vector_layers.rst

Vector Layers

Delete a file

from osgeo import ogr
import os

DriverName = "ESRI Shapefile"      # e.g.: GeoJSON, ESRI Shapefile
FileName = 'test.shp'
driver = ogr.GetDriverByName(DriverName)
if os.path.exists(FileName):
     driver.DeleteDataSource(FileName)

Is Ogr Installed

try:
  from osgeo import ogr
  print 'Import of ogr from osgeo worked.  Hurray!\n'
except:
  print 'Import of ogr from osgeo failed\n\n'

View Auto Generated Ogr Help

This code simply prints out the auto-generated help on the imported module. In this case it's OGR. This might not be the best way to scan the API's class methods. For a detailed description of the whole Python GDAL/OGR API, see the useful API docs.

import osgeo.ogr
print help(osgeo.ogr)

Get List of Ogr Drivers Alphabetically (A- Z)

It's always driven me a little nuts that the command line ogr2ogr --formats returns a 'random' list of drivers. This code returns the list of OGR drivers alphabetically from A - Z. .

import ogr
cnt = ogr.GetDriverCount()
formatsList = []  # Empty List

for i in range(cnt):
    driver = ogr.GetDriver(i)
    driverName = driver.GetName()
    if not driverName in formatsList:
        formatsList.append(driverName)

formatsList.sort() # Sorting the messy list of ogr drivers

for i in formatsList:
    print i

Is Ogr Driver Available by Driver Name

This code shows if a particular OGR driver is available. The exact names are the ones used on the OGR Vector Formats page in the "Code" column ([formats website]). This is the same names returned when you enter ogrinfo --formats on the command line.

Code Example Source: [website]

from osgeo import ogr

## Shapefile available?
driverName = "ESRI Shapefile"
drv = ogr.GetDriverByName( driverName )
if drv is None:
    print "%s driver not available.\n" % driverName
else:
    print  "%s driver IS available.\n" % driverName

## PostgreSQL available?
driverName = "PostgreSQL"
drv = ogr.GetDriverByName( driverName )
if drv is None:
    print "%s driver not available.\n" % driverName
else:
    print  "%s driver IS available.\n" % driverName

## Is File GeoDatabase available?
driverName = "FileGDB"
drv = ogr.GetDriverByName( driverName )
if drv is None:
    print "%s driver not available.\n" % driverName
else:
    print  "%s driver IS available.\n" % driverName

## SDE available?
driverName = "SDE"
drv = ogr.GetDriverByName( driverName )
if drv is None:
    print "%s driver not available.\n" % driverName
else:
    print  "%s driver IS available.\n" % driverName

Force Ogr Use Named Driver

Use only the specified driver to attempt to read the data file, taking into account special nature of the CSV driver which normally requires a .csv extension.

Source, Luke Pinner on GIS Stack Exchange: [website]

import sys
from osgeo import ogr

def main(in_file, in_format, out_file, out_format):
        if in_format == 'CSV' and in_file[-3:].lower() != 'csv':
                in_file = 'CSV:' + in_file
        in_ds = ogr.GetDriverByName(in_format).Open(in_file)
        out_ds  = ogr.GetDriverByName(out_format).CopyDataSource(in_ds, out_file)

if __name__ == '__main__':
        main(*sys.argv[1:])

Usage:

python ogr-convert.py [in file] [format driver] [out file/dir] {out format}

python ogr-convert.py x:incomingcoolstuff.txt CSV d:shapefiles

Get Shapefile Feature Count

This code example opens a shapefile and returns the number of features in it. Solution mined from: [web site]

import os
from osgeo import ogr

daShapefile = r"C:\Temp\Voting_Centers_and_Ballot_Sites.shp"

driver = ogr.GetDriverByName('ESRI Shapefile')

dataSource = driver.Open(daShapefile, 0) # 0 means read-only. 1 means writeable.

# Check to see if shapefile is found.
if dataSource is None:
    print 'Could not open %s' % (daShapefile)
else:
    print 'Opened %s' % (daShapefile)
    layer = dataSource.GetLayer()
    featureCount = layer.GetFeatureCount()
    print "Number of features in %s: %d" % (os.path.basename(daShapefile),featureCount)

Get All PostGIS layers in a PostgreSQL Database

This returns all the layers in a database of your choosing sorted in alphabetical order (of course). Just fill in the missing information and it should work.

from osgeo import ogr

databaseServer = "<IP of database server OR Name of database server"
databaseName = "<Name of database>"
databaseUser = "<User name>"
databasePW = "<User password>"


connString = "PG: host=%s dbname=%s user=%s password=%s" %(databaseServer,databaseName,databaseUser,databasePW)

conn = ogr.Open(connString)

layerList = []
for i in conn:
    daLayer = i.GetName()
    if not daLayer in layerList:
        layerList.append(daLayer)

layerList.sort()

for j in layerList:
    print j

# Close connection
conn = None

Get PostGIS Layer Feature Count By Layer Name

This code example opens a postgis connection and gets the specified layer name if it exists in the database. Otherwise it throws a nice error message

from osgeo import ogr
import sys

databaseServer = "<IP of database server OR Name of database server"
databaseName = "<Name of database>"
databaseUser = "<User name>"
databasePW = "<User password>"
connString = "PG: host=%s dbname=%s user=%s password=%s" % (databaseServer,databaseName,databaseUser,databasePW)

def GetPGLayer( lyr_name ):
    conn = ogr.Open(connString)

    lyr = conn.GetLayer( lyr_name )
    if lyr is None:
        print >> sys.stderr, '[ ERROR ]: layer name = "%s" could not be found in database "%s"' % ( lyr_name, databaseName )
        sys.exit( 1 )

    featureCount = lyr.GetFeatureCount()
    print "Number of features in %s: %d" % ( lyr_name , featureCount )

