How to determine the scale

[Ed McNierney]

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