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<!DOCTYPE html>
<html>
<head>
<title>Title</title>
<meta charset="utf-8">
<style>
@import url(https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz);
@import url(https://fonts.googleapis.com/css?family=Droid+Serif:400,700,400italic);
@import url(https://fonts.googleapis.com/css?family=Ubuntu+Mono:400,700,400italic);
body { font-family: 'Droid Serif'; }
h1, h2, h3 {
font-family: 'Yanone Kaffeesatz';
font-weight: normal;
}
.remark-code, .remark-inline-code { font-family: 'Ubuntu Mono'; font-size: 1.1em }
.cols-three .colc { width: 33%; float: left; text-align: center}
.cols-three .col { width: 33%; float: left}
.cols-three .col2 { width: 66%; float: left}
.tlike { display: table }
.smallfont .remark-code { font-size: 0.92em }
.coltab { display : table-row }
.coltab .col20 { display : table-cell; width: 20% }
.coltab .col40 { display : table-cell; width: 40% }
.wd66 { width : 80% }
.large { font-size: 1.5em }
</style>
</head>
<body>
<textarea id="source">
class: center, middle
# Pyosmium
## Fast processing of OpenStreetMap data
<img src="pics/logo-pyosmium.svg" width="80">
Sarah Hoffmann
GeoPython 2017, Basel
---
# OpenStreetMap
.center[<img src="pics/osmmain.png" width="800">]
.center[Freely editable geo data]
---
# Osmium
- C++ library for reading and writing OSM data files
- collection of common functions for handling OSM data
- osmium-tool as command line tool for common tasks
# Pyosmium
- python bindings for Osmium (based on python-boost)
- quick prototyping
- access to libraries like shapely, numpy, psycopg2, ...
- still a **low-level** library
---
class: center, middle
## The Basics
---
# Pyosmium: Installation
## .center[pip install osmium]
### Linux, MacOS
- needs: Boost Python, Expat, Zlib, Bzlib
```
sudo apt-get install libboost-python-dev libexpat1-dev \
zlib1g-dev libbz2-dev
```
### Windows
- experimental wheels for Python 2.7 and 3.6 since version 2.12.2
---
# OSM: Basic Datatypes
#### Node - a WSG84 coordinate
.wd66[
```xml
<node id="2965" lat="51.513639" lon="-0.140043" .../>
```
]
#### Way - an ordered list of nodes
.wd66[
```xml
<way id="736446" ...>
<nd ref="822403"/>
<nd ref="21533912"/>
<nd ref="821601"/>
</way>
```
]
#### Relation - an ordered list of OSM objects with role
.wd66[
```xml
<relation id="92738476" ...>
<member type="node" ref="137632221" role="label"/>
<member type="way" ref="54637238" role="outer"/>
<member type="relation" ref="5481" role="subarea"/>
</relation>
```
]
---
# Example: Counting OSM objects
```py
import osmium
class FileStatsHandler(osmium.SimpleHandler):
def __init__(self):
super(FileStatsHandler, self).__init__()
self.count = [0, 0, 0]
def node(self, n):
self.count[0] += 1
def way(self, w):
self.count[1] += 1
def relation(self, r):
self.count[2] += 1
h = FileStatsHandler()
h.apply_file("switzerland-latest.osm.pbf")
print("Nodes: %d Ways: %d Relations: %d" % tuple(h.count))
```
---
# Pyosmium: SimpleHandler
#### Handler
```py
class Handler(osmium.SimpleHandler):
def __init__(self):
super(Handler, self).__init__()
```
- don't forget to call the derived constructor
- OSM file types: xml.gz, xml.bz2, **pbf**, o5m
#### Callbacks
```py
def object(self, o):
...
```
- available callback types: `node`, `way`, `relation`, `area`, `changeset`
- object parameter in callback is immutable
- object parameter is only valid in the scope of the callback!
---
class: center, middle
## Attributes
---
# OSM Data Attributes
- OSM: tags - key-value list of attributes
```xml
<way id="2965" ...>
<tag k="highway" v="motorway"/>
<tag k="name" v="Ostseeautobahn" />
<tag k="ref" v="A2" />
<tag k="bridge" v="yes" />
...
</node>
```
- Pyosmium: **`tags`** property
- dict-like immutable object
- use [] operator and get() function as accessor in the usual way
- bound to scope of object!
