[GIS] How to use OGR Simplify in Python

ogrpython-2.7simplify

I am trying to simplify several polygons part of one shapefile using Python and OGR. However, I am stuck with how to use the simplify function as mentioned in the documentation:

http://www.gdal.org/classOGRGeometry.html#a0f4d7948332d9efd6548e1cf87bb6c8f

I tried this, for example:

data = ogr.Simplify(inData)

But then I get an AttributeError:

'module' object has no attribute 'Simplify'

Any tips?

Best Answer

If you look at the link you provided, you will see that Simplify is a method of the OGRGeometry class. In Python, Simplify is a method (member-function) of ogr.Geometry.

OGRGeometry * OGRGeometry::Simplify ( double  dTolerance ) const


#! /usr/bin/python
import ogr

shp = ogr.Open('input.shp', 0)
lyr = shp.GetLayer()
feat = lyr.GetFeature(0)
geom = feat.geometry()
simple = geom.Simplify(2.0)

Related Solutions

OGR Erase Method in Python – Detailed Guide

Here is the tool like it is it in ESRI. the input driver could be modified to your needs. Also no projection is enforced on the output currently.

def erase(baseFile, eraseFile, outFile): #this class performs the erase tool from ARCGIS//     erasefile must be polygon
  import os
  import sys
  import functions

  try:
    from osgeo import ogr
  except ImportError:
    import ogr

  driver = ogr.GetDriverByName('Mapinfo File')
  driver2 = ogr.GetDriverByName('ESRI Shapefile')

  feat1 = driver.Open(baseFile, 0)
  if feat1 is None:
    print 'Could not open feat1.tab'
    sys.exit(1)

  feat2 = driver2.Open(eraseFile, 0)
  if feat2 is None:
    print 'Could not open feat2.tab'
    sys.exit(1)  

  feat1Layer = feat1.GetLayer()
  feat2Layer = feat2.GetLayer()

  feature2 = feat2Layer.GetFeature(0)
  geomfeat2 = feature2.GetGeometryRef()

  feat1Layer.ResetReading()

  # create a new data source and layer
  fn = outFile
  if os.path.exists(fn):
    driver.DeleteDataSource(fn)
  outDS = driver.CreateDataSource(fn)
  if outDS is None:
    print 'Could not create file'
    sys.exit(1)
  outLayer = outDS.CreateLayer('roads', geom_type=ogr.wkbLineString)

  functions.copyFields(feat1Layer, outLayer)
  # get the FeatureDefn for the output shapefile
  featureDefn = outLayer.GetLayerDefn()

  #loop through input layer
  for inFeature in feat1Layer: 

    # create a new feature
    outFeature = ogr.Feature(featureDefn)

    # copy the attributes and set geometry
    functions.copyAttributes(inFeature, outFeature)

    #get Geometry of feature and apply the difference method on that feature
    inGeom = inFeature.GetGeometryRef()
    GeomDiff = inGeom.Difference(geomfeat2)
    #Set geometry of the outfeature
    outFeature.SetGeometry(GeomDiff)

    # add the feature to the output layer
    outLayer.CreateFeature(outFeature)

Shapely – How to Measure Distance Using Shapely in Python

Your capital_pt is the coords attribute of the original capital shapely geometry object. In itself this is not a shapely geometry, rather a sequence of tuples of flots which are the point objects. Instead you should be using

distance_between_pts = capital.distance(city_items)

Given your case where you're trying to calculate distances for all points in a dataset opened by fiona, a quick example might help also:

import fiona
import shapely.geometry

# capital is a shapely geometry object

with fiona.open(path_to_data) as src:
    for feature in src:
        geom = shapely.geometry.shape(feature["geometry"])
        distance_between_pts = capital.distance(geom)
        print(distance_between_pts)

Best Answer

Related Solutions

OGR Erase Method in Python – Detailed Guide

Shapely – How to Measure Distance Using Shapely in Python

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