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 _______________________________________________ HOT mailing list [email protected] http://lists.openstreetmap.org/listinfo/hot