---
# Example: List of Most Common Street Names
```py
from collections import Counter
class StreetNames(osmium.SimpleHandler):
def __init__(self):
super(StreetNames, self).__init__()
self.names = Counter()
def way(self, w):
if 'highway' in w.tags:
self.names[w.tags.get('name', '<unknown>')] += 1
h = StreetNames()
h.apply_file("switzerland.osm.pbf")
for name,count in h.names.most_common(20):
print(count,name)
```
---
# OSM: Tagging Rules
.center[.large[There are no rules.]]
- no naming rules, just conventions
Reference: [wiki.openstreetmap.org](https:\\wiki.openstreetmap.org)
- relatively small list of 'primary keys':
`highway`, `amenity`, `building`, `railway`, `boundary`, `landuse`, `natural`,
`tourism`, ...
- other keys add additional information
`name`, `height`, `maxspeed`, `cusine`, `color`
- cross-check for usage statistics
Overview: [taginfo.openstreetmap.org](https:\\taginfo.openstreetmap.org)
.center[.large[Ignore what you don't know.]]
---
class: center, middle
## Geometries
---
# Nodes
- OSM: `lat`/`lon` attributes in WGS84
```xml
<node id="2965" lat="51.5173639" lon="-0.140043" ...>
</node>
```
- Pyosmium: **`node.location`** property
- `lat`/`lon` - as float
- `x`/`y` - as fixed-point integer with 7 digits after decimal point
- bound to scope of object!
---
# Lines
- OSM: ways only contain references to nodes
```xml
<way id="736446" ...>
<nd ref="822403"/>
<nd ref="21533912"/>
<nd ref="821601"/>
</way>
```
- Pyosmium: **`way.nodes`** property
- list of `NodeRef` objects, contains
- `ref` - the node id
- `location` - the node coordinate (if available)
- bound to scope of object!
- node locations must be cached and then added to way node reference list
---
# Example: Total Length of Motorways
```py
class RoadLengthHandler(osmium.SimpleHandler):
def __init__(self):
super(RoadLengthHandler, self).__init__()
self.length = 0.0
def way(self, w):
if w.tags.get('highway') == 'motorway':
try:
len = osmium.geom.haversine_distance(w.nodes)
if w.tags.get('oneway') != 'no':
len /= 2
self.length += len
except osmium.InvalidLocationError:
print("WARNING: way %d incomplete." % w.id)
h = RoadLengthHandler()
#### Set 'locations' to true to get way coordinates. ####
h.apply_file('switzerland.osm.pbf', locations=True)
print('Total way length: %.2f km' % (h.length/1000))
```
---
# OSM: Polygons
### From Ways
```py
def way(self, w):
is_building_polygon = w.is_closed() and 'building' in w.tags
```
- closed *and* has polygon-like tag
### From Relations
```py
def relation(self, r):
is_area = w.tags['type'] in ('multipolygon', 'boundary')
```
- type is boundary or multipolygon
- (multi)polygon outline consists of all ways in the relation
- OSM areas are not strictly OGC Simple Feature polygons
---
# Pyosmium: `area` callback
- returns
- closed ways (recheck your tags!)
- multipolygon relations
**Valid** geometries only!
- builds all polygon rings (OGC-compliant)
- functions:
- `from_way()`/`orig_id()` - source OSM object
- `outer_rings()`/`inner_rings()` - lists of rings of the polygon
- `area` callback automatically enables location cache
- rings are bound to scope of area!
