Projection Need Help

[Rep Xxxxxxxx]

Hello Ed McNierney,
Thanks for your valuable suggestions. As you have mentioned, DLTM will be a
best choice for my application.

Best Regards,
vdharan


On Mon, 22 Aug 2005 11:38:21 -0400, Ed McNierney <ed at TOPOZONE.COM> wrote:

>Vdharan -
>
>Use of the lat/lon projection is, IMHO, generally a very bad idea.  It
>can create important distortion and makes it impossible to do something
>as simple as put a meaningful scalebar on the map.
>
>The UTM and DLTM projections are both Transverse Mercator projections,
>with similar properties.  In your case, you would have data in UTM Zone
>39, with a central meridian of 57 degrees East.  The DLTM is exactly the
>same projection, with the central meridian at 55 degrees 20 minutes
>East.  This is a very small difference, and most non-technical users
>will never notice the difference.
>
>The choice of projection depends on the area you need to cover.  If you
>are only going to be mapping Dubai, or only the UAE, then I'd recommend
>you choose the DLTM projection.  That would be the standard projection
>in use for official Dubai or UAE data sets, and might make it easier to
>integrate future data from those sources.
>
>If, however, you intend to cover a larger area, the UTM would be a
>better choice.  The DLTM projection would not be used outside of the
>UAE, and if you're covering several independent countries there's no
>particular reason to choose one "national" projection over another.  A
>"regional" projection such as UTM would probably be a better choice.
>
>There is really very little practical difference between these two
>projections; it's just a matter of where your application will be used.
>
> - Ed
>
>Ed McNierney
>President and Chief Mapmaker
>TopoZone.com / Maps a la carte, Inc.
>73 Princeton Street, Suite 305
>North Chelmsford, MA  01863
>ed at topozone.com
>(978) 251-4242
>
>-----Original Message-----
>From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
>Behalf Of vdharan
>Sent: Monday, August 22, 2005 8:07 AM
>To: MAPSERVER-USERS at LISTS.UMN.EDU
>Subject: [UMN_MAPSERVER-USERS] Projection Need Help
>
>Hi
>
>Iam using MapServer (php mapscript)for Online vehicle tracking
>system.Iam also using rosa applet to show online movement of multiple
>vehicles on the map.
>
>The application is going to be used in Midddle East. While designing the
>system I have used some sample shape files for that region with lat long
>projection. Now are trying to get shape files with all road level
>details.
>The map vendor has got maps with WGS84 UTM and WGS84 DLTM(Dubai Local
>Transverse Mercator) projections. I dont know which projection to select
>for my application. I have used lat long projection and developed the
>application.I need to pinpoint the vehicle location based lat & long. If
>I go for UTM will that involve changs in the mapping codes?.  Iam from
>electronics background, I could not understand much on projection.
>Please Help me.
>
>Best Regards,
>vdharan