Worskhop OSGIS2010

Databases and Web Mapping the Open Source Way
OSGIS 2010: Centre for Geospatial Sciences, Nottingham
June 2010

Jo Cook
OA Digital

j.cook@oadigital.net
01524 880212

Beyond Google Maps and Mashups

Practicalities

● Download:
www.archaeogeek.com/downloads/osgis2010.zip
●Save to /home/user and extract

●The folder /home/user/osgis2010 contain:

shape_files (folder)
demo.map
mapserver.html
baselayers.html
osgis_2010_notes.pdf (same as handout)

Introduction

3

2

1

Databases

+
www.postgresql.org
postgis.refractions.net
● Server-based database (not like access)
● Enterprise-level, with support for
transactions and multiple users

How to connect to a database

● HOST: localhost, 192.168.3.40, myserver.com
● DATABASE: ??? (your choice)
● USERNAME: user
● PASSWORD: user
● PORT: 5432 (default)

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)
name and location of shapefile, name of
table in database, coordinate system of
data

Installing Quantum GIS plugins

Loading data with SPIT

Create new database with pgadmin3
and connect to it with SPIT in QGIS

SPIT (continued)

Change to lower-case!

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);

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
● There is no escape from typing out your
query!

Spatial Querying

● Find out which county a point is in and
show it on the map:
CREATE VIEW whichcounty AS SELECT
“PROV3NAME” FROM
united_kingdom_counties WHERE
st_within(geomfromtext('point(-1.4
52.6)', 4326), the_geom);

Types of Map Server

● Minnesota Map Server (aka Mapserver)
cgi program on a web server.
Configuration via text files
● Geoserver
java-based program. Configuration via
web interface

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

Checking and Viewing a map file

● SHP2IMG at the command line
shp2img -m
/home/user/osgis2010/demo.map
-o /home/user/demo.png
● With a browser
http://localhost.com/cgi-
bin/mapserv?
map=/home/user/osgis2010/demo.map
&mode=map

Adding new layers to a mapfile

LAYER
NAME "your layer"
STATUS DEFAULT
TYPE POLYGON
DATA "yourshapefile.shp" (relative to the
“data” parameter in your mapfile)
CLASS
NAME "your name for this symbology"
OUTLINECOLOR 60 60 60
COLOR 255 255 0
SYMBOL 0
END
END

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/osgis2010/demo.
map&layer=layer1

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

Structure of a web page

<html>

<head>
<title> My Home Page
</title>
</head>

<body>
HELLO WORLD!
</body>

</html>

Scripting

● SERVER-SIDE:
php, asp
<?php
phpinfo();
?>
● CLIENT-SIDE:
javascript

Solving Problems using Firefox

Solving Problems using the mailing lists

RTFM j00 n00b!!!
• Get latest version of software
• Read the manual/help documentation
• Search the mailing list archives
• Strip as much detail out of your code as
possible
• Provide as much information as you can
about your setup and the steps you have
already taken

OpenLayers page structure
<html>
<head>
<script
src="http://www.openlayers.org/api/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:/world_mapfile.map'});
map.addLayer(mylayer);
map.zoomToMaxExtent();
}
</script>
</head>
<body onload="init()">
<div id="map" style="width: 600px; height: 300px"></div>
</body>
</html>

Adding Controls

Scale Bars, Permalink
and Mouse Position

Layer Switcher and
Overview Map

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]);

Beyond OpenLayers

•MapGuide Open Source
http://mapguide.osgeo.org
•Mapfish http://mapfish.org/
•Mapchat http://mapchat.ca/
•Featureserver http://featureserver.org/

And Finally...

Open Source Web Mapping is Great 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 http://creativecommons.org/licenses/by-sa/2.0/uk/ or send a letter to Creative
Commons, 171 Second Street, Suite 300, San Francisco, California
94105, USA.

Jo Cook
OA Digital
http://oadigital.net
j.cook@oadigital.net
+44 (0)1524 880212

Worskhop OSGIS2010

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