Re: [OSM-Talk-ZA] Cleaning up an old import
On 10 February 2013 09:05, David Schneider d.schnei...@tradermail.info wrote: Hi List! I searched an address in the eastern parts of Cape Town, and I was suprised that nomatim didn't report it as residential. I checked the data, and found that vast parts of Cape Town's residential areas are made up from unclassified roads instead of residential! From the metadata, this seems to be the result of an import some years ago. Yes, the City of Cape Town (CoCT) municipality gave us road data a number of years ago. The data wasn't brilliant and did not make a distinction between residential roads and unclassified. We used the data to fill areas that hadn't been mapped. Mitchell's Plain, Rocklands, Khayelitsha, Eesterivier etc. The data was cleaned up (to a degree: over nodeing, connectivity, over slitting, etc) and added by myself (Firefishy), Adrian Frith and I think Ryan Peel. We were initially planning to use the http://osm.org/user/City%20of%20Cape%20Town%20Import I feel this should be fixed. I don't know if this can be done auto- matically, or a manual community effort is required. My proposal would be to select user=Firefishy maxspeed=60 highway=unclassified in JOSM and change all to residential. Now, a few roads that should be unclassified will be residential, but the ratio seems to be 99% wrong now vs. 1% wrong after this change. Of course, roads that have been touched since the import will missed by this, but there will be an improvement for sure. WAIT! Please do not select and mass change. Better to do the changes based on aerial imagery and local knowledge. It would be great to fix up the data. As detailed above I was not the only person to have add the CoCT data. Another thing that I noticed is that the roads are massively over-noded. http://www.openstreetmap.org/browse/way/32216567 demonstrates both. It should be residential, and if you compare to aerial images, the straight section is represented with 6 nodes, 3 of them within 5m. I presume this comes from calculating the centerline of a full shape, as the road widens towards the east, where the many nodes are. (I would map that road with 3 nodes, with the two on the eastern sides interfacing between the NW-SE road, going away at 90° from there. I.e. making a slight right turn when going east. The data is just the opposite, going to the left, which gives an odd angle that is not there in reality when you come from the south and turn east.) JOSM has a built-in simply function, select way and press Shift-Y. Do not be too trigger happy with simplifying, especially if a mapper has spent time to create good natural curves. One of the annoying artifacts from the CoCT data is at T junctions there are often pointless nodes very close to the junctions, these should be removed or moved as they can disrupt mapping. Regards Grant (aka Firefishy) ___ Talk-ZA mailing list Talk-ZA@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-za
[OSM-Talk-ZA] Cleaning up an old import
Hi List! I searched an address in the eastern parts of Cape Town, and I was suprised that nomatim didn't report it as residential. I checked the data, and found that vast parts of Cape Town's residential areas are made up from unclassified roads instead of residential! From the metadata, this seems to be the result of an import some years ago. I feel this should be fixed. I don't know if this can be done auto- matically, or a manual community effort is required. My proposal would be to select user=Firefishy maxspeed=60 highway=unclassified in JOSM and change all to residential. Now, a few roads that should be unclassified will be residential, but the ratio seems to be 99% wrong now vs. 1% wrong after this change. Of course, roads that have been touched since the import will missed by this, but there will be an improvement for sure. Another thing that I noticed is that the roads are massively over-noded. http://www.openstreetmap.org/browse/way/32216567 demonstrates both. It should be residential, and if you compare to aerial images, the straight section is represented with 6 nodes, 3 of them within 5m. I presume this comes from calculating the centerline of a full shape, as the road widens towards the east, where the many nodes are. (I would map that road with 3 nodes, with the two on the eastern sides interfacing between the NW-SE road, going away at 90° from there. I.e. making a slight right turn when going east. The data is just the opposite, going to the left, which gives an odd angle that is not there in reality when you come from the south and turn east.) I downloaded a section of Cape Town, exported to GPX and used gpsbabel to apply the Douglas-Pecker algorithm with 1m max deviation. The number of nodes went down to less than half! So maybe removing some excess nodes could be performed during any update. Best, David ___ Talk-ZA mailing list Talk-ZA@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-za
Re: [OSM-Talk-ZA] Cleaning up an old import
