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adapt to 7960be55fe

Dane Springmeyer 2014-06-12 18:30:21 -07:00
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OsmPlugin.md

@ -1,13 +1,13 @@
Mapnik's [[PluginArchitecture]] supports the use of different input formats.
This plugin allows for the direct reading of data from the [OpenStreetMap XML format](http://wiki.openstreetmap.org/wiki/.osm). You can use it in two different ways; you can either render a local file, or connect to a URL which provides OSM XML data within a given bounding box.
This plugin allows for the direct reading of data from the [OpenStreetMap XML format](http://wiki.openstreetmap.org/wiki/.osm).
*NOTE*: the primary way that Mapnik is used to render OpenStreetMap data is to import an [extract](http://wiki.openstreetmap.org/wiki/Planet.osm) into Postgres using the [osm2pgsql](http://wiki.openstreetmap.org/wiki/Osm2pgsql) tool and then read it using [[PostGIS]] plugin.
# Dependencies
You need libxml2 installed on your system for parsing the XML, and libcurl (http://curl.haxx.se) for making connections across the network (this is needed so that the OSM plugin can connect to remote servers to fetch OSM data).
You need libxml2 installed on your system for parsing the XML.
# Parameters
@ -15,7 +15,6 @@ You need libxml2 installed on your system for parsing the XML, and libcurl (http
| *parameter* | *value* | *description* | *default* |
|-------------|----------|---------------|-----------|
| file | string | the OSM file to load | |
| url | string | the URL of an OSM data source (see below). | |
| bbox | string | the bounding box to load from the URL of an OSM data source (see below). | |
| parser | string | the XML parser: currently, this must have a value of "libxml2" as libxml2 is the only parser currently supported | libxml2 |
| filter_factor | double | filter to use when querying for raster data | 0.0 |
@ -43,35 +42,10 @@ For example:
</Layer>
```
## Specifying the data's source
OSM data may be sourced from two different places: a file (as in the example above) or the web. As the example above illustrates, you can specify a source OSM file by specifying a Parameter with a name of "file".
For a web data source, we must provide two parameters: the base URL and the bounding box in WGS84 latitude/longitude. These two parameters are named "url" and "bbox". The full URL of the OSM data server will be constructed from the base URL with the bounding box added as a query string. Here is an example:
```xml
<Layer name="roads" status="on" srs="+proj=latlong +datum=WGS84">
<StyleName>residential</StyleName>
<StyleName>unclassified</StyleName>
<StyleName>secondary</StyleName>
<StyleName>primary</StyleName>
<StyleName>motorway</StyleName>
<Datasource>
<Parameter name="type">osm</Parameter>
<Parameter name="url">http://www.osmdataserver.com/data.php</Parameter>
<Parameter name="bbox">-0.8,51,-0.7,51.1<Parameter>
</Datasource>
</Layer>
```
In the above example, the full URL of the OSM data server would be `http://www.osmdataserver.com/data.php?bbox=-0.8,51,-0.7,51.1`. Data will be downloaded from this URL and rendered according to the rules in the style file.
## Styling the output
Styling the output is done in the same way as for other data sources, with tests for different tags done in the `<Filter>` tag. For example this rule will match OSM ways where the 'highway' tag is equal to 'path' and the 'foot' tag is equal to 'designated':
```xml
<Rule>
<Filter>[highway] = 'path' and [foot] = 'designated'</Filter>
@ -111,41 +85,4 @@ Currently these tag/values are assumed to be polygons:
- landuse=industrial.
These are defined in the polygon_types class in the source file osm.h, so if you want to add others for your own use, that's the place to go.
## Demo programs
There are two demo programs available in the source distribution, "render" and "easymapnik".
### render
The first, render.cpp, is a very simple application which will render a given OSM file according to the rules in a given Mapnik XML file. The usage is:
`render MapnikXML w s e n [OSMfile]`
w, s, e and n represent the bounding box to zoom to. By default you specify the source OSM file in the Mapnik XML file; however, you may also supply it as an optional sixth parameter.
### easymapnik
easymapnik is the beginnings of a project to develop an application to allow easy rendering of OSM data from file or from an OSM data server, without the need to install a PostGIS database, or, ultimately, to write a Mapnik rules file. At the moment it's very much a demo app, rather than a production-ready app, but nonetheless it demonstrates how you can render OSM data from an OSM data source or server. It's available in the "demo" directory and has a Makefile which has so far only been tested on OS X 10.5 with a version of Mapnik dating from early 2009. The usage is:
```
`easymapnik -s source [-w width] [-h height] -x xmlfile [-i InOSMFile] [-o OutPNGFile] [-t] [-z startzoom] [-Z endzoom] [-b bbox] [-u serverURL] [-m]`
To go through each option one at a time:
-s : specify the source, this maybe either 'osm' or 'api'. The former reads from an OSM file; the latter, from a server.
-h : height of output image.
-x : Mapnik XML file; you must currently write this by hand! However it need not specify an OSM file or URL.
-i : input OSM file; only applies with '-s osm'.
-o : output PNG file.
-t : use tiled output mode, which generates Google-style x,y,z tiles. You must specify the -z and -Z
options for this.
-z : start zoom for tiled output (see above)
-Z : end zoom for tiled output (see above)
-b : bounding box for OSM data URL; only applies with '-s api'.
-u : server URL; only applies with '-s api'.
-m : multirequest mode; if you're requesting a relatively large area from the server, the data will
be fetched in 0.1x0.1 degree tiles.
```