Thanks Kate! 22 apr 2012 kl. 15:19 skrev Kate Chapman:
> Hi Martin, > > It is the same exact satellite shot between the Bing and the Digital > Globe Imagery that HOT bought. If you go look at cars on > intersections they are in the same place. Ah, you're right. I've been doing some more checking and what got me confused was that surrounding the area I'm working on I see buildings that are tagged with source=digitalglobe, but that align a lot worse with the Digital Globe Imagery than with Bing. I guess these areas need to be fixed then, as the source-tagging and alignment don't match. So, here's a plan for getting it right: - Add the Digital Globe imagery (guess it will be necessary after all) in Potlatch. - Once a task has been selected, adjust the Bing imagery (using space+drag in Potlatch) to align it with the Digital Globe images at zoom level 18. - Do tracing with the, now aligned, Bing imagery at zoom level 19 (where Digital Globe is not available). - As the offset is based on Digital Globe, tag the traced material with "source=digitalglobe". Holler if I'm not thinking right. KR, Martin > I would suggest adjusting the Bing imagery offset if you are going to > use it, since most of the rest of the tracing happened long before > high resolution imagery was available of Padang through Bing. We > won't have any idea of knowing which is right until there are GPS > tracks of the area, I don't see that happening anytime very soon. > > If adjusting the offset is too complicated then please use the Digital > Globe Imagery so it matches up with everything else. > > Thanks, > > -Kate > > On Sun, Apr 22, 2012 at 6:36 AM, Martin Holmgren <[email protected]> wrote: >> Hi all! >> >> On May 9th I'll be giving a short introduction to OSM, HOT and mapping using >> Potlatch 2 to a group of mostly GIS and IT professionals here in West >> Sweden. My idea is to have the participants take tasks in Padang using the >> tasking manager and do some tracing of buildings. To me it seems like a >> perfect introduction both to OSM and HOT as tracing and tagging buildings >> requires a minimum of knowledge about tagging schemes (basically >> "building=yes, source=...") and the more complex aspects of the data model. >> >> In my own mapping I have used both the Digital Globe imagery and Bing >> Aerials, where I have tried to offset Bing to match the previous traces with >> Digital Globe as source. Now, reading the (about two months old) discussion >> below, I guess I rather should have either >> >> a) according to Jaakko's view: kept Bing in its original position and used >> the source tag to allow for adjustment at a later stage, when we have >> background material that is more consistent or >> b) avoided using Bing altogether, based on Kate's suggestion. >> >> Even if b) would give a more consistent map, I see a couple of problems, >> both in general and pertaining to my planned mapping activity: >> >> - the Bing (as opposed to the Digital Globe) imagery is available also on >> zoom level 19, which makes it considerably easier to do tracing. >> - manually adding the Digital Globe images is an extra barrier to getting >> going. (ok, in the case of our mapping activity it could be managed, since >> they will all be computer savvy) >> - with Bing imagery available directly in Potlatch there is a risk that >> people who either don't use the task manager, or who miss reading the >> instructions, do tracing using Bing unknowing of the Digital Globe material. >> >> My question is therefore: is it ok for us to trace using Bing (tagged >> "source=Bing Aerial") with no offset, or should we still take the extra step >> of configuring the Digital Globe imagery in Potlatch? >> >> I'd love to get this as right as possible before having a group of people do >> a lot of tracing, so any suggestions on what approach to take are very >> welcome! >> >> Kind regards, Martin >> >> 13 feb 2012 kl. 21:26 skrev Jaakko Helleranta.com: >> >>> This is (one of the) reason(s) I think ppl should use source tag (possibly >>> source:geometry) on all mapped objects. .. Makes adjusting easier as one >>> can filter with the tag when traces or other more solid information on >>> imagery accuracy becomes available. >>> >>> Cheers, >>> -Jaakko >>> >>> Ps. Talking of traces, imagery, and accuracy I think it would be good to >>> try to figure out how to partner with various development / humanitarian >>> players (and why not private sector players / "even" governments to create >>> a "reference trace set" for any area in which we are active in. >>> I'm trying to figure that out here in Haiti as implied in my msg a few hrs >>> ago. >>> Has some tried to do this somewhere else? .. I remember reading somewhere >>> that something along these lines was (one of) the base data set(s) for OSM >>> in London in the beginning of the whole OSM project. >>> >>> ------Original Message------ >>> From: Kate Chapman >>> To: HOT@OSM (Humanitarian OpenStreetMap Team) >>> Subject: [HOT] Padang Mapping Task >>> Sent: Feb 13, 2012 14:27 >>> >>> Hey All, >>> >>> Just wanted to make you aware there is an offset between the imagery >>> available in Bing and the imagery we've been using. >>> >>> I think the best thing to do right now is to continue using the >>> imagery we were using. Eventually when there is more GPS traces >>> available we might be able to correct. At the moment though there >>> isn't a good way of knowing which is best. >>> >>> Also if you run across some buildings that are offset I think it is >>> best to line them up with the imagery so it is consistent. If someone >>> has a better suggestion let me know. >>> >>> http://tasks.hotosm.org/job/9 >>> >>> Thanks! >>> >>> -Kate >>> >>> _______________________________________________ >>> HOT mailing list >>> [email protected] >>> http://lists.openstreetmap.org/listinfo/hot >>> >>> >>> Sent from my BlackBerry® device from Digicel >>> -- >>> Mobile: +509-37-26 91 54, Skype/GoogleTalk: jhelleranta >>> _______________________________________________ >>> HOT mailing list >>> [email protected] >>> http://lists.openstreetmap.org/listinfo/hot >> >> >> _______________________________________________ >> HOT mailing list >> [email protected] >> http://lists.openstreetmap.org/listinfo/hot _______________________________________________ HOT mailing list [email protected] http://lists.openstreetmap.org/listinfo/hot
