[OSM-talk] [OSM-dev] Developers requested to help provide "completeness" tools

Chris Morley c.morley at dsl.pipex.com
Mon May 12 17:06:59 BST 2008


David Earl wrote:
> Here is what I was going to do:
> 
> 1. use a set of ways like coastline (i.e. with an "on the right" rule, 
> because they'd be too long as one way), to define areas of completeness. 
> By definition, coastline would form one boundary.
> 
> 2. Render these plus coastline to a new set of tiles (possibly only at 
> one zoom level, say 13 or 14) so that complete areas are transparent and 
> incomplete areas are semi transparent red, say. Use the ocean tiles 
> database to avoid putting red over all areas of sea.
> 
> 3. Present these tiles as a layer. For other zooms either combine or 
> divide, or sample, or simply rescale in the browser - the edges need 
> only be quite coarse.
> 
> I felt this leveraged most from the tools we already have so would be 
> the most straightforward to implement.
> 
> I was going to have only one measure of "complete", that is the surveyor 
> asserts that all publicly-accessible roads are present, with names for 
> all except for those impossible to determine and when that is indicated, 
> and all key points of interest from a limited set: schools, pubs, places 
> of worship; and any railways and significant watercourses.
> 
> I think it would be confusing for a consumer to have lots of variations 
> in what "complete" means - just an indicator to say "you can't really 
> trust this area yet" would be simple.
> 
> However, since the boundaries can be tagged, there would not be any 
> problem about expanding this for internal use to cover degrees of 
> completeness.

I think this is the right approach. I prefer the completeness boundary 
being a tagged way over the predefined squares approach suggested by 
Andy because:

a) Being able to expand the boundary after each session is likely to be 
a great motivator. I suspect that this progressive "taming of the 
wilderness" or "making order out of the void" is what drives many mappers.

b) Applicability to small or irregular areas (route to work?) might 
encourage more users.

c) No additional tools or procedures are need by the mapper.

Starting with a single level of completeness makes sense, but I think it 
should be public roads, named where feasible. This covers the essential 
basic requirements for a number of potential applications for example, 
routing, delivery, estate agents, bus services. The points of interest, 
etc. are clearly desirable and but may not be always collected. For 
instance, tracing from arial photos and naming from an out of copyright 
gazeteer; or imports like TIGER. (Also I'm not sure I collected all of 
them when I started 2 years ago.) Start basic and have these in a 
subsequent level.

Chris




More information about the talk mailing list