    # Close connection
    conn = None


if __name__ == '__main__':

    if len( sys.argv ) < 2:
        print >> sys.stderr, '[ ERROR ]: you must pass at least one argument -- the layer name argument'
        sys.exit( 1 )

    lyr_name = sys.argv[1]
    GetPGLayer( lyr_name )

Get all layers in an Esri File GeoDataBase

This returns all the layers in a Esri FileGDB in alphabetical order (of course). It needs GDAL/OGR 1.11.0 + but not any Esri dependency. That's the benefit of the OpenFileGDB driver developed by Ewen Rouault relative to the FileGDB driver.

# standard imports
import sys

# import OGR
from osgeo import ogr

# use OGR specific exceptions
ogr.UseExceptions()

# get the driver
driver = ogr.GetDriverByName("OpenFileGDB")

# opening the FileGDB
try:
    gdb = driver.Open(gdb_path, 0)
except Exception, e:
    print e
    sys.exit()

# list to store layers'names
featsClassList = []

# parsing layers by index
for featsClass_idx in range(gdb.GetLayerCount()):
    featsClass = gdb.GetLayerByIndex(featsClass_idx)
    featsClassList.append(featsClass.GetName())

# sorting
featsClassList.sort()

# printing
for featsClass in featsClassList:
    print featsClass

# clean close
del gdb

Load data to memory

This illustrates how to copy a dataset to memory with write access, providing fast data access.

from osgeo import ogr

#open an input datasource
indriver=ogr.GetDriverByName('SQLite')
srcdb = indriver.Open('OUTDATA.sqlite',0)

#create an output datasource in memory
outdriver=ogr.GetDriverByName('MEMORY')
source=outdriver.CreateDataSource('memData')

#open the memory datasource with write access
tmp=outdriver.Open('memData',1)

#copy a layer to memory
pipes_mem=source.CopyLayer(srcdb.GetLayer('pipes'),'pipes',['OVERWRITE=YES'])

#the new layer can be directly accessed via the handle pipes_mem or as source.GetLayer('pipes'):
layer=source.GetLayer('pipes')
for feature in layer:
    feature.SetField('SOMETHING',1)

Iterate over Features

from osgeo import ogr
import os

shapefile = "states.shp"
driver = ogr.GetDriverByName("ESRI Shapefile")
dataSource = driver.Open(shapefile, 0)
layer = dataSource.GetLayer()

for feature in layer:
    print feature.GetField("STATE_NAME")
layer.ResetReading()

You must call ResetReading if you want to start iterating over the layer again.

Get Geometry from each Feature in a Layer

from osgeo import ogr
import os

shapefile = "states.shp"
driver = ogr.GetDriverByName("ESRI Shapefile")
dataSource = driver.Open(shapefile, 0)
layer = dataSource.GetLayer()

for feature in layer:
    geom = feature.GetGeometryRef()
    print geom.Centroid().ExportToWkt()

Filter by attribute

from osgeo import ogr
import os

shapefile = "states.shp"
driver = ogr.GetDriverByName("ESRI Shapefile")
dataSource = driver.Open(shapefile, 0)
layer = dataSource.GetLayer()

layer.SetAttributeFilter("SUB_REGION = 'Pacific'")

for feature in layer:
    print feature.GetField("STATE_NAME")

Spatial Filter

from osgeo import ogr
import os

shapefile = "states.shp"
driver = ogr.GetDriverByName("ESRI Shapefile")
dataSource = driver.Open(shapefile, 0)
layer = dataSource.GetLayer()

wkt = "POLYGON ((-103.81402655265633 50.253951270672125,-102.94583419409656 51.535568561879401,-100.34125711841725 51.328856095555651,-100.34125711841725 51.328856095555651,-93.437060743203844 50.460663736995883,-93.767800689321859 46.450441890315041,-94.635993047881612 41.613370178339181,-100.75468205106476 41.365315218750681,-106.12920617548238 42.564247523428456,-105.96383620242338 47.277291755610058,-103.81402655265633 50.253951270672125))"
layer.SetSpatialFilter(ogr.CreateGeometryFromWkt(wkt))

for feature in layer:
    print feature.GetField("STATE_NAME")

Get Shapefile Fields - Get the user defined fields

This code example returns the field names of the user defined (created) fields.

from osgeo import ogr

daShapefile = r"C:\Temp\Voting_Centers_and_Ballot_Sites.shp"

dataSource = ogr.Open(daShapefile)
daLayer = dataSource.GetLayer(0)
layerDefinition = daLayer.GetLayerDefn()


for i in range(layerDefinition.GetFieldCount()):
    print layerDefinition.GetFieldDefn(i).GetName()

Get Shapefile Fields and Types - Get the user defined fields

This code example returns the field names of the user defined (created) fields and the data types they are.

