Elevation

Another long time without mentioning any advancements on my map making efforts. While not much has changed, what has changed is a big step to easier customization.

In the last post in this series I gave a quick list on how I make my own maps:

• Use SRTM elevation to generate a hypsometric base map, hill and slope shading, and finally hypsometric curves. For the latter I'm using gdal-contour and shp2pgsql.
• Use any extract you want and import them with osm2pgsql. Small extracts import quite quick, but so far, I have never succeeded to import a big part of Europe (from Portugal to south Finland, so it covers UK/Ireland and Istambul) in a machine with 8GiB of RAM and hard disks. The recommendation is to use a machine with lots of RAM (16+, I heard up to 256 for the whole planet) and SSDs.
• Use TileMill for the initial design.
• Do a lot of xml manipulation to try to customize OSM's mapnik style based on your design.
• Use generate_tiles.py to, well, generate the tiles.

But since August 2013 things have changed in the 3rd and 4th items in that list. Andy Allan had finished a first big iteration of redoing OSM's mapnik style in CartoCSS. The latter is a CSS-like language that is the native way to style things in TileMill. Since then, customizing is way much easier, not only because of the Cascading part of CSS, but also because Andy took the time to make a lot of things (widths, colors) to things similar to C/C++'s #defines, which you can override and impact anywhere where the definition is used.

So now, steps 3 and 4 are more like:

• Use TileMill to change OSM's initial design¹.
• Export the design to a mapnik XML file.

In fact, that last step could be avoided, given that TileMill can also render everything by himself.

The last step in having your own tiles to be able to use them. I use Marble in my phone, but I also setup a slippy map so I can brag about it. Unluckily I can't embed the map here (I should fix this).

The tiles served actually come from different rendering passes using different, incremental designs. The previous-to-last one can be seen in Deutschland's region; I will be rendering some parts of London with a newer design before the end of the month.