[Openstreetmap] Introduction

[Matt Amos]

On Tuesday 05 October 2004 12:12, SteveC wrote:
> * Jono Bacon (jono at jonobacon.org) wrote:
> > <snip>
> >
> > This sounds like an interesting idea, and a little different to
> > how I initially envisaged community based mapping.

there have been some good ideas out there about this sort of thing, 
but steve (tried to) convince me that planter/gardener type schemes 
raise the barrier to entry. something i reckon we all agree on is 
that people with and without GPS units should be able to contribute 
without difficulty (hence the java applet, which i don't like, but 
thats just me)

> > I assume you folks have discussed the relative merits of using
> > the GPS data to automatically plot the map as opposed to using it
> > as a sketch. What do you feel makes the sketching option the
> > better choice?

the main point here is simplicity: if you walk (esp. walking) down 
"straight street" (in imaginaryville) then your track will not be 
straight, and may even cross itself due to noise, or you walking up 
and down to find a shop.

mentally you know that the road is almost perfectly straight, so you 
can use the GPS track as a guide. later, someone with WAAS/DGPS and 
von-kalman filtering can come along and make sure your entry is 
accurate.

> One person can take the map, and others can add road names and
> whatnot. The idea is to seperate (to some extent) the geographical
> and the meta data. For example, I might drive around... Sheffield
> and have a map but no nothing about the street names, or not have
> the time to add them. What I use can add notes to the data (more
> below).

even further, i'd suggest a separation between geographical, 
topological and meta-data. i.e: you have a road comprising its path 
in space (geo), which other roads it connects to (topo) and its name, 
width, M/A/B status and number (meta), etc...

allowing people to edit these separately is (imho) better than lumping 
them all together and having to worry about two identical roads with 
different names or roads which appear to cross but don't, etc...

> > Another option for either methods is to have a selection box in
> > the GPS tool that allows the user to define what kind of surface
> > they are travelling on. As an example, if they are going onto the
> > M6, they would select Motorway. You could define all kinds of
> > types of surface, including, but not limited to roads. You could
> > also include paths, parks, private drives and various other types
> > of information.
>
> Yep!

all of this is meta-data and when i say "road" its just because thats 
the primary focus. it'd be great to have people putting bridleways 
and tube lines (although the data would have to come from somewhere 
else!) and air corridors on openstreetmap!

theres also other kinds of paths (coastlines, administrative 
boundaries) which can probably be dealt with using meta-data.

> > Is it possible to create the map as some kind of vector based
> > unit so that when you zoom in closer, you get more detail of the
> > map? I have no idea how this would be done.
>
> Me neither. IMHO expedia maps doesn't do this brilliantly well, in
> how it chosses what to label at what zoom level.

multimap seems to do this quite well. there are a profusion of vector 
formats which could be used for export (pdf, svg, etc...) but 
addressing an "appropriate level of detail" is A Difficult Problem.

> > - What tool are you using to actually store the GPS sketch before
> > it is uploaded?

we plan to allow people to upload saved tracks from their GPS software 
- we're gonna need help doing this because both steve and i use gpsd, 
which outputs in ASCII format with a column for lat, long, alt and 
time each. (and steve uses his own obfuscated c++ program as well)

cya,

matt

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