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projection.rst

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Projection

Create Projection

from osgeo import osr
spatialRef = osr.SpatialReference()
spatialRef.ImportFromEPSG(2927)         # from EPSG

Reproject a Geometry

from osgeo import ogr
from osgeo import osr

source = osr.SpatialReference()
source.ImportFromEPSG(2927)

target = osr.SpatialReference()
target.ImportFromEPSG(4326)

transform = osr.CoordinateTransformation(source, target)

point = ogr.CreateGeometryFromWkt("POINT (1120351.57 741921.42)")
point.Transform(transform)

print point.ExportToWkt()

Get Projection

from osgeo import ogr, osr
driver = ogr.GetDriverByName('ESRI Shapefile')
dataset = driver.Open(r'c:\data\yourshpfile.shp')

# from Layer
layer = dataset.GetLayer()
spatialRef = layer.GetSpatialRef()
# from Geometry
feature = layer.GetNextFeature()
geom = feature.GetGeometryRef()
spatialRef = geom.GetSpatialReference()

Reproject a Layer

from osgeo import ogr, osr
import os

driver = ogr.GetDriverByName('ESRI Shapefile')

# input SpatialReference
inSpatialRef = osr.SpatialReference()
inSpatialRef.ImportFromEPSG(2927)

# output SpatialReference
outSpatialRef = osr.SpatialReference()
outSpatialRef.ImportFromEPSG(4326)

# create the CoordinateTransformation
coordTrans = osr.CoordinateTransformation(inSpatialRef, outSpatialRef)

# get the input layer
inDataSet = driver.Open(r'c:\data\spatial\basemap.shp')
inLayer = inDataSet.GetLayer()

# create the output layer
outputShapefile = r'c:\data\spatial\basemap_4326.shp'
if os.path.exists(outputShapefile):
    driver.DeleteDataSource(outputShapefile)
outDataSet = driver.CreateDataSource(outputShapefile)
outLayer = outDataSet.CreateLayer("basemap_4326", geom_type=ogr.wkbMultiPolygon)

# add fields
inLayerDefn = inLayer.GetLayerDefn()
for i in range(0, inLayerDefn.GetFieldCount()):
    fieldDefn = inLayerDefn.GetFieldDefn(i)
    outLayer.CreateField(fieldDefn)

# get the output layer's feature definition
outLayerDefn = outLayer.GetLayerDefn()

# loop through the input features
inFeature = inLayer.GetNextFeature()
while inFeature:
    # get the input geometry
    geom = inFeature.GetGeometryRef()
    # reproject the geometry
    geom.Transform(coordTrans)
    # create a new feature
    outFeature = ogr.Feature(outLayerDefn)
    # set the geometry and attribute
    outFeature.SetGeometry(geom)
    for i in range(0, outLayerDefn.GetFieldCount()):
        outFeature.SetField(outLayerDefn.GetFieldDefn(i).GetNameRef(), inFeature.GetField(i))
    # add the feature to the shapefile
    outLayer.CreateFeature(outFeature)
    # dereference the features and get the next input feature
    outFeature = None
    inFeature = inLayer.GetNextFeature()

# Save and close the shapefiles
inDataSet = None
outDataSet = None

Export Projection

from osgeo import ogr, osr
driver = ogr.GetDriverByName('ESRI Shapefile')
dataset = driver.Open(r'c:\data\yourshpfile.shp')
layer = dataset.GetLayer()
spatialRef = layer.GetSpatialRef()

spatialRef.ExportToWkt()
spatialRef.ExportToPrettyWkt()
spatialRef.ExportToPCI()
spatialRef.ExportToUSGS()
spatialRef.ExportToXML()

Create an ESRI.prj file

from osgeo import ogr, osr

spatialRef = osr.SpatialReference()
spatialRef.ImportFromEPSG(26912)

spatialRef.MorphToESRI()
file = open('yourshpfile.prj', 'w')
file.write(spatialRef.ExportToWkt())
file.close()