[Mapcss] pgmapcss version 0.9.0

Stephan Bösch-Plepelits skunk at xover.htu.tuwien.ac.at
Sun Nov 2 09:25:42 UTC 2014

Read this text on the blog:

When I attended SOTM-EU in Karlsruhe this year, I was asked by a member of the
Osmose project, if pgmapcss could be used as tool for quality assurance. JOSM
earlier introduced MapCSS based rules[1] for checking possibly incorrect tags
in OpenStreetMap data. Sure, it was possible with pgmapcss – it just needed a
few adaptions. The main challenges were to rewrite the output to a machine
readable format and to use a different database layout (osm2pgsql does not
import the full database, but only features with certain tags).

[1] https://josm.openstreetmap.de/wiki/Help/Validator/MapCSSTagChecker

Machine readable format
Graphical rendering is not the best possible solution, that’s why having
machine readable output is more reasonable. I introduced a second frontend,
“standalone”: The MapCSS stylesheet is compiled into a python script, which can
then be run from the command line or as CGI script. The script will produce
GeoJSON output.

When testing, this proved to be very powerful, I also implemented a web-based
frontend[2] for pgmapcss using OpenLayer 3.0 as feasibility study.

There’s an example GeoJSON output in the README[3].

[2] https://github.com/plepe/ol4pgm
[3] https://github.com/plepe/pgmapcss/blob/master/README.md

Changes in database backend(s)
As second database backend, the pgsnapshot layout from Osmosis is now
supported.  The main benefit is the completeness of the database, but there are
more advantages (there are disadvantages too), e.g. meta information for the
map features (like who edited the feature last, when was the last change, and
so on). This information is available as pseudo tags: “osm:id”, “osm:user”,
“osm:user_id”, “osm:changeset”, “osm:timestamp”, “osm:version”. There’s even an
option to use multipolygons using osmosis-multipolygon[4].

The standard “osm2pgsql” backend also got an update. Now it does no longer
require the existence of the “tags” column, but rather uses the table columns
if available. It will detect the database layout automatically, but you can
influence behaviour using configuration options. The pseudo tag “osm:id” is now
also set.

pgmapcss now generates improved SQL selects, especially for conditions with
e.g. regular expressions, prefix/suffix matches, …

For more details see the database documentation[5].

[4] https://github.com/plepe/osmosis-multipolygon
[5] https://github.com/plepe/pgmapcss/blob/master/doc/database.md

Additional features

* Localization support. There’s certain support for languages, read the
  corresponding chapter in the README.
* Drastically reduced memory consumption.
* New debugging options, see configuration options[6].

[6] https://github.com/plepe/pgmapcss/blob/master/doc/config_options.md

* The background rendering of OpenStreetBrowser[7] now uses a pgmapcss based

[7] http://openstreetbrowser.org/
[8] https://github.com/plepe/OpenStreetBrowser-basemap

Have fun!
Seid unbequem, seid Sand, nicht Öl im Getriebe der Welt! - Günther Eich
| Stephan Bösch-Plepelits,                                            |
| Technische Universität Wien   -    Studien Informatik & Raumplanung |
| Projects:                                                           |
| > openstreetbrowser.org > couchsurfing.org > tubasis.at > bl.mud.at |
| Contact:                                                            |
| > Mail: skunk at xover.mud.at > Blog: plepe.at                         |
| > Twitter: twitter.com/plepe > Jabber: skunk at jabber.at              |

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