from osgeo import ogr

daShapefile = r"C:\Temp\iDay\CWI_Wetlands.shp"

dataSource = ogr.Open(daShapefile)
daLayer = dataSource.GetLayer(0)
layerDefinition = daLayer.GetLayerDefn()


print "Name  -  Type  Width  Precision"
for i in range(layerDefinition.GetFieldCount()):
    fieldName =  layerDefinition.GetFieldDefn(i).GetName()
    fieldTypeCode = layerDefinition.GetFieldDefn(i).GetType()
    fieldType = layerDefinition.GetFieldDefn(i).GetFieldTypeName(fieldTypeCode)
    fieldWidth = layerDefinition.GetFieldDefn(i).GetWidth()
    GetPrecision = layerDefinition.GetFieldDefn(i).GetPrecision()

    print fieldName + " - " + fieldType+ " " + str(fieldWidth) + " " + str(GetPrecision)

Get PostGIS Layer Fields - Get the user defined fields

This code example returns the field names of the user defined (created) fields.

from osgeo import ogr
import sys

databaseServer = "<IP of database server OR Name of database server"
databaseName = "<Name of database>"
databaseUser = "<User name>"
databasePW = "<User password>"
connString = "PG: host=%s dbname=%s user=%s password=%s" %(databaseServer,databaseName,databaseUser,databasePW)


def GetPGLayerFields( lyr_name ):
    conn = ogr.Open(connString)

    lyr = conn.GetLayer( lyr_name )
    if lyr is None:
        print >> sys.stderr, '[ ERROR ]: layer name = "%s" could not be found in database "%s"' % ( lyr_name, databaseName )
        sys.exit( 1 )

    lyrDefn = lyr.GetLayerDefn()


    for i in range( lyrDefn.GetFieldCount() ):
        print lyrDefn.GetFieldDefn( i ).GetName()

    # Close connection
    conn = None


if __name__ == '__main__':

    if len( sys.argv ) < 2:
        print >> sys.stderr, '[ ERROR ]: you must pass at least one argument -- the layer name argument'
        sys.exit( 1 )

    lyr_name = sys.argv[1]
    GetPGLayerFields( lyr_name )

Get PostGIS Layer Fields and Types - Get the user defined fields

This code example returns the field names of the user defined (created) fields and the data types they are.

from osgeo import ogr
import sys


databaseServer = "<IP of database server OR Name of database server"
databaseName = "<Name of database>"
databaseUser = "<User name>"
databasePW = "<User password>"
connString = "PG: host=%s dbname=%s user=%s password=%s" %(databaseServer,databaseName,databaseUser,databasePW)


def GetPGLayerFieldTypes( lyr_name ):
    conn = ogr.Open(connString)

    lyr = conn.GetLayer( lyr_name )
    if lyr is None:
        print >> sys.stderr, '[ ERROR ]: layer name = "%s" could not be found in database "%s"' % ( lyr_name, databaseName )
        sys.exit( 1 )

    lyrDefn = lyr.GetLayerDefn()
    for i in range( lyrDefn.GetFieldCount() ):
        fieldName =  lyrDefn.GetFieldDefn(i).GetName()
        fieldTypeCode = lyrDefn.GetFieldDefn(i).GetType()
        fieldType = lyrDefn.GetFieldDefn(i).GetFieldTypeName(fieldTypeCode)
        fieldWidth = lyrDefn.GetFieldDefn(i).GetWidth()
        GetPrecision = lyrDefn.GetFieldDefn(i).GetPrecision()

        print fieldName + " - " + fieldType+ " " + str(fieldWidth) + " " + str(GetPrecision)

    # Close connection
    conn = None


if __name__ == '__main__':

    if len( sys.argv ) < 2:
        print >> sys.stderr, '[ ERROR ]: you must pass at least one argument -- the layer name argument'
        sys.exit( 1 )

    lyr_name = sys.argv[1]
    GetPGLayerFieldTypes( lyr_name )

Get a Layer's Capabilities

from osgeo import ogr

ds = ogr.Open("states.shp",0)
layer = ds.GetLayer()
capabilities = [
    ogr.OLCRandomRead,
    ogr.OLCSequentialWrite,
    ogr.OLCRandomWrite,
    ogr.OLCFastSpatialFilter,
    ogr.OLCFastFeatureCount,
    ogr.OLCFastGetExtent,
    ogr.OLCCreateField,
    ogr.OLCDeleteField,
    ogr.OLCReorderFields,
    ogr.OLCAlterFieldDefn,
    ogr.OLCTransactions,
    ogr.OLCDeleteFeature,
    ogr.OLCFastSetNextByIndex,
    ogr.OLCStringsAsUTF8,
    ogr.OLCIgnoreFields
]

print("Layer Capabilities:")
for cap in capabilities:
    print("  %s = %s" % (cap, layer.TestCapability(cap)))

Get WFS layers and iterate over features

This recipe queries a WFS services and fetches features from a large layer. It sets up the GDAL configuration to using WFS paging if it is supported.

import sys

try:
    from osgeo import ogr, osr, gdal
except:
    sys.exit('ERROR: cannot find GDAL/OGR modules')

# Set the driver (optional)
wfs_drv = ogr.GetDriverByName('WFS')

# Speeds up querying WFS capabilities for services with alot of layers
gdal.SetConfigOption('OGR_WFS_LOAD_MULTIPLE_LAYER_DEFN', 'NO')

# Set config for paging. Works on WFS 2.0 services and WFS 1.0 and 1.1 with some other services.
gdal.SetConfigOption('OGR_WFS_PAGING_ALLOWED', 'YES')
gdal.SetConfigOption('OGR_WFS_PAGE_SIZE', '10000')

# Open the webservice
url = 'http://example-service.com/wfs'
wfs_ds = wfs_drv.Open('WFS:' + url)
if not wfs_ds:
    sys.exit('ERROR: can not open WFS datasource')
else:
    pass

