[HOT] Fwd: Re: New Job for Tracing in the Congo

[Andrew Buck]

Although we don't have population estimates, town area is a pretty
decent proxy for this.  We have discussed this a bit in Mali.  I think
using a numbers based approach like this is the wrong way to go
however.  If someone wants to know how many people a given road
"connects" they can just derive that themselves, just as easily as we
can.  I think the much better thing to put in the DB for developing
countries is a list of tags of things we can determine from imagery
that are not easily computed with GIS software.  This is things like
surface=paved/unpaved, width=* (which can be measured from the
imagery), lanes=* (which can sometimes be determined from the imagery
if the road is paved, or can be guessed based on the measured width,
not sure if we should record the guess as a tag though).  Things like
smoothness and track quality are less reliable from imagery and I
think we should stay away from these, but other things can be recorded
such as river crossing methods (bridge, ford, etc).  The information
from these kinds of tags is much more useful to routers and map
renderers than something the highway=* classification which tends to
get all the focus.  If these tags were properly filled out for the
roads in an area, the actual highway=* tag would just be incidental as
all the more relevant information is explicitely defined, rather than
just guessing based on the classification.

I think the best way to proceed would be to make up a list of tags we
should try to fill in from imagery as well as a "workflow" on how to
fill them out.  It should have instructions for good ways of measuring
widths, where to start/end the width mesaurement, tips for determining
paved/unpaved, etc.  Also included in this document should be things
to aid in the systematic addition of this information, like how to use
the search tool and/or the todo list in josm to make the task
efficient.  Finally it would be good to come up with custom josm paint
styles to facilitate this.

I have already published one such paint style, the "Surface Data
Entry" style is available in the josm prefs menu.  It draws roads with
colors indicating paved/unpaved and also draws them as double lines
down the edges of the road, rather than on the road centerline.  This
prevents the data layer from obstructing your view of the road.

If people are interested in this we should start something like a
shared google document to start writing such a thing and then put it
on the wiki after it is somewhat stabilised.  I would also suggest
getting a group of people working on it together and talking via skype
voice chat while editing the document.  Pierre Béland and I did such a
collaboration writing the Mali Mapping Facts document and it worked
very well.

I am available anytime to work on such a document if others are
interested in joining me.

-AndrewBuck