[OSM-talk] Cartography meetup

David Earl david at frankieandshadow.com
Tue Feb 6 17:25:11 GMT 2007


I'd quite like to come to this if the day and transport works. I had a very
sleepless night a month or so ago so instead of sleeping got up and wrote
down the basis for a series of algorithms I would use if I was starting a
map renderer from scratch, some of which might be useful.

Though useful up to now, I'm doubtful that osmarender has a future. I don't
think the rules based approach is nearly flexible enough. Presumably that's
mapnik was started. Osmarender is prettier than mapnik at the moment, but I
assume that's simply because mapnik doesn't understand lots of different
kinds of area at present, and this is just donkeywork to fix; similarly many
areas look like ways.

Six things that would be on the top of my priority list (bear in mind I'm
not familiar with current developments except those I can see, so some of
this may be done or in progress):

- In Mapnik all crossing ways look like they join, even if they are in
separate layers, or indeed areas roads crossing boundaries of certain areas.
This is highly misleading. I suspect this is pretty fundamental part of the
algorithm. (e.g. consider
http://labs.metacarta.com/osm/?lat=6805146.94826&lon=24024.15307&zoom=16&lay
ers=B0 - the border of the roads on the roundabout doesn't cross the
underlying roads (which are in a lower layer), but links up with them, and a
little bit further to the west at
http://labs.metacarta.com/osm/?lat=6805146.94826&lon=23241.27086&zoom=16&lay
ers=B0 the trunk edging is broken by the cycleway which actually goes under
the road, but looks like it crosses it at grade. (Explicit bridge rendering
would help, but even so if two ways do not connect at a node, they should
not appear to connect on the map).

- Improvement to the online presentation.
 + People I have referred to the website frequently tell me they find it
hard to find the map;
 + tiles frequently show up as "more osm coming soon" even though they are
and sometimes will appear a second or third time of trying;
 + the ability to offer a URL direct to a particular portion/zoom level of
the map, as per Permalink on http://labs.metacarta.com/osm;
 + better support for Internet Explorer (like it or not, it is far and away
the most common browser).
 + tick boxes or whatever to include or limit the information displayed
under user control rather than just by scale.

- overlapping captions (both text interfering with other text and areas
overlaying text, e.g. "Vue Cinema (mult"... vs "Grafton"..., and to the east
names of buildings at
http://labs.metacarta.com/osm/?lat=6803649.26057&lon=15061.31628&zoom=16&lay
ers=B0 ), and missing captions (some roads are so short that their names
never appear (Mapnik) or are clipped (osmarender), e.g. the little spur of
Ross Street at the centre of
http://labs.metacarta.com/osm/?lat=6802665.13404&lon=16615.73457&zoom=16&lay
ers=B0 has a name). An algorithm to handle this properly is complex, but
there could be an easy win if renderers were to take notice of newlines in
node captions, to allow a more compact rendering (especially in osmarender,
the long strings going off to the right). A more automated approach would
e.g. be to try to get captions into as square a box as possible using word
breaks to wrap - some node and area captions seem to do this or something
similar already, but not all.

- missing symbols as others have said, but also directional icons
(principally one way street arrows) and names of things where only an icon
is currently shown (e.g. pub names in Mapnik). The latter is pretty trivial,
but a more advanced version would compare areas and nodes for common names
and render only the name on the node if so (otherwise it appears twice;
obviously a renderer that does these names correctly would mitigate against
node+area in future, but at present that's not the case). Contours as
standard.

(nb I did SVG's for quite a large additional set of things in the osmarender
control file I pointed at a couple of weeks back. I will try to make an
effort to upload these to the SVG icons page shortly.

- Reliability indicator. This is a data issue as well as a presentational
one. At the moment I cannot tell by looking how reliable an area is. If I
can't judge the maps trustworthiness, am I really going to use it? For
example, red and yellow backgrounds or stripes for areas which are minimally
or partially mapped. This also helps contributors know where their efforts
might be best directed. Obviously this information can lie or there may be
errors, but in most cases, we contributors know which areas have work to do
and those which we consider complete, to some definition of "complete"and
could indicate this.

- Better online name search capability
(http://trac.openstreetmap.org/ticket/281). I've since thought more about
how I could make such a search efficient.

David

> -----Original Message-----
> From: talk-bounces at openstreetmap.org
> [mailto:talk-bounces at openstreetmap.org]On Behalf Of Andy Robinson
> Sent: 06 February 2007 09:12
> To: 'Nick Whitelegg'; 'SteveC'
> Cc: talk at openstreetmap.org; 'Richard Fairhurst'; 'Steve Chilton'
> Subject: Re: [OSM-talk] Cartography meetup
>
>
> ...and if the day were to fit then I'd probably join in to
> interface on the
> tagging side.
>
> Cheers
>
> Andy
>
> Andy Robinson
> Andy_J_Robinson at blueyonder.co.uk
>
> >-----Original Message-----
> >From: talk-bounces at openstreetmap.org [mailto:talk-
> >bounces at openstreetmap.org] On Behalf Of Nick Whitelegg
> >Sent: 06 February 2007 8:18 AM
> >To: SteveC
> >Cc: talk at openstreetmap.org; Richard Fairhurst; Steve Chilton
> >Subject: Re: [OSM-talk] Cartography meetup
> >
> >>I think it would be neat for the people who defined the map styles, the
> >>people who run the tile render machinery, and some Real Cartographers to
> >>sit down and improve the cartography of our maps.
> >
> >>Lots has been done, but I think there's some room for improvement.
> >
> >>I would suggest that we meet (in Oxford?) for a day. I think if we
> >>structure a day around each zoom level and what to show and how to show
> >>it we could achieve some kick-ass cartography.
> >
> >Sounds good - as I do rendering with Freemap, I would be interested in
> >this. Incidentally is there any scope for the Freemap maps being
> >integrated into the main OSM viewer, perhaps as an option? I say as an
> >option as I use OSGB projection, as it makes a number of things a lot
> >easier.
> >
> >Nick
> >
> >
> >
> >_______________________________________________
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> >talk at openstreetmap.org
> >http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
>
>
>
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