[HOT] Call for volunteers: Somalia roads import

andrzej zaborowski balrogg at gmail.com
Mon Aug 22 14:49:27 BST 2011


Some notes from me, I'm still working on a tile of the MadMappers data.

On 22 August 2011 14:51, Harry Wood <mail at harrywood.co.uk> wrote:
> Download the chosen .osm file and open in JOSM
>
> File -> new layer then download OSM data covering the same area (and a bit
> more). I needed to do this peice by peice because the are was too large for
> a single download (although not much data being returned by the server)
>
> Using the layers panel to flick between datasets. Visual compare. look for
> overlapping areas for road.

I prefer using the mapnik tiles (Imagery menu) as a background for
finding the duplicates, makes it easier to see which data is the new
and which is existing OSM data because of the different style.
Obviosuly some features are not on mapnik so it needs and additional
check later.

>
> For me there were no existing roads in OSM to worry about apart from in the
> town on Burao http://www.openstreetmap.org/?lat=9.5151&lon=45.5441&zoom=14
> I did a general sanity check on the rural roads data, comparing bing
> (landsat) The MadMappers roads are mostly not visible in this, but they
> seemed follow logical well lined-up paths through mountains and along valley
> bottoms. I decided to upload the data to OSM first (creating duplicates in
> Burao) and then make a few de-duping fixes after that.

In my case there's lots of existing data so there's lots of work on
deciding which is more exact in a given area and it's probably a good
idea to do the fixing up (deleting ways and joining at crossing) all
in the same changeset.  Or maybe that's just a programming habit to
preserve bisectability :)

>
> Go to openstreetmap.org  'logout' then 'sign up' to create a new user
> account for imports (if you don't already have one) e.g. 'Harry Wood
> Import'   Verify email address etc.
>
> back in JOSM  Edit preferences. 'Connection Settings' panel. Swap to new
> username and password
>
> Click upload. Set the source=MadMappers-SOM-2008-01  on the changset
>
> I had 13,000 objects. This took 20 or 30 minutes to upload as a diff. I'm
> not sure if there's a better (more robust and less strenuous on the server)
> way to do this. Perhaps switching to "atomic" mode would be a good idea for
> this.

There's probably no faster/less strenuous way but make sure to use an
atomic upload if you have < 50000 elements, rather than upload in
chunks, else there's always a risk of a broken upload.

>
> back in JOSM  Edit preferences. 'Connection Settings' panel. Swap to my
> normal username and password.
>
> Delete all layers and re-download the OSM and MadMappers data (now munged
> together on the server)
>
> --- Fixup ---
> From this point onwards I was just doing normal editing. Uploading
> regularly, and I didn't set a source tag (what is the source for fixing up
> an import? 'common sense'?)
>
> The existing data by User:roage was a few main roads in the town. These
> lined up pretty well with the data from MadMappers, but was more crude. It
> mentioned source=landsat in various places, although I hated to do this, I
> mostly deleted User:roage's contributions in favour of the MadMappers data.
> However User:roage's data included stuff off the edge of the area I was
> dealing with so this survived. I had to cut and re-connect these ways with
> the imported data (main roads coming into Buroa from the south west)
>
> In the MadMappers data itself there were some duplicates in the town. I
> didn't seed ways directly on top of each-other, but there was highway=track
> alongside highway=secondary. These were side-by-side like dual-carriageway
> or in places braiding over the top of each-other. Although this might have
> reflected some sort of reality, I'm guessing not, particularly as the
> highway=secondary was also surface=unpaved anyway. Clearly there is one main
> (but unpaved) road following this route through the town. So I guess this is
> the "doubled/overlapping roads" Schuyler is referring to. I imagine this is
> probably data from two surveyors munged together messily. So I deleted the
> highyway=track and made the necessary reconnections.

Additionally I've found a couple of named tracks which seem to
actually represent areas, not routable tracks.  I made the shapes
closed (they had small gaps) and tried to derive the tagging from the
name ("governors quarters", "meat packing plant", etc)

I also decided (wrongly?) to change all highwy=unclassified's to
highway=residential because all of them were in a town and it's
unlikely that there would be any roads that count as
highway=unclassified inside a town, please correct me if I'm wrong.

Cheers



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