj

When loading a new layer into project the coordinate reference system of the layer must be defined. Otherwise a dialog for picking the correct coordinate reference system appears.

To fix this, we will set the coordinate reference system of the new created layer according to the input data file.

We are creating two layers:

  1. First layer is the memory layer, which is just used for simplicity of the manipulation with new features
  2. Second layer is a target output Shapefile

Both of them are created slightly in different way, but the both can have information about coordinate reference system assigned.

Memory layer

The memory layer is partly created by the URI QgsDatasSourceUri. We just need to add:

crs=epsg:NUMBER

To the URI

Shapefile

Shapefile is created using QgsVectorFileWriter.writeAsVectorFormat() function, which can have QgsCoordinateReferenceSystem type as the 4th parameter.

Coordinate reference system of the input data can be obtained by layer.crs()

EPSG code can be obtained by using crs.authid().

>>> crs = QgsCoordinateReferenceSystem.fromEpsgId(4326)
>>> crs.authid()
EPSG:4326
>>> crs.toWkt()
'GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY
["EPSG","9122"]],AUTHORITY["EPSG","4326"]]'

Úkol

Set coordinate reference system for memory layer as well as for a new Shapefile.