---
# Example: Compute Area Size
```py
class AreaHandler(osmium.SimpleHandler):
def signed_ring_area(self, ring):
total = 0.0
prev = None
for nref in ring:
if prev is not None:
total += prev[0] * nref.lat - prev[1] * nref.lon
prev = (nref.lon, nref.lat)
return total/2
def area(self, a):
for r in a.outer_rings():
area += self.signed_ring_area(r)
for i in a.inner_rings(r):
area += self.signed_ring_area(i)
print('W' if a.from_way() else 'R', a.orig_id(), area)
```
---
class: middle, center
# Interfacing with Geometry-processing Libraries
---
# Pyosmium: Geometry Factories
- converters to well-known geometry formats
```py
wkb_fab = osmium.geom.WKBFactory()
wkt_fab = osmium.geom.WKTFactory()
geosjosn_fab = osmium.geom.GeoJSONFactory()
```
- functions for all datatypes
```py
point = wkb_fab.create_point(node)
line = wkb_fab.create_linestring(way)
polygon = wkb_fab.create_multipolygon(area)
```
---
# Example: Interfacing with Geos
```py
import shapely.wkb
wkbfab = osmium.geom.WKBFactory()
class AreaHandler(osmium.SimpleHandler):
def area(self, a):
# create WKB from area
wkb = wkbfab.create_multipolygon(a)
# load into shapely
poly = shapely.wkb.loads(wkb, hex=True)
print('W' if a.from_way() else 'R', a.orig_id(),
poly.area)
```
---
class: smallfont
# Example: Shapefile conversion with Fiona
```py
import fiona
import osmium
drv = 'ESRI Shapefile'
crs = {'no_defs': True, 'ellps': 'WGS84', 'datum': 'WGS84', 'proj': 'longlat'}
schema = {'geometry': 'LineString',
'properties': {'id': 'float', 'name' : 'str', 'kind' : 'str'}}
outfile = fiona.open('test.shp', 'w', driver=drv, crs=crs, schema=schema)
geomfab = osmium.geom.GeoJSONFactory()
class ShapeConverter(osmium.SimpleHandler):
def way(self, w):
if 'waterway' in w.tags:
rec = {'geometry' : eval(geomfab.create_linestring(w)),
'properties' : {'id' : float(w.id),
'name' : w.tags.get('name'),
'kind' : w.tags['waterway']}}
outfile.write(rec)
ShapeConverter().apply_file("switzerland.osm.pbf", locations=True)
```
---
class: middle, center
# Writing OSM files
---
# Pyosmium: SimpleWriter
```py
osmium.SimpleWriter(<filename>)
```
- writes any OSM file format (according to suffix)
```py
.add_node()
.add_way()
.add_relation()
```
- takes osmium objects
- or Python objects with the same attributes
---
# Example: Filter all highways
```py
writer = osmium.SimpleWriter("highways.osm.xml")
class HighwayFilter(osmium.SimpleHandler):
def way(self, w):
if 'highway' in w.tags:
writer.add_way(w)
HighwayFilter().apply_file("switzerland.osm.pbf")
```
---
# Example: Filter all highways (2nd try)
```py
highway_nodes = set()
class NodesCollect(osmium.SimpleHandler):
def way(self, w):
if 'highway' in w.tags:
highway_nodes.update([n.ref for n in w.nodes])
NodesCollect.apply_file("switzerland.osm.pbf")
writer = osmium.SimpleWriter("highways.osm.xml")
class HighwayFilter(osmium.SimpleHandler):
def way(self, w):
if 'highway' in w.tags:
self.writer.add_way(w)
def node(self, n):
if node.id in highway_nodes:
writer.add_node(n)
HighwayFilter.apply_file("switzerland.osm.pbf")
```
---
# Example: Filter all highways (3rd try)
```py
highway_nodes = set()
class NodesCollect(osmium.SimpleHandler):
def way(self, w):
if 'highway' in w.tags:
highway_nodes.update([n.ref for n in w.nodes])
NodesCollect.apply_file("switzerland.osm.pbf")
writer = osmium.SimpleWriter("highways.osm.xml")
class HighwayFilter(osmium.SimpleHandler):
def way(self, w):
if 'highway' in w.tags:
self.writer.add_way(w)
def node(self, n):
if node.id in highway_nodes:
writer.add_node(n.replace(tags={}))
HighwayFilter.apply_file("switzerland.osm.pbf")
```
---
# Advanced Topics
- converting your own data to OSM format
- relation member handling
- location caches
- OSM data diff download and processing
- OSM history files
- OSM metadata
# Future
- extend support for Windows
- special handlers (e.g. prefiltering)
- advanced osmium functions (e.g. area builder)
---
class: middle, center
# pip install osmium
**Documentation**: http://docs.osmcode.org/pyosmium/latest/
**Source code**: https://github.com/osmcode/pyosmium
**Slides**: https://github.com/lonvia/geopython17-pyosmium
**email**: `lonvia@denofr.de`
</textarea>
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