How to determine the scale

[Ed McNierney]

Ramesh -

MapServer will do all the reprojection for you.  You do not need to
convert your source data.  You simply specify the input projection
(lat/lon) for your input data and the output projection (LAEA) for the
map image.

To get started, use the MapServer Tutorial at
http://mapserver.gis.umn.edu/docs/tutorial/tutorial - there's a section
there on getting started with projections in MapServer.

	- 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: Ramesh Karra [mailto:karrarm at YAHOO.COM] 
Sent: Thursday, February 23, 2006 4:49 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU; Ed McNierney
Subject: Re: How to determine the scale

Thanks Ed,

Thank you very much for the quick response. How do I convert my lat/long
to a different projection, say LAEA? When I do this conversion, all my
shape files need to be re-created with this new projection co-ordinates,
right?
I have searched on the web, but could not figure out a way to convert
lat/long to LAEA. I really appreciate any pointers related to this.

Thanks
Krishna

On Thu, 23 Feb 2006 15:38:50 -0500, Ed McNierney <ed at TOPOZONE.COM>
wrote:

>Ramesh -
>
>If your output map image is in a "lat/long" projection - which yours 
>seems to be, since the extents are in degrees - then you really cannot 
>put a scale bar on the map.  Distances are not constant across such a 
>map, and depend on the latitude and the orientation of the line you're 
>measuring.  A one-degree North/South line is not the same length as a 
>one-degree East/West line (except if you're near the equator).
>
>If you want to put a usable scalebar on your map, measured in meters or

>miles, etc., you need to use a different output projection - one that 
>is designed to provide such measurements.
>
> - 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 Ramesh Karra
>Sent: Thursday, February 23, 2006 3:26 PM
>To: MAPSERVER-USERS at LISTS.UMN.EDU
>Subject: [UMN_MAPSERVER-USERS] How to determine the scale
>
>Hi,
>
>I have a map file with extent "74.3605 24.2590 79.5400 20.5070". I have

>a layer(with data in a shape file) with very few points
>
>75.23478 23.40182
>75.78261 21.90126
>76.37162 22.90461
>77.32890 20.88712
>
>The mapserver shows these points correctly. But it does not have 
>correct idea about the distance between the points. How do I indicate 
>the mapserver that these are latitude and longitudes and the distances 
>should be calculated correctly? Do I need to use scale? or some other 
>projection?
>
>I really appreciate any help in this regard.
>
>Thanks,
>Ramesh