per chi non legge la talk...
---------- Forwarded message ---------- From: Mayeul KAUFFMANN <[email protected]> Date: Tue, Jul 19, 2011 at 11:22 Subject: [Imports] EC-JRC built-up areas / proposed process v0.1 To: OSM Imports List <[email protected]> Hi, Thanks all for the fruitful discussion and the helpful comments! We agree on the need for local, manual validation. As a trial, we could start with a 50 by 50 km low density area (something like http://osm.org/go/0CkJV_Q- ) and have it fully validated by the local community, hence only manual edits. The process could be as follows: 1. Extract built-up areas and building density from imagery (automated) 2. For each polygon (semi-automated): 2a. In the area covered by the polygon and in the neighbourood (say 0,5 to 1 km buffer) do an analysis of all tags related to landuse. Continue with next step 2b only if there is absolutely no relevant information in OSM (to avoid duplicates or overlapping polygons). 2b. Have an algorithm choose the best combination of tags for this polygon (without uploading). This could be decided on the basis of 2a (the polygons already coded in 2a are our training set): e.g., among our polygons, let's take those that are very similar to OSM polygons already tagged in OSM as “place=village” (we have dozen of textural, morphological, etc. measures for this); for those, we propose the tag “place=village”. We are thinking of doing some kind of statistical analysis (PCA/supervised classification) here. After this step, we may even go back to step 1 (maybe iteratively) to fine-tune our detection algorithm (the algorithm produces a continuous value, we have to discretize it with a threshold, step 2b can help us choose the threshold that best fit existing OSM data) 2c. For polygons ruled out in step 2a, compute one or two statistics (such as building density, and maybe average building size for instance) for the OSM polygon 3. Share the polygons by USB key or email to other local fellow mappers (no posting to a web site). I have a few names in mind: In the past few weeks, as a hobby, I've been training friends of the Italian Alpine Club (especially the mountain bikers) on OSM mapping, and altogether they have an excellent knowledge of the area. I have also put an announcement in http://wiki.openstreetmap.org/wiki/Lombardia_Community (you will also find my two login names here ;-) ). I also have contacts with several active mappers in other institutes of our research center. 4. Have local mappers (including myself) manually validate or reject each polygon, and manually upload the validated polygons, with appropriate tags (e.g. landuse=residential, landuse=commercial, place=village...) 5. Report on the above. The area that we suggest ( http://osm.org/go/0CkJV_Q- ) seems a good place to test this, as there are already a few village polygons digitized, but many are missing, and the majority of building footprints are missing. Jorge wrote: “But you can contribute by calculating, for example, the OSM building coverage in some countries or cities, and then let the community knows how bad/good is the current OSM coverage.” We like this idea, but how can we share it? (legal and technical constraint). This is strongly related to the next point: The only thing that does not fit in the above 5-step process is how to share the result of step 2c (it is not convenient to share id/density pairs by email). Maybe this could be the (semi-) automatically uploaded part. Thanks in advance for any comment. Mayeul Dr. Mayeul KAUFFMANN, Spatial Data Analyst European Commission, Joint Research Centre (JRC) Geo-Spatial Information Analysis for Global Security and Stability (ISFEREA) Via E. Fermi 2749 - I-21027 Ispra (VA), ITALY http://isferea.jrc.ec.europa.eu _______________________________________________ Imports mailing list [email protected] http://lists.openstreetmap.org/listinfo/imports -- -S _______________________________________________ Talk-it mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-it
