Shapefile Layers ¶

Upload a Shapefile to display on the map.

• Workflow Options
  • Import just to display as an overlay
  • Import into Native Tables via an XSL Transform
• Technology Options
  • Use the Python bindings for GDAL/OGR as we do for the GADM importer
  • Integrate ​Ogre to do the conversion
  • Integrate ​FeatureServer to do the conversion
  • Upload to a co-app & add a layer which accesses this via WMS/WFS (although the UI should show in the 'Shapefiles layers' section)
    • GeoServer
      • ​http://docs.geoserver.org/2.0.0/user/extensions/rest/rest-config-examples-curl.html#uploading-a-shapefile
      • ​https://github.com/dwins/gsconfig.py
    • ​MapServer
      • Build a .map file using ​Python MapScript

We can include ​TM_WORLD_BORDERS-0.3.zip as a useful base/sample

Import to display as an Overlay ¶

This is available as gis_layer_shapefile in Trunk

ToDo ¶

• Needs styling
  • Point layers should be possible to just use a marker (DONE)
    • Should be able to vary size based on an attribute
      • absolute values, such as 'Large', 'Medium' and 'Small'
      • value ranges, such as 0-5, 6-10, 21+
      Should be able to colour images based on an attribute (without needing coloured markers)
      • absolute values, such as 'Operational', 'Restricted' and 'Inoperable'
      • value ranges, such as 0-5, 6-10, 21+
  • Polygon layers (& optionally Point layers) can use a JSON Style object, as per Feature & Theme layers
    • Python side is done
    • Need to work in static/scripts/S3/s3.gis.layers.js
  • S3SQLCustomForm to include Style field from layer_config into main form
  • Graphical UI to adjust style
    • accessible from map
      • update map in real-time to see effect of sliders
    • accessible from catalogue (less important)
  • style.popup (like KML BalloonStyle?)
• Handle different projections
  • Currently this is supported by manually setting the projection (untested)
  • Can we read it from the Shapefile?
    • If doesn't yet exist in gis_projection, can we add a suitable record there? Download the appropriate proj4js support file?
• onaccept to write any modified data back to the attached shapefile
• Don't parse the Shapefile repeatedly if the file doesn't change
  • update_onaccept to check this & call main onaccept if it has

Import into native Tables ¶

SHP should be converted to an lxml.etree for import using XSLT.

Working sample script below has been started to be imported into the right place in Sahana here:

• ​https://github.com/flavour/eden/blob/master/modules/s3/codecs/shp.py#L228

'''
    Dump the contents of a shapefile to an lxml etree object
    Assumes the shapefile is encoded in UTF-8 format
    Tested with TM_WORLD_BORDERS-0.3.shp
'''

import sys
import ogr
import os

from lxml import etree

if len(sys.argv) != 2:
    print "Usage: importshape.py filename"
    sys.exit(0)

shapefilename = sys.argv[1]

layername = os.path.splitext(os.path.basename(shapefilename))[0]

# Create the datasource
ds = ogr.Open(shapefilename)

# Open the shapefile
if ds is None:
    print "Open failed.\n"
    sys.exit(0)

# Get the layer and iterate through the features
lyr = ds.GetLayer(0)

root = etree.Element("shapefile", name=layername)

for feat in lyr:

    featurenode = etree.SubElement(root, "feature")

    feat_defn = lyr.GetLayerDefn()

    for i in range(feat_defn.GetFieldCount()):

	field_defn = feat_defn.GetFieldDefn(i)

	fieldnode = etree.SubElement(featurenode, field_defn.GetName())

	if field_defn.GetType() == ogr.OFTInteger:
	    fieldnode.text = str(feat.GetFieldAsInteger(i))

	elif field_defn.GetType() == ogr.OFTReal:
	    fieldnode.text = str(feat.GetFieldAsDouble(i))

	elif field_defn.GetType() == ogr.OFTString:
	    FieldString = str(feat.GetFieldAsString(i))
	    fieldnode.text = FieldString.decode(encoding="UTF-8", errors="strict")

    wktnode = etree.SubElement(featurenode, "wkt")

    geom = feat.GetGeometryRef()	
    wktnode.text = geom.ExportToWkt()    

# Test the etree object
xmlString = etree.tostring(root, pretty_print=True)
f = open("test.xml","w")
f.write(xmlString)

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