[Imports] Tanzania buildings

Rob Nickerson rob.j.nickerson at gmail.com
Wed May 21 19:56:26 UTC 2014


I can't get to the download page - I just get a login prompt. Not sure why
because your previous upload was fine.

How have you got on contacting other OpenStreetMap contributors in this
area? There are a few tools that you can use, for example:


It would be good to also contact the mappers who have added some of the
existing buildings in this city. Do you know how to work out who mapped
them? If not then let me know what OSM editor you are using and I'll
provide instructions.


On 19 May 2014 21:32, msilikale msilanga <msilikale05 at yahoo.com> wrote:

> Hello Rob and Mikel,
> Since you game me your advice, i have been working on the data and I have
> finally Georectified them. You can find them here
> https://www.dropbox.com/home/Rectified%20Dar%20Buildings for more advice
> on how to do the import in Open Street Map.
> Thanks for the advice and i would be happy to get these data into the OSM.
> Best,
> Msilikale Msilanga
> +255717506053
> Skype: msilikale05
>   On Sunday, April 27, 2014 5:43 PM, Rob Nickerson <
> rob.j.nickerson at gmail.com> wrote:
>  Msilikale,
> I've checked against the GPS data we hold in OpenStreetMap (there is a
> particularly good GPS track of someone walking round the edge of what looks
> like a cricket pitch) and can confirm that there is a bad offset in the
> building data. I expect it's either been traced against offset imagery or a
> re-projection somewhere along the line hasn't been quite right.
> I also have concerns about the quality and age of the data.
> As I don't feel able to resolve the offset issue (it's not my area of
> expertise) I'm unable to help you any more. Someone else on the mailing
> list may be able to help, but at some point you need to make a judgement
> about the data quality with your local community.
> Rob
> On 25 April 2014 19:23, Rob Nickerson <rob.j.nickerson at gmail.com> wrote:
> 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" <mikel_maron at yahoo.com> 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 <
> rob.j.nickerson at gmail.com> 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
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