[OSM-talk] who moved Mumbai?

Shekhar Krishnan shekhar at crit.org.in
Sun Jul 6 19:05:38 BST 2008


I spent today attempting to grapple with these issues, with some success.
We've reprojected the WMS into wgs84 (EPSG:4326) from UTM 43N (EPSG:32643)
by reprojecting the shape files using ogr2ogr. This fixed the WMS problem,
and I have succesfully loaded these URLs for different layers from the
Mumbai Freemap in JOSM:

Buildings (Polygons)
http://mumbai.freemap.in/wms.cgi?srs=epsg:4326&format=image/jpeg&request=GetMap&service=WMS&version=1.1.1&layers=building_polygon_4326

Building Outlines (Lines)
http://mumbai.freemap.in/wms.cgi?srs=epsg:4326&format=image/jpeg&request=GetMap&service=WMS&version=1.1.1&layers=building_line_4326

Municipal Land Use Reservations (Polygons)
http://mumbai.freemap.in/wms.cgi?srs=epsg:4326&format=image/jpeg&request=GetMap&service=WMS&version=1.1.1&layers=reserved_polygon_4326

There are several other layers in http://mumbai.freemap.in that are not here
yet, and I will work on grouping and styling them so there is only one for
buildings and another for road and rail networks and send around new links.
A quick glance at the results in OSM shows that as reported, with the AND
data on OSM right now, everything has been moved east and north, though this
is not consistent and in Central Mumbai the offset seems to becomes less.

This raises the question of what to do generally about Mumbai in OSM. While
a WMS overlay looks nice and can be traced by volunteers with a great deal
of time and effort, I am more interested in directly loading these shape
files into JOSM and supplementing or replacing the AND data with our Mumbai
Freemap layers. I am happy to share these shape files with anyone in the OSM
community who might be able to lend a hand using osmlib, ruby-shapefile,
gml2osm, or any other method.

A correction to Mikel: the third dataset which you mentioned we have from
the Govt of Maharashtra PWD is not of Mumbai, but of the rest of the state,
and contains the entire road network, all village names and maps, and
district boundaries for Maharashtra. These are also shape files with their
own pecularities.

I've had issues both with JSOM and the WMS plugin which I'll also note here.
I'm a newcomer to both, so any help is appreciated. Downloading data for
Mumbai from OSM and from local OSM instances such as
http://demo.binyasit.com:3000/ almost always returns only a snippet of the
area which I select from the permalink. I'm not sure why, sometimes I get
the fulll boundaries of Greater Mumbai and then a handful of nodes.

Also, the WMS plugin is not very good at saving changes made to new entries,
which often revert to the previous saved entry after restarting JSOM. This
has made it difficult to keep track of which WMS URL is being called as the
menu is not refreshed after saving a URL and restarting JSOM. The other
issue, which Chippy raised, is the lack of UTM support in the WMS plugin
which should be addressed as we would rather use our UTM projection fof
maximum accuracy.

Thanks for the help and support!

Best,


Shekhar

2008/7/6 Tim Waters (chippy) <chippy2005 at gmail.com>:

> UTM which EPS:32643 appears to be, could be implemented within the
> wmsplugin.
>
> The WMSplugin uses some classes from jcoord, to convert from OSGB
> (what the NPE wms server uses) to wgs84. (OSGB is itself Transverse
> Mercator too)
>
> Looking at the jcoord package, it also has classes to convert from UTM
> zones also :
> http://www.jstott.me.uk/jcoord/api/1.1-b/uk/me/jstott/jcoord/UTMRef.html
> So I'd think the wmsplugin could be hacked to get it working
> reasonably easily.
>
> Regards,
>
> Tim
>
> _______________________________________________
> talk mailing list
> talk at openstreetmap.org
> http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
>



-- 

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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