# iterate over available layers
for i in range(wfs_ds.GetLayerCount()):
    layer = wfs_ds.GetLayerByIndex(i)
    srs = layer.GetSpatialRef()
    print 'Layer: %s, Features: %s, SR: %s...' % (layer.GetName(), layer.GetFeatureCount(), srs.ExportToWkt()[0:50])

    # iterate over features
    feat = layer.GetNextFeature()
    while feat is not None:
        feat = layer.GetNextFeature()
        # do something more..
    feat = None

# Get a specific layer
layer = wfs_ds.GetLayerByName("largelayer")
if not layer:
    sys.exit('ERROR: can not find layer in service')
else:
    pass

Set HTTP Proxy options before fetching a web datasource

This recipe sets options for a HTTP proxy service that using NTLM authentication (typical for corporate environments that using Active directory for single sign-on proxy support). More information about the GDAL HTTP proxy options can be found here

import sys

try:
    from osgeo import ogr, osr, gdal
except:
    sys.exit('ERROR: cannot find GDAL/OGR modules')

server = 'proxy.example.com'
port = 3128

# specify proxy server
gdal.SetConfigOption('GDAL_HTTP_PROXY', server + ':' + port)

# setup proxy authentication option for NTLM with no username or password so single sign-on works
gdal.SetConfigOption('GDAL_PROXY_AUTH', 'NTLM')
gdal.SetConfigOption('GDAL_HTTP_PROXYUSERPWD', ' : ')

# now fetch a HTTP datasource and do something...
ds = ogr.Open('http://featureserver/cities/.geojson')
if not ds:
    sys.exit('ERROR: can not open GeoJSON datasource')
lyr = ds.GetLayer('OGRGeoJSON')
for feat in lyr:
    geom = feat.GetGeometryRef()
    print geom.ExportToWkt()

Read a CSV of Coordinates as an OGRVRTLayer

GDAL/OGR has a Virtual Format spec that allows you to derive layers from flat tables such as a CSV -- it does a lot more than that too so go read about it. In the example below we are reading in a CSV with X,Y columns and values. That CSV file is wrapped by an XML file that describes it as an OGR layer. Below are all the necessary pieces and a script that reads the XML file and prints out point geometries.

Our CSV file named example.csv looks like this:

ID,X,Y
1,-127.234343,47.234325
2,-127.003243,46.234343
3,-127.345646,45.234324
4,-126.234324,44.324234

Our OGRVRTLayer XML file called example_wrapper.vrt looks like this:

<OGRVRTDataSource>
    <OGRVRTLayer name="example">
        <SrcDataSource>example.csv</SrcDataSource>
        <SrcLayer>example</SrcLayer>
        <GeometryType>wkbPoint</GeometryType>
            <LayerSRS>WGS84</LayerSRS>
        <GeometryField encoding="PointFromColumns" x="X" y="Y"/>
    </OGRVRTLayer>
</OGRVRTDataSource>

Now let's print out the point geometries:

from osgeo import ogr
ogr.UseExceptions()

inDataSource = ogr.Open("example_wrapper.vrt")
lyr = inDataSource.GetLayer('example')
for feat in lyr:
    geom = feat.GetGeometryRef()
    print geom.ExportToWkt()

Create a new Layer from the extent of an existing Layer

from osgeo import ogr
import os

# Get a Layer's Extent
inShapefile = "states.shp"
inDriver = ogr.GetDriverByName("ESRI Shapefile")
inDataSource = inDriver.Open(inShapefile, 0)
inLayer = inDataSource.GetLayer()
extent = inLayer.GetExtent()

# Create a Polygon from the extent tuple
ring = ogr.Geometry(ogr.wkbLinearRing)
ring.AddPoint(extent[0],extent[2])
ring.AddPoint(extent[1], extent[2])
ring.AddPoint(extent[1], extent[3])
ring.AddPoint(extent[0], extent[3])
ring.AddPoint(extent[0],extent[2])
poly = ogr.Geometry(ogr.wkbPolygon)
poly.AddGeometry(ring)

# Save extent to a new Shapefile
outShapefile = "states_extent.shp"
outDriver = ogr.GetDriverByName("ESRI Shapefile")

# Remove output shapefile if it already exists
if os.path.exists(outShapefile):
    outDriver.DeleteDataSource(outShapefile)

# Create the output shapefile
outDataSource = outDriver.CreateDataSource(outShapefile)
outLayer = outDataSource.CreateLayer("states_extent", geom_type=ogr.wkbPolygon)

# Add an ID field
idField = ogr.FieldDefn("id", ogr.OFTInteger)
outLayer.CreateField(idField)

# Create the feature and set values
featureDefn = outLayer.GetLayerDefn()
feature = ogr.Feature(featureDefn)
feature.SetGeometry(poly)
feature.SetField("id", 1)
outLayer.CreateFeature(feature)
feature = None

# Save and close DataSource
inDataSource = None
outDataSource = None

Save the convex hull of all geometry from an input Layer to an output Layer

from osgeo import ogr
import os

# Get a Layer
inShapefile = "states.shp"
inDriver = ogr.GetDriverByName("ESRI Shapefile")
inDataSource = inDriver.Open(inShapefile, 0)
inLayer = inDataSource.GetLayer()

# Collect all Geometry
geomcol = ogr.Geometry(ogr.wkbGeometryCollection)
for feature in inLayer:
    geomcol.AddGeometry(feature.GetGeometryRef())

