Hi list, I just _knew_ it would happen. As soon as I would start the Geobase import, some user would step up, and start adding data to the areas I'm about to import. And this is exactly what happened. To my surprise I discovered a whole lot of data southeast of Quebec City, in the Chaudière-Appalaches region: [1]. These are the NTS tiles 021L09, 10, 15, and 16.
At first I was happy that there was some considerable activity in the Quebec region, other than my own. After examining the data, it comes from a user (Robert66) who has only joined us on Monday. Unfortunately this shines through his data as well: most of his roads are not connected, so that would involve a lot of cleanup. Apparently he had a blast this week: many small towns and villages were added. The data even has street names! See for example Montmagny: [2]. So, I've contacted him yesterday, in order to ask for more information. I haven't received a reply yet, but one day isn't that much. Because this area was on my todo list, I decided to continue with my import. Tile 021L10 ([3]) is on tonight's program. After the data was loaded, I noticed a concentration of roads in St. Damien [4], which I didn't see yesterday. Apparently Robert66 was busy adding it today, see changeset 2451637. When zooming in, I noticed that, while the data looked topologically correct (apart from the fact that the roads aren't connected), many roads are displaced, up to 150 m, compared to the Geobase data. See [5], screenshot of OpenJump. Brown=OSM, green=Geobase. I know that Geobase isn't the most accurate dataset, but in the area I have imported data, it generally matched my roads reasonably well. The differences are up to 30 meters, although there are some exceptions. An example is the main road in the St. Damien screenshot, going from SW to NE. It was originally added by me, nearly a year ago: [6], as well as a few residential roads. What I would like to know is: does anyone of you have a reasonable explanation as to how Robert66 has added his data? He has used Potlatch, and for that area there are no detailed Yahoo images. There is only one GPS trace of the main road. (It isn't mine: I'm using them only as a backdrop in JOSM.) I really hope he hasn't drawn the roads from memory, or some sketches, without the help of any GPS. Although I have traced only a few roads in St. Damien, I find it pretty odd that the roads I added myself are matching Geobase well, but the roads added by Robert66, are off up to 150 m! My hands are actually itching to override his data, and only reuse the names, but that isn't really in the spirit of the import. I also don't think that would be wise, because there is no clarity about how he got the data. I think I'll go visit St. Damien this weekend, and do my own survey. If I find out that Robert66's additions are indeed way off as the OpenJump screenshot implies, then I'll probably replace his roads. I'll wait for an answer from him first. Maybe he can use a bit of education :) As for my import, when I was writing this e-mail, I've uploaded the data from the standalone file, with bridges copied over, and some small corrections. See changeset 2452632. I've left out the residential roads in St. Damien. (Sam: there is even a note in your spreadsheet :) ) I'll cleanup the data, except for the St. Damien area. I'll follow a similar procedure for the rest of this entire area. Depending on the answer Robert66 can give me, I'll either leave his data in place, or add more Geobase roads, or eventually I'll survey those towns myself (which will be a lot of work). So, what do you think? Do you have any additional suggestions as how to handle this situation? Regards, Frank [1] http://www.openstreetmap.org/index.html?minlat=46.5&minlon=-71&maxlat=47&maxlon=-70&box=yes&layers=B000FTF [2] http://osm.org/go/cKbzIEER-- [3] http://www.openstreetmap.org/index.html?mlat=46.625&mlon=-70.75&minlat=46.5&minlon=-71&maxlat=46.75&maxlon=-70.5&box=yes&layers=B000FTF [4] http://osm.org/go/cKawVZPY-- [5] http://www.steggink.org/temp/St_Damien_QC.png [6] http://www.openstreetmap.org/browse/way/27080076/history _______________________________________________ Talk-ca mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-ca
