Phil's TopOSM Variant

This is my (Phil Gold's) repository for rendering OpenStreetMap data. It's based on Lars Ahlzen's TopOSM, but I've modified it significantly according to what I want to see in a map.

This repository contains the map stylesheets as well as the core programs for rendering and continuously rerendering a minutely-updated OSM database.

Requirements

I use a pretty standard OSM rendering stack:

• PostgreSQL and PostGIS to store the data
• osm2pgsql to import the data
• osmosis to extract data for North America, plus follow minutely updates
• GDAL and ImageMagick to process elevation data
• Mapnik to render the maps
• OSM "external data", principally the ocean shapefiles

In addition, I use some less common things:

• osm-shields for specialized route shield images
• RabbitMQ (any AMQP server would do) to coordinate the rendering queues
• InfluxDB to record rendering statistics

And my full rendering stack needs stuff from two other repositories:

• Mapnik minutely updates (not yet uploaded anywhere)
• Elevation data and processing pipeline (not yet uploaded anywhere)

Pretty much everything is written in Python. The following modules are used:

• PyPDF2
• amqplib
• boto
• cairo
• dateutil
• filelock
• influxdb
• mapnik
• pika
• xattr

Fonts

I use Besley* and Lato for the map labels. If those aren't available, rendering will fall back to Georgia and Trebuchet MS, which (1) should be available pretty broadly, and (2) are what the USGS currently uses for their topo maps. If those aren't available, either, the rendering will fall back to DejaVu Serif and DejaVu Sans, which are bundled with Mapnik and will always be available.

The low-zoom rendering uses Roadgeek 2014 for interstate shields and will fall back to DejaVu Sans if it's not available.

As a side note, for those interested in a classic USGS topo look: The USGS began using Georgia and Trebuchet MS on their maps in 2011. They also use Arial for a fair bit of typography on the map "collar", or the area on the paper surrounding the map itself. Prior to 2011, the USGS used ITC Souvenir and Univers for its map labels. Also of interest might be BellTopo Sans, an attempt to recreate a typeface found on very old USGS topo maps.

Installation

TBD

File Structure

Configuration

set-toposm-env.templ should be copied to set-toposm-env and edited with appropriate local configuration values.

Before using any of the programs here, either source set-toposm-env, e.g.:

. ./set-toposm-env

Or use the with-toposm-env wrapper:

./with-toposm-env queue_stats.py

Map Stylesheets

The stylesheets are in the carto directory and use CartoCSS. They use images in the symbols and custom-symbols directories.

There's a Makefile for updating the Mapnik stylesheets, so you can just run make after editing any of the CartoCSS files.

Rendering Programs

The heart of the tile rendering is queuemaster.py. It listens for tile requests and expirations (more on those shortly) and issues commands to the rendering daemons to direct rendering of particular tiles.

Tiles are requested by tp.py. It's intended to run as a CGI program on a web server (via the tp.cgi wrapper, which sets the TopOSM environment for it). As it's called for each tile, it check to see if the tile exists and is up to date. If it is, it serves the tile image. If not (it doesn't exist or it's out of date), tp.py sends a rendering request via AMQP to the queuemaster and waits for a response. It has some logic for waiting different amounts of time in different cases and optionally uploading the tiles to Amazon S3 before serving. (Some of that logic is currently hardcoded and really ought to be more configurable.)

When minutely updates are processed, a program (not part of this repository) sends the expired tile list from osmosis to the queuemaster via AMQP. The queuemaster checks to see which existing tile files are affected by the expiration and: (1) marks them as dirty in the filesystem using extended file attributes; and (2) adds them to its rendering queues.

renderd.py manages the rendering processes. A single renderd.py invocation can create multiple rendering threads, with different dequeuing strategies. I use the following command line on my 24-core, 128GB RAM system:

renderd.py missing:2 by_work_available:6 by_zoom:2 important:4

queue_stats.py requests some statistics from the queuemaster and then prints them out.

expire_tiles.py is theoretically for expiring tiles ad hoc. I don't use it much, though, and it hasn't yet been updated to work on Python 3.

toposm.py contains the meat of the actual map rendering. It can also be run from the command line to render arbitrary images. It uses areas.py, common.py, coords.py, and env.py. Most of the other programs import toposm. (stats.py and tileexpire.py are modules used by various of the above programs.)

Check out the MESSAGE_PROTOCOL.md file for more information about the communications between programs.

Credits

TopOSM was originally created by Lars Ahlzen ([email protected]), with contributions from Ian Dees, Phil Gold, Kevin Kenny, Yves Cainaud, Richard Weait, and others.

License: GPLv2