# Calculate convex hull
convexhull = geomcol.ConvexHull()

# Save extent to a new Shapefile
outShapefile = "states_convexhull.shp"
outDriver = ogr.GetDriverByName("ESRI Shapefile")

# Remove output shapefile if it already exists
if os.path.exists(outShapefile):
    outDriver.DeleteDataSource(outShapefile)

# Create the output shapefile
outDataSource = outDriver.CreateDataSource(outShapefile)
outLayer = outDataSource.CreateLayer("states_convexhull", geom_type=ogr.wkbPolygon)

# Add an ID field
idField = ogr.FieldDefn("id", ogr.OFTInteger)
outLayer.CreateField(idField)

# Create the feature and set values
featureDefn = outLayer.GetLayerDefn()
feature = ogr.Feature(featureDefn)
feature.SetGeometry(convexhull)
feature.SetField("id", 1)
outLayer.CreateFeature(feature)
feature = None

# Save and close DataSource
inDataSource = None
outDataSource = None

Save centroids of input Layer to an output Layer

Inspired by: http://www.kralidis.ca/blog/2010/04/28/batch-centroid-calculations-with-python-and-ogr/

from osgeo import ogr
import os

# Get the input Layer
inShapefile = "states.shp"
inDriver = ogr.GetDriverByName("ESRI Shapefile")
inDataSource = inDriver.Open(inShapefile, 0)
inLayer = inDataSource.GetLayer()

# Create the output Layer
outShapefile = "states_centroids.shp"
outDriver = ogr.GetDriverByName("ESRI Shapefile")

# Remove output shapefile if it already exists
if os.path.exists(outShapefile):
    outDriver.DeleteDataSource(outShapefile)

# Create the output shapefile
outDataSource = outDriver.CreateDataSource(outShapefile)
outLayer = outDataSource.CreateLayer("states_centroids", geom_type=ogr.wkbPoint)

# Add input Layer Fields to the output Layer
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()

# Add features to the ouput Layer
for i in range(0, inLayer.GetFeatureCount()):
    # Get the input Feature
    inFeature = inLayer.GetFeature(i)
    # Create output Feature
    outFeature = ogr.Feature(outLayerDefn)
    # Add field values from input Layer
    for i in range(0, outLayerDefn.GetFieldCount()):
        outFeature.SetField(outLayerDefn.GetFieldDefn(i).GetNameRef(), inFeature.GetField(i))
    # Set geometry as centroid
    geom = inFeature.GetGeometryRef()
    inFeature = None
    centroid = geom.Centroid()
    outFeature.SetGeometry(centroid)
    # Add new feature to output Layer
    outLayer.CreateFeature(outFeature)
    outFeature = None

# Save and close DataSources
inDataSource = None
outDataSource = None

Create a New Shapefile and Add Data

This recipe parses a delimited text file of volcano location data and creates a shapefile. The CSV file volcano_data.txt contains the following fields, separated by a tab character (\t):

• Name
• Region
• Latitude
• Longitude
• Elevation

Taken from The Geospatial Desktop book.

# Parse a delimited text file of volcano data and create a shapefile

import osgeo.ogr as ogr
import osgeo.osr as osr

# use a dictionary reader so we can access by field name
reader = csv.DictReader(open("volcano_data.txt","rb"),
    delimiter='\t',
    quoting=csv.QUOTE_NONE)

# set up the shapefile driver
driver = ogr.GetDriverByName("ESRI Shapefile")

# create the data source
data_source = driver.CreateDataSource("volcanoes.shp")

# create the spatial reference, WGS84
srs = osr.SpatialReference()
srs.ImportFromEPSG(4326)

# create the layer
layer = data_source.CreateLayer("volcanoes", srs, ogr.wkbPoint)

# Add the fields we're interested in
field_name = ogr.FieldDefn("Name", ogr.OFTString)
field_name.SetWidth(24)
layer.CreateField(field_name)
field_region = ogr.FieldDefn("Region", ogr.OFTString)
field_region.SetWidth(24)
layer.CreateField(field_region)
layer.CreateField(ogr.FieldDefn("Latitude", ogr.OFTReal))
layer.CreateField(ogr.FieldDefn("Longitude", ogr.OFTReal))
layer.CreateField(ogr.FieldDefn("Elevation", ogr.OFTInteger))

# Process the text file and add the attributes and features to the shapefile
for row in reader:
  # create the feature
  feature = ogr.Feature(layer.GetLayerDefn())
  # Set the attributes using the values from the delimited text file
  feature.SetField("Name", row['Name'])
  feature.SetField("Region", row['Region'])
  feature.SetField("Latitude", row['Latitude'])
  feature.SetField("Longitude", row['Longitude'])
  feature.SetField("Elevation", row['Elev'])

  # create the WKT for the feature using Python string formatting
  wkt = "POINT(%f %f)" %  (float(row['Longitude']) , float(row['Latitude']))

  # Create the point from the Well Known Txt
  point = ogr.CreateGeometryFromWkt(wkt)

  # Set the feature geometry using the point
  feature.SetGeometry(point)
  # Create the feature in the layer (shapefile)
  layer.CreateFeature(feature)
  # Dereference the feature
  feature = None

# Save and close the data source
data_source = None

Create a PostGIS table from WKT

This recipe creates a new table in an existing PostGIS database.

