[OSM-talk] who moved Mumbai?

Mikel Maron mikel_maron at yahoo.com
Sun Jul 6 06:26:43 BST 2008


Hi

Let me see if I can summarize the current data sets available in Mumbai.

* In February, Martijn imported AND data for India, including great detail over Mumbai. However, when examining the data post-import with locals, we discovered there was no consistent offset on the data .. there were a large number of inconsistencies and errors. Consulting with AND, we learned that Mumbai data was largely a side project of AND employees of untraced origin. It's likely this data was created without much regard for geographic or feature accuracty.

* The Mumbai Freemap data was prepared for the web a couple years ago. That data is available as a WMS, though there are currently some unknown issues with incorporating that WMS server into JOSM.

* There is now new data available fromthe Maharashtra Dept of Public Works, including quite a few data layers. (Maharashtra is the India state in which Mumbai is situated). That data is stored in some funky Shapefiles. 


The question is where to go from here. Technically there are two main needs. Can anyone volunteer a little time on...

1) Get the Freemap server serving WMS requests to JOSM correctly.
2) Write conversion scripts for the Shapefiles into OSM. My thinking is that a ruby script, using osmlib and ruby-shapefile is the most straightforward way to go.


With these technical problems passed, we'll have three data sets to work with and compare. JOSM can handle this, though it might through up some usability issues with such large data sets. We may discover that parts of AND Mumbai are so jumbled that it's better to clear the slate and start fresh by importing MDPW data, or tracing Freemap. I don't think all of Mumbai will have this problem -- the older parts of Mumbai are likely to be more accurate. Locals will need to look at this area by area, and make judgements, and the whole effort organizing as a WikiProject Mumbai on the OSM wiki.

Mikel




----- Original Message ----
From: Shekhar Krishnan <shekhar at crit.org.in>
To: OSM Talk <talk at openstreetmap.org>
Sent: Saturday, July 5, 2008 2:32:02 PM
Subject: Re: [OSM-talk] who moved Mumbai?

Since someone mentioned the Mumbai Freemap [1] into OSM, I thought I would finally introduce myself to the list. I am coordinator of the project, which was developed in 2005-2006 to showcase the kind of geo-data being collected by volunteers in Mumbai's architect and activist communities connected to CRIT (Collective Research Initiatives Trust) [2]. 

The data itself is poorly formed, having been originally drawn in AutoCAD without geographic attributes and retrospectively warped into shape files from sets of disconnected lines and attribute tables [3]. In our community mapping project, we now hope to merge our base layers into OSM and train groups in JOSM to detail particular areas, which we can use as the basis for projects on public spaces, community housing and heritage conservation in Mumbai. 

For some time now we have wanted to contribute this data to OSM, and we now have devoted funds from UNDP [4] which we plan to use in support of OSM as an infrastructure for our research and design practice. Earlier this year Mikel Maron and Schuyler Erle organised a series of Freemap/OSM  workshops [5] which seeded new communities in cities across India, and in Mumbai generated significant interest.

We think that the existing Mumbai Freemap is mostly useful as a backdrop (WMS) against which new nodes and relations need to be traced and tagged within OSM, and we are determined to migrate our vector data into OSM in stages over the next few months. Chris Schmidt wrote this script [6] to migrate MassGIS shape files into OSM. 

Any suggestions on how best to approach this SHP to OSM migration and the wider goals of our project are most welcome! 

Best, 


Shekhar

[1] http://mumbai.freemap.in
[2] http://crit.org.in
[3] http://wiki.freemap.in/moin.cgi/MumbaiFreeMapDatabase
[4] http://www.apdip.net/projects/ictrnd/2005/l43-in/
[5] http://wiki.freemap.in/moin.cgi/FreeMapIndia2008
[6] http://boston.freemap.in/osm/files/mgis_to_osm.py




2008/7/5 Nathan Vander Wilt <nate-lists at calftrail.com>:

On Jul 5, 2008, at 1:01 AM, Kenneth Gonsalves wrote:
> On 05-Jul-08, at 3:24 AM, Frederik Ramm wrote
>>

>>> everything is AND and everything is consistently out of place to
>>> the  southeast with the same offset - is there any way to
>>> programmatically  change this?
>>
>> I have a script that I could use for this task if people want.
>> Obviously I'd need to know exactly what to move and by what amount...
>
> cool - will measure the offset and revert

Are you sure this isn't a coordinate system datum issue? If the AND
data uses a different datum than WGS-84, it may be more than just a
simple offset for all vertices that you need. There are several open
source programs available for converting from one datum to another.
What datum is the original AND data in?

thanks,
-natevw


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-- 

Shekhar Krishnan
9 Supriya, 2nd Floor
Plot 709, Parsee Colony Road no.4
Dadar, Mumbai 400014
India

http://web.mit.edu/shekhar
http://heptanesia.net
http://bombayology.net 
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