Scale and Map Units

[Stephen Lime]

As of 3.2.19 decimal degree scale computations are supported.
Regardless, you must set the UNITS parameter to the units of
your coordinate system. In your case use "UNITS DD". MINSCALE
and MAXSCALE then work like always athough you may have
to experiment a bit more to figure out the right values.

Remember that the DD support is based on the assumption that
x values are constant everywhere which is obviously false. So
DD based scalebars must be used cautiously as they are only
valid on the equator. If possible, best to use a localized projection
and coordinate system.

Steve

Stephen Lime
Internet Applications Analyst

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> Kieran Ames <kames at erols.com> 11/05/99 11:50AM >>>
Hello again. Kieran here (from my home address, not work!).

I have a question regarding scale and when to render layers and labels.

The data I work with is consistently in decimal degrees. For data I've
received that was in some type of projection, I converted those files to
dec degs.

The data I've seen in the examples around the list use image
_coordinates_. So, a map file entry like
EXTENT 74000 4775000 798000 5500000
might have another line like
MINSCALE 400000 and MAXSCALE 400000 for different layers.
(www.dnr.state.mn.us/mis/gis/gislis99/example4)

I've set my extent information in Decimal degrees like
EXTENT -74.257 40.496 -71.857 41.292  (Long Island, NY)

Questions:
1. What is the proper way of implementing MINSCALE and MAXSCALE
functionality using decimal degrees?
2. My scale bar works, but gives a range like 0.0000 to 0.0002 miles
when I'm looking at a layer that's more than 100 miles across... (Extent
above)

Many thanks.

Kieran