import ogr, osr

database = 'test'
usr = 'postgres'
pw = ''
table = 'test'

wkt = "POINT (1120351.5712494177 741921.4223245403)"
point = ogr.CreateGeometryFromWkt(wkt)

connectionString = "PG:dbname='%s' user='%s' password='%s'" % (database,usr,pw)
ogrds = ogr.Open(connectionString)

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

layer = ogrds.CreateLayer(table, srs, ogr.wkbPoint, ['OVERWRITE=YES'] )

layerDefn = layer.GetLayerDefn()

feature = ogr.Feature(layerDefn)
feature.SetGeometry(point)

layer.StartTransaction()
layer.CreateFeature(feature)
feature = None
layer.CommitTransaction()

Filter and Select Input Shapefile to New Output Shapefile Like ogr2ogr CLI

The ogr2ogr command line tool is an easy way to filter, reproject and trim columns in a shapefile. The workflow below shows how we can approximate the following ogr2ogr command with the OGR api using a decently large parcel shapefile from King County GIS .

#
# this command says read in "parcel_address.shp" and write out to "junkmob.shp"
# where "MINOR" column = 'HYDR' value and only output the "PIN" column
#
$ ogr2ogr -f "ESRI Shapefile" junkmob.shp -select pin -where "minor = 'HYDR'" parcel_address.shp

from osgeo import ogr
import os, sys

def main( field_name_target ):
    # Get the input Layer
    inShapefile = "~/DATA/SHAPES/KC_ADMIN/parcel_address/parcel_address.shp"
    inDriver = ogr.GetDriverByName("ESRI Shapefile")
    inDataSource = inDriver.Open(inShapefile, 0)
    inLayer = inDataSource.GetLayer()
    inLayer.SetAttributeFilter("minor = 'HYDR'")

    # Create the output LayerS
    outShapefile = os.path.join( os.path.split( inShapefile )[0], "ogr_api_filter.shp" )
    outDriver = ogr.GetDriverByName("ESRI Shapefile")

    # Remove output shapefile if it already exists
    if os.path.exists(outShapefile):
        outDriver.DeleteDataSource(outShapefile)

    # Create the output shapefile
    outDataSource = outDriver.CreateDataSource(outShapefile)
    out_lyr_name = os.path.splitext( os.path.split( outShapefile )[1] )[0]
    outLayer = outDataSource.CreateLayer( out_lyr_name, geom_type=ogr.wkbMultiPolygon )

    # Add input Layer Fields to the output Layer if it is the one we want
    inLayerDefn = inLayer.GetLayerDefn()
    for i in range(0, inLayerDefn.GetFieldCount()):
        fieldDefn = inLayerDefn.GetFieldDefn(i)
        fieldName = fieldDefn.GetName()
        if fieldName not in field_name_target:
            continue
        outLayer.CreateField(fieldDefn)

    # Get the output Layer's Feature Definition
    outLayerDefn = outLayer.GetLayerDefn()

    # Add features to the ouput Layer
    for inFeature in inLayer:
        # Create output Feature
        outFeature = ogr.Feature(outLayerDefn)

        # Add field values from input Layer
        for i in range(0, outLayerDefn.GetFieldCount()):
            fieldDefn = outLayerDefn.GetFieldDefn(i)
            fieldName = fieldDefn.GetName()
            if fieldName not in field_name_target:
                continue

            outFeature.SetField(outLayerDefn.GetFieldDefn(i).GetNameRef(),
                inFeature.GetField(i))

        # Set geometry as centroid
        geom = inFeature.GetGeometryRef()
        outFeature.SetGeometry(geom.Clone())
        # Add new feature to output Layer
        outLayer.CreateFeature(outFeature)
        outFeature = None

    # Save and close DataSources
    inDataSource = None
    outDataSource = None

if __name__ == '__main__':

    if len( sys.argv ) < 2:
        print "[ ERROR ]: you need to pass at least one arg -- the field_names to include in output"
        sys.exit(1)

    main( sys.argv[1:] )

Merge OGR Layers

This recipe merges OGR Layers within a directory. Files can be specfied based on with what they start and end.

import os, ogr, osr

outputMergefn = 'merge.shp'
directory = "/Users/UserName/Downloads/"
fileStartsWith = 'test'
fileEndsWith = '.shp'
driverName = 'ESRI Shapefile'
geometryType = ogr.wkbPolygon

out_driver = ogr.GetDriverByName( driverName )
if os.path.exists(outputMergefn):
    out_driver.DeleteDataSource(outputMergefn)
out_ds = out_driver.CreateDataSource(outputMergefn)
out_layer = out_ds.CreateLayer(outputMergefn, geom_type=geometryType)

fileList = os.listdir(directory)

for file in fileList:
    if file.startswith(fileStartsWith) and file.endswith(fileEndsWith):
        print file
        ds = ogr.Open(directory+file)
        lyr = ds.GetLayer()
        for feat in lyr:
            out_feat = ogr.Feature(out_layer.GetLayerDefn())
            out_feat.SetGeometry(feat.GetGeometryRef().Clone())
            out_layer.CreateFeature(out_feat)
            out_feat = None
            out_layer.SyncToDisk()

Get a list of the street names in a OSM file

This recipe takes in an OSM file and prints a list of all the names of the streets in the file.

import ogr

ds = ogr.Open('map.osm')
layer = ds.GetLayer(1) # layer 1 for ways

nameList = []
for feature in layer:
    if feature.GetField("highway") != None:  # only streets
        name = feature.GetField("name")
        if name != None and name not in nameList: # only streets that have a name and are not yet in the list
            nameList.append(name)

print nameList

Create fishnet grid

This recipe creates a fishnet grid.