This is an excellent idea. I didn't even notice this. THe bandwidth and storage perks of doing this across large areas could be tremendous. I hope this can be done, I would not have even suggested this in fear of it going nowhere. Think I am going to start looking for similiar problems in my vicinity. Regards Marlon On Sun, Feb 10, 2013 at 11:05 AM, David Schneider d.schnei...@tradermail.info wrote: Hi List! I searched an address in the eastern parts of Cape Town, and I was suprised that nomatim didn't report it as residential. I checked the data, and found that vast parts of Cape Town's residential areas are made up from unclassified roads instead of residential! From the metadata, this seems to be the result of an import some years ago. I feel this should be fixed. I don't know if this can be done auto- matically, or a manual community effort is required. My proposal would be to select user=Firefishy maxspeed=60 highway=unclassified in JOSM and change all to residential. Now, a few roads that should be unclassified will be residential, but the ratio seems to be 99% wrong now vs. 1% wrong after this change. Of course, roads that have been touched since the import will missed by this, but there will be an improvement for sure. Another thing that I noticed is that the roads are massively over-noded. http://www.openstreetmap.org/browse/way/32216567 demonstrates both. It should be residential, and if you compare to aerial images, the straight section is represented with 6 nodes, 3 of them within 5m. I presume this comes from calculating the centerline of a full shape, as the road widens towards the east, where the many nodes are. (I would map that road with 3 nodes, with the two on the eastern sides interfacing between the NW-SE road, going away at 90° from there. I.e. making a slight right turn when going east. The data is just the opposite, going to the left, which gives an odd angle that is not there in reality when you come from the south and turn east.) I downloaded a section of Cape Town, exported to GPX and used gpsbabel to apply the Douglas-Pecker algorithm with 1m max deviation. The number of nodes went down to less than half! So maybe removing some excess nodes could be performed during any update. Best, David ___ Talk-ZA mailing list Talk-ZA@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-za ___ Talk-ZA mailing list Talk-ZA@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-za
Re: [OSM-Talk-ZA] Cleaning up an old import
Hi I would suggest downloading the section in JOSM if you don't already use it. You can then very easily apply a filter and then select all the objects and apply/change a preset where required. I would also suggested contacting the contributor privately first before mailing to public forums. There might have been a good reason for the classification and other issues you mentioned. Regards On 10 February 2013 09:05, David Schneider d.schnei...@tradermail.infowrote: Hi List! I searched an address in the eastern parts of Cape Town, and I was suprised that nomatim didn't report it as residential. I checked the data, and found that vast parts of Cape Town's residential areas are made up from unclassified roads instead of residential! From the metadata, this seems to be the result of an import some years ago. I feel this should be fixed. I don't know if this can be done auto- matically, or a manual community effort is required. My proposal would be to select user=Firefishy maxspeed=60 highway=unclassified in JOSM and change all to residential. Now, a few roads that should be unclassified will be residential, but the ratio seems to be 99% wrong now vs. 1% wrong after this change. Of course, roads that have been touched since the import will missed by this, but there will be an improvement for sure. Another thing that I noticed is that the roads are massively over-noded. http://www.openstreetmap.org/browse/way/32216567 demonstrates both. It should be residential, and if you compare to aerial images, the straight section is represented with 6 nodes, 3 of them within 5m. I presume this comes from calculating the centerline of a full shape, as the road widens towards the east, where the many nodes are. (I would map that road with 3 nodes, with the two on the eastern sides interfacing between the NW-SE road, going away at 90° from there. I.e. making a slight right turn when going east. The data is just the opposite, going to the left, which gives an odd angle that is not there in reality when you come from the south and turn east.) I downloaded a section of Cape Town, exported to GPX and used gpsbabel to apply the Douglas-Pecker algorithm with 1m max deviation. The number of nodes went down to less than half! So maybe removing some excess nodes could be performed during any update. Best, David ___ Talk-ZA mailing list Talk-ZA@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-za -- Gerhardus Geldenhuis ___ Talk-ZA mailing list Talk-ZA@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-za
