Relationship between Unit dd and MAX/MINSCALE

[Ed McNierney]

Tim -

If your units are DDs, you cannot express them in miles - it's
meaningless, since the distance between any two points on such a map (in
miles) depends on the latitude of the map and the angle of the distance
being measured.  This is one of the reasons using "geographic" output
projections for maps is, IMHO, a very poor practice that seems to be
infesting the Web mapping world.

     - Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: +1 (978) 251-4242
Fax: +1 (978) 251-1396
ed at topozone.com 

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Tim Tsai
Sent: Wednesday, April 27, 2005 5:33 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] Relationship between Unit dd and
MAX/MINSCALE

Hello.  I have a map file that uses UNIT DD (decimal degrees) but I
can't quite figure out exactly what unit the MAXSCALE/MINSCALE keywords
use.

For example, MINSCALE 100000 seems to be more than 3.2 miles but less
than 6.4 miles.

Thanks,

Tim