python grid.py grid.shp 992325.66 1484723.41 494849.32 781786.14 10000 10000

import os, sys
import ogr
from math import ceil


def main(outputGridfn,xmin,xmax,ymin,ymax,gridHeight,gridWidth):

    # convert sys.argv to float
    xmin = float(xmin)
    xmax = float(xmax)
    ymin = float(ymin)
    ymax = float(ymax)
    gridWidth = float(gridWidth)
    gridHeight = float(gridHeight)

    # get rows
    rows = ceil((ymax-ymin)/gridHeight)
    # get columns
    cols = ceil((xmax-xmin)/gridWidth)

    # start grid cell envelope
    ringXleftOrigin = xmin
    ringXrightOrigin = xmin + gridWidth
    ringYtopOrigin = ymax
    ringYbottomOrigin = ymax-gridHeight

    # create output file
    outDriver = ogr.GetDriverByName('ESRI Shapefile')
    if os.path.exists(outputGridfn):
        os.remove(outputGridfn)
    outDataSource = outDriver.CreateDataSource(outputGridfn)
    outLayer = outDataSource.CreateLayer(outputGridfn,geom_type=ogr.wkbPolygon )
    featureDefn = outLayer.GetLayerDefn()

    # create grid cells
    countcols = 0
    while countcols < cols:
        countcols += 1

        # reset envelope for rows
        ringYtop = ringYtopOrigin
        ringYbottom =ringYbottomOrigin
        countrows = 0

        while countrows < rows:
            countrows += 1
            ring = ogr.Geometry(ogr.wkbLinearRing)
            ring.AddPoint(ringXleftOrigin, ringYtop)
            ring.AddPoint(ringXrightOrigin, ringYtop)
            ring.AddPoint(ringXrightOrigin, ringYbottom)
            ring.AddPoint(ringXleftOrigin, ringYbottom)
            ring.AddPoint(ringXleftOrigin, ringYtop)
            poly = ogr.Geometry(ogr.wkbPolygon)
            poly.AddGeometry(ring)

            # add new geom to layer
            outFeature = ogr.Feature(featureDefn)
            outFeature.SetGeometry(poly)
            outLayer.CreateFeature(outFeature)
            outFeature = None

            # new envelope for next poly
            ringYtop = ringYtop - gridHeight
            ringYbottom = ringYbottom - gridHeight

        # new envelope for next poly
        ringXleftOrigin = ringXleftOrigin + gridWidth
        ringXrightOrigin = ringXrightOrigin + gridWidth

    # Save and close DataSources
    outDataSource = None


if __name__ == "__main__":

    #
    # example run : $ python grid.py <full-path><output-shapefile-name>.shp xmin xmax ymin ymax gridHeight gridWidth
    #

    if len( sys.argv ) != 8:
        print "[ ERROR ] you must supply seven arguments: output-shapefile-name.shp xmin xmax ymin ymax gridHeight gridWidth"
        sys.exit( 1 )

    main( sys.argv[1], sys.argv[2], sys.argv[3], sys.argv[4], sys.argv[5], sys.argv[6], sys.argv[7] )

Convert polygon shapefile to line shapefile

This recipe converts a poylgon shapefile to a line shapefile

import ogr, os

def poly2line(input_poly,output_line):

    source_ds = ogr.Open(input_poly)
    source_layer = source_ds.GetLayer()

    # polygon2geometryCollection
    geomcol =  ogr.Geometry(ogr.wkbGeometryCollection)
    for feat in source_layer:
        geom = feat.GetGeometryRef()
        ring = geom.GetGeometryRef(0)
        geomcol.AddGeometry(ring)

    # geometryCollection2shp
    shpDriver = ogr.GetDriverByName("ESRI Shapefile")
    if os.path.exists(output_line):
            shpDriver.DeleteDataSource(output_line)
    outDataSource = shpDriver.CreateDataSource(output_line)
    outLayer = outDataSource.CreateLayer(output_line, geom_type=ogr.wkbMultiLineString)
    featureDefn = outLayer.GetLayerDefn()
    outFeature = ogr.Feature(featureDefn)
    outFeature.SetGeometry(geomcol)
    outLayer.CreateFeature(outFeature)
    outFeature = None

def main(input_poly,output_line):
    poly2line(input_poly,output_line)

if __name__ == "__main__":
    input_poly = 'test_polygon.shp'
    output_line = 'test_line.shp'

    main(input_poly,output_line)

Create point shapefile with attribute data

This recipe creates a new shapefiles, adds a point to it, and adds a attribute column with a value to it.

    import ogr, os

    # Input data
    pointCoord = -124.4577,48.0135
    fieldName = 'test'
    fieldType = ogr.OFTString
    fieldValue = 'test'
    outSHPfn = 'test.shp'

    # Create the output shapefile
    shpDriver = ogr.GetDriverByName("ESRI Shapefile")
    if os.path.exists(outSHPfn):
        shpDriver.DeleteDataSource(outSHPfn)
    outDataSource = shpDriver.CreateDataSource(outSHPfn)
    outLayer = outDataSource.CreateLayer(outSHPfn, geom_type=ogr.wkbPoint )

    #create point geometry
    point = ogr.Geometry(ogr.wkbPoint)
    point.AddPoint(pointCoord[0],pointCoord[1])

