[Talk-bd] The Kamal Ataturk Dual Carriageway

[Larry O'Neill]

Thanks Ishtiaque,

Anyone got any comments or questions on it?

Larry


On Fri, Jan 27, 2012 at 7:10 PM, Syed Ishtiaque Ahmed <ishtiaque at csebuet.org
> wrote:

> Thank you Larry for your contribution. I am sure this will help our young
> mappers.
>
> ishtiaque
>
> On Tue, Jan 24, 2012 at 6:12 AM, Larry O'Neill <larryoneill at gmail.com>wrote:
>
>> AAAH, the screenshots are too big for the email server to allow them.
>> I'll try to find a handy online location for them later so that you can
>> see them.
>> Or, you could open JOSM and look at the area around Banani Market and
>> Gulshan2 Circle....
>>
>> Larry
>>
>>
>> On Tue, Jan 24, 2012 at 11:09 AM, Larry O'Neill <larryoneill at gmail.com>wrote:
>>
>>> Hi Guys,
>>>
>>> This is my first descriptive document on my edits in Bangladesh, and I
>>> certainly hope it wont be the last.
>>> On the 7th of January, I submitted  osm.org/browse/changeset/10322877
>>> This is my description of why and how this was done.
>>>
>>> Dhaka has alot of dual carriageways - more than many cities I have been
>>> in.
>>> Navigating through Dhaka will almost always involve using a dual
>>> carriageway road at some point.
>>> This can introduce some interesting navigational challenges, as the
>>> physical barrier between the two carriageways imposes obvious restrictions.
>>> In many cases in Dhaka, turning right at a junction with a DC is not an
>>> option, left is the only way you can go.
>>> This reality is not really reflected if the dual carriageway is mapped
>>> as a single carriageway.
>>> An example of this exists here:
>>> osm.org/?lat=23.76438&lon=90.37224&zoom=16
>>> Mirpur road is marked on the map as a single carriageway, and so it is
>>> reasonable to assume that coming from Aurangajeb Road, you can drive
>>> straight to Lake Road, or turn right to go south on Mirpur Road.
>>> The concrete wall would decide otherwise if you tried this, and so the
>>> map doesnt really reflect what's on the ground.
>>> Navigational software based on this data will trust the data, and so the
>>> data needs to reflect the reality.
>>>
>>> This was the case with Kamal Ataturk, and so it was changed.
>>> The editing of it was relatively simple, but it did rely on the use of
>>> the Bing aerial imagery, and may not be entirely correct.
>>> The Bing imagery of Dhaka is an incredibly valuable resource
>>> [nb: I am a JOSM user, I havent dont any of this in potlatch, any
>>> potlatch users please feel free to reply with equivalent descriptions...]
>>> 1) open JOSM
>>> 2) go to File menu, Download from OSM. OR hit the download button on the
>>> main toolbar. OR hit Ctrl+Shift-D
>>> 3) select the area containing the road to be edited
>>> 4) download and allow it to render the data.
>>> 5) go to Imagery menu, Bing Sat.
>>> 6) after the background image has loaded, it may need to be moved
>>> slightly. Imagery menu, New offset.
>>> 7) use this to realign the imagery as well as you can. You may need to
>>> match it against existing OSM data or gps traces. Click and drag on the
>>> main editing pane.
>>> 8) hopefully the barrier between the two sides of the DC road will be
>>> visible, click and drag the current road to one side of the barrier for its
>>> full length. Realign or add nodes if necessary.
>>> 9) after moving the existing data to one side for the full length of the
>>> road, click the draw nodes button on the edit toolbar, and draw in the
>>> opposite carriageway for the full length.
>>> 10) make sure the direction of the existing way is correct, and change
>>> if necessary [click on a way and hit r to reverse it]. Add the oneway=yes
>>> tag to all sections of the existing way.
>>> 11) select the existing way and hit Ctrl+c to copy it. Click on your new
>>> way and hit Ctrl+Shift-V to paste the tags. This saves a lot of time.
>>> 12) edit any junctions along the road, showing where a minor road joins
>>> both carriageways, and where it only joins one side.
>>> 13) make sure that all possible movements at either and of the DC are
>>> maintained
>>> 14) upload the data and you're done!
>>>
>>> My first screenshot above shows the two junctions either side of Banani
>>> Market, where cars can be seen turning through a gap in the wall.
>>> The junction west of this reflects the restriction the continuous wall
>>> imposes.
>>> My second screenshot shows how the Gulshan end of the DC was terminated,
>>> allowing for all possible movements.
>>> This could have been achieved by joining all of the nodes at a single
>>> point in the centre of Gulshan circle.
>>> While that would have been topologically correct, and some would argue
>>> in favor of mapping it that way, it is my personal preference to do it as
>>> shown.
>>> Note also in my second screenshot the poorly aligned Bing imagery. This
>>> kind of alignment should be corrected before using it to edit.
>>> Another thing to note is the fact that the circular road around the
>>> Gulshan junction is cut a the two dual carriageway sections on  the south
>>> and west.
>>> The northern and eastern roads leading out of this junction are still
>>> incorrectly mapped as single carriageways.
>>> After doing this once, you may find it surprisingly quick to do it for
>>> another road in Dhaka or any other Bangladeshi town or city.
>>>
>>> If any of my edits on the Kamal Ataturk are incorrect, have restrictions
>>> where none exist, or would allow movement that cant be made, please feel
>>> free to change it.
>>> This is the beauty of collaborative and crowd sourced data - if it's
>>> wrong, correct it and move on! =0)
>>>
>>> I hope that the above description will be of some help to those that are
>>> new to the OSM project, and that we will soon see more Dual Carriageways
>>> mapped in Dhaka!
>>> Any comments, questions, criticisms, improvements or otherwise are
>>> welcome.
>>>
>>> Thanks
>>> Larry
>>>
>>>
>>
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>
>
> --
> Syed Ishtiaque Ahmed
>
>
>
>
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