Putting the map into OSM:
rendering geo-data with Mapnik

Artem Pavlenkomapnik.org

A brief history of (web)mapping

Good old 70s GIS

OGC WMS, WFS, W*S ...

Google Maps

[???]

Why did I like Google Maps?

No Java, no Flash, no ActiveX

No W*S

Lots of data

Good looking maps

APIs

What was the problem, then?

It is not free!

Data is subject to license and rendering software is proprietary

Searching for the solution

In the post GMap world we expect web mapping to be:

Fast

Highly interactive

And to have good cartography

At the time, none of the FOSS tools delivered these...

Mapnik

Mapnik is not ...

GIS

A map server, though you can hack one with Mapnik in no time

Attempt to implement all OGC specs in Java and bully the rest for not doing so

MapNick I'm not Nick ...

Mapnik is ...

About making beautiful maps

What I wanted to use myself

F/OSS

Cross platform Linux, Mac OS X, Win32

Written in modern c++

Easy to get started (Python bindings)

Flexible design

How do you make a map?

Making a map is easy

from mapnik import *

m = Map(800,600)

load_map(m,'/Users/artem/map.xml')

m.zoom_to_box(Envelope(-180,-90,180,90))

render_to_file(m,"world.jpg","jpeg")

What is *.xml?

Making a map is easy

Making a map is easy

Making a map is easy (almost)

lightgrey

white

MyStyle

Making a map is fun

from mapnik import *

m = Map(800,600,"+proj=latlong +datum=WGS84")

m.background = Color('steelblue')

s = Style()

r=Rule()

r.symbols.append(PolygonSymbolizer(Color('#f2eff9')))

r.symbols.append(LineSymbolizer(Color('rgb(50%,50%,50%)'),0.1))

s.rules.append(r)

m.append_style('My Style')

lyr = Layer('world')

lyr.datasource Shapefile(file='/opt/data/countries')

lyr.styles.append('My Style')

m.layers.append(lyr)

m.zoom_to_box(lyr.envelope())

render_to_file(m,'world.jpg', 'jpeg')

Made it!

More about styling...

Named styles, each layer can have 0...N style(s)

Order is important 'painter model'

0...N Styles -> 0...N Rules ->(Min/Max Scale Denominator, Filter, 0...N Symbolizer(s))

Filter is 'filter expression'

Filter expressions - DSEL

Syntax for filter expressions is very simple, you enclose variables (evaluated at runtime) in square brackets - [var]

Arithmetics: + , - , * , /

Comparison: = , , > , < , >= , 1000 and [area]