[gdal-dev] Re: Transform not working

[deadpickle]

Not much of a response going on here. In order to change the shapefile
projection from geographic to projected do I need to reopen the file,
get each feature, and transform the points individually? If so what
calls do I need to invoke?

On Mar 1, 12:54 pm, Jamie Lahowetz <deadpic... at gmail.com> wrote:
> I'm new to GDAL and am usingthe python bindings. I want to transform a newly
> created shapefile from WGS84 to a Lambert Conical Conformal so that I can
> calculate the length of the contained polylines. The script exits with no
> errors but when I look at the shapefile in arcCatalog I see that the
> projection is still WGS84. Any ideas? Also, is there a way to calculate the
> length directly from GDAL? Thanks.
>
> import os
> try:
>     from osgeo import ogr
>     from osgeo import osr
>
> except:
>     import ogr
>     import osr
>
> #~ start driver
> driver = ogr.GetDriverByName('ESRI Shapefile')
> #~ set workspace
> ws = 'C:\\Users\\deadpickle\\
> Desktop\\case study\\verify\\'
> os.chdir(ws)
>
> #~ check if it exists
> if os.path.exists('test.shp'):
>     driver.DeleteDataSource('test.shp')
>
> #~ create a new shp
> ds = driver.CreateDataSource('test.shp')
>
> #~ create spatref for new shp
> source = osr.SpatialReference()
> source.SetFromUserInput('WGS84')
>
> #~ create a new data layer
> layer = ds.CreateLayer('test',geom_type=ogr.wkbLineString,srs=source)
>
> #~ add an id field
> fieldDefn = ogr.FieldDefn('id', ogr.OFTInteger)
> layer.CreateField(fieldDefn)
>
> #~ create a geometry
> line = ogr.Geometry(ogr.wkbLineString)
>
> #~ get the def of the layer, scheme
> featureDefn = layer.GetLayerDefn()
>
> # create a new feature
> feature = ogr.Feature(featureDefn)
>
> #~ Read 2006track file
> file = open("2006track.csv","r")
> file.readline()
> lnlist = file.readlines()
> for lines in lnlist:
>     value = lines.split(",")
>     if float(value[1]) == 2:
>         print value
>         line.AddPoint(float(value[3]),float(value[2]))
>         #~ set the field 'ID'
>         feature.SetField('id', float(value[1]))
>
> #~ set the geometry for this shp
> feature.SetGeometry(line)
>
> # add the feature to the output layer
> layer.CreateFeature(feature)
>
> #~ feature = layer.GetFeature(0)
> geom = feature.GetGeometryRef()
>
> #~ change projection to lcc
> target = osr.SpatialReference()
> target.ImportFromProj4('+proj=lcc +lat_1= 33.000000 +lat_2=45.000000
> +lat_0=39.000000 +lon_0=-96.000000 +x_0=0.0 +y_0=0.0')
> coordtrans = osr.CoordinateTransformation(source, target)
>
> geom.Transform(coordtrans)
>
> # destroy the geometry and feature and close the data source
>
> ds.Destroy()
> line.Destroy()
> feature.Destroy()
> file.close()
>
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