    # create a field
    idField = ogr.FieldDefn(fieldName, fieldType)
    outLayer.CreateField(idField)

    # Create the feature and set values
    featureDefn = outLayer.GetLayerDefn()
    outFeature = ogr.Feature(featureDefn)
    outFeature.SetGeometry(point)
    outFeature.SetField(fieldName, fieldValue)
    outLayer.CreateFeature(outFeature)
outFeature = None

Create buffer

This recipe buffers features of a layer and saves them to a new Layer

import ogr, os

def createBuffer(inputfn, outputBufferfn, bufferDist):
    inputds = ogr.Open(inputfn)
    inputlyr = inputds.GetLayer()

    shpdriver = ogr.GetDriverByName('ESRI Shapefile')
    if os.path.exists(outputBufferfn):
        shpdriver.DeleteDataSource(outputBufferfn)
    outputBufferds = shpdriver.CreateDataSource(outputBufferfn)
    bufferlyr = outputBufferds.CreateLayer(outputBufferfn, geom_type=ogr.wkbPolygon)
    featureDefn = bufferlyr.GetLayerDefn()

    for feature in inputlyr:
        ingeom = feature.GetGeometryRef()
        geomBuffer = ingeom.Buffer(bufferDist)

        outFeature = ogr.Feature(featureDefn)
        outFeature.SetGeometry(geomBuffer)
        bufferlyr.CreateFeature(outFeature)
        outFeature = None

def main(inputfn, outputBufferfn, bufferDist):
    createBuffer(inputfn, outputBufferfn, bufferDist)


if __name__ == "__main__":
    inputfn = 'test.shp'
    outputBufferfn = 'testBuffer.shp'
    bufferDist = 10.0

    main(inputfn, outputBufferfn, bufferDist)

Convert vector layer to array

This recipe converts a vector layer to an array.

[[0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 0 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0]
 [0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0]
 [0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
 [0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
 [0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
 [0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
 [0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0]
 [0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0]
 [0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0]
 [0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0]
 [0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0]
 [0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0]
 [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0]
 [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0]
 [0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0]
 [0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0]
 [0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0]]

import ogr, gdal

vector_fn = 'test.shp'

# Define pixel_size and NoData value of new raster
pixel_size = 25
NoData_value = 255

# Open the data source and read in the extent
source_ds = ogr.Open(vector_fn)
source_layer = source_ds.GetLayer()
source_srs = source_layer.GetSpatialRef()
x_min, x_max, y_min, y_max = source_layer.GetExtent()

# Create the destination data source
x_res = int((x_max - x_min) / pixel_size)
y_res = int((y_max - y_min) / pixel_size)
target_ds = gdal.GetDriverByName('MEM').Create('', x_res, y_res, gdal.GDT_Byte)
target_ds.SetGeoTransform((x_min, pixel_size, 0, y_max, 0, -pixel_size))
band = target_ds.GetRasterBand(1)
band.SetNoDataValue(NoData_value)

# Rasterize
gdal.RasterizeLayer(target_ds, [1], source_layer, burn_values=[1])

# Read as array
array = band.ReadAsArray()
print array

Convert polygon to points

This recipe converts a polygon to points.

import ogr, gdal
import numpy as np
import os

polygon_fn = 'test_polygon.shp'

# Define pixel_size which equals distance betweens points
pixel_size = 10

# Open the data source and read in the extent
source_ds = ogr.Open(polygon_fn)
source_layer = source_ds.GetLayer()
x_min, x_max, y_min, y_max = source_layer.GetExtent()

# Create the destination data source
x_res = int((x_max - x_min) / pixel_size)
y_res = int((y_max - y_min) / pixel_size)
target_ds = gdal.GetDriverByName('GTiff').Create('temp.tif', x_res, y_res, gdal.GDT_Byte)
target_ds.SetGeoTransform((x_min, pixel_size, 0, y_max, 0, -pixel_size))
band = target_ds.GetRasterBand(1)
band.SetNoDataValue(255)

# Rasterize
gdal.RasterizeLayer(target_ds, [1], source_layer, burn_values=[1])

# Read as array
array = band.ReadAsArray()

raster = gdal.Open('temp.tif')
geotransform = raster.GetGeoTransform()

# Convert array to point coordinates
count = 0
roadList = np.where(array == 1)
multipoint = ogr.Geometry(ogr.wkbMultiPoint)
for indexY in roadList[0]:
    indexX = roadList[1][count]
    geotransform = raster.GetGeoTransform()
    originX = geotransform[0]
    originY = geotransform[3]
    pixelWidth = geotransform[1]
    pixelHeight = geotransform[5]
    Xcoord = originX+pixelWidth*indexX
    Ycoord = originY+pixelHeight*indexY
    point = ogr.Geometry(ogr.wkbPoint)
    point.AddPoint(Xcoord, Ycoord)
    multipoint.AddGeometry(point)
    count += 1

# Write point coordinates to Shapefile
shpDriver = ogr.GetDriverByName("ESRI Shapefile")
if os.path.exists('points.shp'):
    shpDriver.DeleteDataSource('points.shp')
outDataSource = shpDriver.CreateDataSource('points.shp')
outLayer = outDataSource.CreateLayer('points.shp', geom_type=ogr.wkbMultiPoint)
featureDefn = outLayer.GetLayerDefn()
outFeature = ogr.Feature(featureDefn)
outFeature.SetGeometry(multipoint)
outLayer.CreateFeature(outFeature)
outFeature = None

# Remove temporary files
os.remove('temp.tif')