[OSM-dev] Hello World

Frederik Ramm frederik at remote.org
Sat Oct 13 13:41:30 BST 2012


Mike,

On 13.10.2012 00:40, Michal Migurski wrote:
> * Generalized and merged dual carriageways for mid-zoom labels,
> * City label placements for low-to-mid zooms generated with simulated annealing,
> * Route shields based on route relations,
> * Merged transit points.

There's often a tradeoff between making a beautiful map and making a 
current map. I have a feeling that some of the things you mention might 
actually incur quite a lot of processing time.

On OSM we're used to have "current" maps. Our default mapnik map updates 
just minutes after you have made a change. The tile layer guidelines for 
our front page say "Services maintaining minutely updates preferred, but 
periods up to two weeks may be acceptable depending on the content of 
the map."; help.openstreetmap.org is full of "I've made a change why 
doesn't it show" questions.

Most of the current techniques for doing stuff like generalization are 
based on a "give me the full planet file and I'll render it" approach 
and are unsuitable for incremental updates; i.e. you would have to have 
a fat machine that generalizes the planet once every night or something.

It is a very interesting technological challenge to make such algorithms 
capable of handlings diffs - for each derived, generalized object you'd 
have to store a pointer to the source objects, and invalidate the 
generalized object when a change occurs in one of the constituent 
objects. That would then pave the way to have current *and* beautiful 
maps. I haven't managed to solve that yet and it would be great if 
somebody did, but I fear it is not something that can be done quickly.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"



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