Yes, when I looked at it in QGIS the other day I also found an offset. I'm not great with projections so it might be solvable with ease or could be tricky.
As for building shapes, the small section I looked at seemed OK. Not to the standard I aim for when tracing, but better than other mappers tracing standard (building tracing is a tedious task). Personally I think its up to the local community as it's them who will be doing any clean up. Definitely need to keep existing OSM buildings/tags. Rob On 25 Apr 2014 04:30, "Mikel Maron" <[email protected]> wrote: > Hi Msilikale, Rob > > Msilikale, thanks for the initiative of sharing the Dar building footprint > data set (which btw is posted at > https://www.dropbox.com/sh/oe08t8tirw7qtuk/AiOhiUBEN5). It is certainly > comprehensively covering the whole metro region, and beyond, massive! > Actually, can you explain the boundary of data set? Seems like the urban > expanse to the south is suddenly cut. > > I took a look at this data set, compared to what's presently in > OpenStreetMap. Certainly much greater coverage in the government data set. > But many of the buildings in OSM have other valuable tags. Any import > process would want to retain these. > > Additionally, there appears to be a consistent offset in this data set. > I'm not sure if it's an artifact of the reprojection, or in some > misalignment in the georeferencing of the source imagery for this building > data set (I assume it was digitized from imagery); or if there is > misalingment in Bing imagery in Dar (though I suspect not, both Google and > Bing align decently well). > > Looking at the geometries of the building footprints themselves, some look > decently accurate relative to the imagery, but in a great majority of cases > there is not correspondence, in a number of ways. Sometimes an individual > building is broken up into several. Other times, the footprint is partially > correct, but then in other parts wrong. And in other cases, there's clearly > been new construction. This is mostly looking in the Central District. If I > look at some place like Tandale, there seems to be even less correspondence > (to be fair, OSM is not much better here). > > If this data were to be imported, it would need to be looked at very > carefully, piece by piece. It couldn't be done in bulk I think. Could be a > big detailed job. And I wonder, would it end up being more work to try to > get this data set to fit the existing OSM data, and imagery, than simply > organizing to trace buildings directly from imagery. Could even possibly be > an interesting microtasking exercise, ala > http://buildinginspector.nypl.org/ > > In any case, Msilikale, worth reading through the Import guidelines to lay > out some of the other considerations, and good next steps, like documenting > this data set and deliberation in the wiki. > http://wiki.openstreetmap.org/wiki/Import/Guidelines > > Best > Mikel > > * Mikel Maron * +14152835207 @mikel s:mikelmaron > On Monday, April 21, 2014 5:45 PM, Rob Nickerson < > [email protected]> wrote: > > Hi Msilikale, > > Thanks for uploading the Tanzania, Dar es salaam buildings data to > dropbox. I've downloaded it and had a quick look. The tags look like they > are not needed with the only one that *may* be useful being called "BIN" - > I have no idea what it is. Do you know? > > I will split the file into smaller sections for you and give you a link to > the download. Please give me a few days. I will aim to get it done by the > end on next weekend. If not then feel free to contact me to remind me. > > Rob > > > > _______________________________________________ > Imports mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/imports > > >
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