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Using GeoDjango for user participation in enriching web GIS systems

Using GeoDjango for user participation in enriching web GIS systems. Bo Zhao University of Florida July 15 th , 2009. Requests. So we need…. Web Framework PHP, ASP, Python , Java Geospatial libraries Commercial Geospatial libaries , Open Source libaries . Why Python Matters?.

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Using GeoDjango for user participation in enriching web GIS systems

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  1. Using GeoDjango for user participation in enriching web GIS systems Bo Zhao University of Florida July 15th, 2009

  2. Requests

  3. So we need… • Web Framework • PHP, ASP, Python, Java • Geospatial libraries • Commercial Geospatial libaries, Open Source libaries.

  4. Why Python Matters? • Glue Language • Dynamic script Language

  5. Open Source Geospatial Libs • Pros • Open source is very competitive for geospatial server software • Reduced total cost of ownership • Possibility that you own your own software • Better preparation for computing trends. • Cons • Limited technical support. • Adding Patches or updating might render to crash. • Possibility that you own your own software

  6. Why Geodjango?

  7. “Django is a high-level Python web framework that encourages rapid development and clean, pragmatic design.”

  8. Features of Django Framework • Object-relational mapper: Define your data models entirely in Python. You get a rich, dynamic database-access API, unnecessary to write SQL for query. • Template system: Use template language to separate design, content and Python code. • Automatic admin interface: Django does that automatically, and it's production-ready. • Elegant URL design: Design pretty URLs with no framework-specific limitations. Be as flexible as you like. • Cache system: cache frameworks for super performance. • Internationalization: Django has full support for multi-language applications.

  9. Design Pattern MTV Model Template View

  10. Model

  11. Object-relational mapping • Object-relational mapping (ORM) • a programming technique for converting data between incompatible type systems in relational databases and object-oriented programming languages. • ORM creates, in effect, a "virtual object database" that can be used from within the programming language.

  12. CREATE TABLE “hug_layer_world" ( "id" serial NOT NULL PRIMARY KEY, "name" varchar(300) NOT NULL, "geom" geometry NOT NULL, CONSTRAINT hug_layer_world_pkey PRIMARY KEY (hug_fid), CONSTRAINT enforce_dims_geom CHECK (ndims(geom) = 2), CONSTRAINT enforce_geotype_geom CHECK (geometrytype(geom) = 'MULTIPOLYGON'::text OR geom IS NULL), CONSTRAINT enforce_srid_geom CHECK (srid(geom) = 4326) );

  13. Scary Quirky Language • SQL knows no version control • Can be dangerous • DRY(Don’t Repeat Yourself.)

  14. from django.contrib.gis.db import models class LAYERS(models.Model): id = models.AutoField(primary_key=True) name = models.CharField(max_length=20) geom = models.MultiLineStringField(srid=4326) objects = models.GeoManager()

  15. SELECT "hug_layer_world"."id", "hug_layer_world".“name", "hug_layer_world".“geom" FROM ""hug_layer_world" WHERE "hug_layer_world"."name" = "China"; WORLD.objects.filter(title='China')

  16. Template DRY(Don’t repeat yourself)

  17. index.html <html> <head> <title> {% block title %}{% endblock %} </title> </head> <body> {% block content %}{% endblock %} </body> </html>

  18. tilecache.cfg [{{layer.name}}] url = {{layer.mf_url}} layers = {{layer.name}} spherical_mercator = {{layer.tc_spherical_mercator}} extension = {{layer.tc_extension}} metatile = {{layer.tc_metatile}} srs = EPSG:{{layer.tc_srs}} type = {{layer.tc_type}} searchable = {{layer.tc_searchable}} … …

  19. dataLayer.js amTemplates.{{layer.name}} = '<ul class="featureDetailList">' + {% for item in layer.alias %} {% ifnotequal item.name 'geom' %} '<li><label>{{item.alias}}</label><span> {{layer.left}}{{item.name}}{{layer.right}}</span></li>' + {% endifnotequal %} {% endfor %}'</ul>';

  20. View

  21. URLs

  22. /export.php?id=2&type=tilecache /upload.aspx?filetype=shapefile /export/tilecache/world/ /upload/shapefile/

  23. url.py • (r'^admin/upload/', 'upload_zipped_shapefiles.upload_zipfile'), • (r'^admin/export/$', 'export_config_files.index'), • (r'^databrowse/(.*)', databrowse.site.root), • (r'^map/(?P<path>.*)$', 'django.views.static.serve', {'document_root': settings.MAPS_DIR, 'show_indexes': True}),

  24. View functions def index(request): all_layers = LAYER.objects.all() all_maps = MAP.objects.all() return render_to_response('export.html', {'layers': all_layers, 'maps': all_maps, 'user': request.user})

  25. App

  26. world/ __init__.py admin.py models.py views.py templates/ layer_javascript.html layer_tilechache.html layer_mapfile.html

  27. Hands-on demo

  28. Thanks, any questions?

  29. References • http://www.djangoproject.com/ • Justin Bronn, Web Applications for (Neo)Geographers with Deadlines, Oct. 2008 • http://en.wikipedia.org/wiki/Object-relational_mapping

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