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Worskhop Leicester 2010


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Databases and Web Mapping the Open Source Way

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Worskhop Leicester 2010

  1. 1. Beyond Google Maps and Mashups
  2. 2. Practicalities ●Download: Save to /home/user and extract ● /home/user/leics2010 folder should then contain: ● shape_files (folder) mapserver.html baselayers.html leicester_2010_notes.pdf
  3. 3. Installing Quantum GIS plugins Needed Plugins: Mapserver Export, PostGIS manager, SPIT
  4. 4. Databases
  5. 5. Databases + ● Server-based database (not like access) ● Data is entirely separate from user interface ● Inside the database, data stored in schemas for finer control
  6. 6. How to connect to a database ● HOST: localhost,, ● DATABASE: ??? (your choice) ● USERNAME: user ● PASSWORD: user ● PORT: 5432 (default)
  7. 7. Getting spatial data into PostgreSQL ● OGR2OGR (command line) ● SHP2PGSQL (command line) ● SPIT plugin for Quantum GIS ● Essential Parameters: host, username, password, dbname, port (as before) ● Additionally: name and location of shapefile, name of table in database, coordinate system of data
  8. 8. Loading data with SPIT Create new database with pgadmin3 and connect to it with SPIT in QGIS
  9. 9. SPIT (continued) Make “DB Relation Name” all lower case!!!
  10. 10. Database house-keeping ● Each table should have a primary key ● Each spatial table should be recorded in the geometry_columns table ● Each spatial table should have a spatial index CREATE INDEX yourtable_idx ON yourtable USING GIST(geometry_column);
  11. 11. Querying data ● SQL: Structured Query Language SELECT some comma de-limited columns FROM your_table WHERE some condition is met; ● Use PSQL from command line, PgAdmin3, or PostgreSQL Manager/SQL Editor ● SQL is case-sensitive for table and column names, and keywords are usually in capitals
  12. 12. Querying data ● Display on the map using CREATE VIEW AS: CREATE VIEW viewname AS SELECT * FROM united_kingdom_counties WHERE... ● Add to QGIS using Add Layer/Add PostGIS layer
  13. 13. Spatial Querying ● Find out which county a point is in: SELECT “PROV3NAME” FROM united_kingdom_counties WHERE st_within(geomfromtext('point(-1.4 52.6)', 4326), the_geom); ● Find out the spatial extent of your data: SELECT st_extent(the_geom) FROM united_kingdom_counties;
  14. 14. Map Servers
  15. 15. Types of Map Server ● cgi program on a web server. Configuration via text files ● java-based program. Configuration via web interface
  16. 16. The Map File MAP NAME "sample" STATUS ON SIZE 600 400 EXTENT -180 -90 180 90 UNITS DD SHAPEPATH "../data" IMAGECOLOR 255 255 255 WEB IMAGEPATH "/ms4w/tmp/ms_tmp/" IMAGEURL "/ms_tmp/" END LAYER NAME 'global-raster' TYPE RASTER STATUS DEFAULT DATA bluemarble.gif END END
  17. 17. Checking and Viewing a map file ● SHP2IMG at the command line shp2img -m /home/user/leics2010/ -o /home/user/demo.png ● With a browser bin/mapserv? map=/home/user/leics2010/ &mode=map
  18. 18. Adding new layers to a mapfile LAYER NAME "your layer" STATUS DEFAULT TYPE POLYGON DATA "yourshapefile.shp" CLASS NAME "your name for this symbology" STYLE SYMBOL 0 OUTLINECOLOR 0 0 0 COLOR 207 150 123 END END END
  19. 19. Connecting to PostgreSQL from Mapserver LAYER NAME "UK Counties" STATUS DEFAULT TYPE POLYGON CONNECTIONTYPE POSTGIS CONNECTION "host=localhost port=5432 dbname=osgis2010 user=user password=user" DATA "the_geom from united_kingdom_counties" CLASS … END END
  20. 20. Displaying single layers ● Set the Layer status to “ON” rather than “DEFAULT” ● Specify the layers as part of the URL: http://localhost/cgi- bin/mapserv? map=/home/user/leics2010/demo. map&layer=counties
  21. 21. Web Mapping
  22. 22. Web Mapping: Practicalities ● Make the web folder writeable sudo chown -R user /var/www sudo chmod -R 755 /var/www ● If asked for a password, it's user
  23. 23. Structure of a web page <html> <head> <title> My Home Page </title> </head> <body> HELLO WORLD! </body> </html>
  24. 24. Scripting ● SERVER-SIDE: php, asp <?php phpinfo(); ?> ● CLIENT-SIDE: javascript
  25. 25. Solving Problems using Firefox
  26. 26. OpenLayers
  27. 27. OpenLayers page structure <html> <head> <script src="..lib/OpenLayers.js"></script> <script type="text/javascript"> var map, mylayer; function init() { map = new OpenLayers.Map('map'); mylayer = new OpenLayers.Layer.MapServer( "World Map", "http://localhost/cgi-bin/mapserv.exe", {map: 'C:/'}); map.addLayer(mylayer); map.zoomToMaxExtent(); } </script> </head> <body onload="init()"> <div id="map" style="width: 600px; height: 300px"></div> </body> </html>
  28. 28. Adding Controls Scale Bars, Permalink and Mouse Position Layer Switcher and Overview Map
  29. 29. Base Mapping ● Can use base data from Google, Microsoft, Yahoo, Openstreetmap, etc ● Specify base layer (not always necessary) {'isBaseLayer': true} ● Overlay needs to be transparent {'transparent':true, 'format': png} ● Change addlayers directive map.addLayers([layer1,layer2]);
  30. 30. Beyond OpenLayers •MapGuide Open Source •Mapfish •Mapchat •Featureserver
  31. 31. And Finally... Have fun!!! This work is licenced under the Creative Commons Attribution-Share Alike 2.0 UK: England & Wales License. To view a copy of this licence, visit or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California 94105, USA. Jo Cook OA Digital +44 (0)1524 880212