MAPGEN

[Gerald I. Evenden]

In reference to the previous two grassu-list mailings:

>Nancy Gardner has posed the following questions.
>email: ngardner at ncrds.er.usgs.gov

>From: jschuler at ncg.scs.ag.gov (Jill Schuler)
>To: ngardner at ncrds.er.usgs.gov, grassu-list at max.cecer.army.mil

I won't repeat the message and response as they are long, but they
prompt me to make a couple of comments, one minor and the other
a little more critical.

On soapbox.

First: there are probably well over 400 cartographic projections
and along with this number there is often a problem of nomenclature with
some  projections having more than one name.  Multiple names
can only add to the confusion of proper projection identification.

In the Gardner/Schuler discussion a "latitude-longitude" projection
is mentioned which appears to be equivalent to the proper and more
descriptive names of Equidistant Cylindrical, Equirectangular or Plate Caree.
Thus we have added one more level of confusion to an already confusing
situation.  To add to the confusion, the name is derived from the
names of the axis of a coordinate system.

I know I am going to be ignored in this windmill tilt, but I truly
wish that "latitude-longitude projection" be struck from polite
conversation.

Second (and to me a more sever criticism): MAPGEN is designed to be
very flexible in the selection of cartographic projections.  Only two
restrictions were imposed: 1) the ability to accurately perform the
projection process in large and medium scale applications and 2) allow
for a wide variety of cartographic projections.  The second factor is
only limited by the capabilities of the program proj, which currently
supports over 100 cartographic projections.  But what has happened, is
that wrapper scripts, in a laudable effort to simplify usage, tend to
emasculate the flexibility of the system.

In this case, I shudder to think that +proj=eqc can't be used and "MAPGEN"
gets a reputation for not being able to handle a common projection
(that it can under different usage circumstances).

I wish we could engineer a better communication mechanism with the
MAPGEN system than what seems to be available now and I would volunteer
whatever help I can to this end.  Hey, if we could get to some
consensus, I would even make another mapdef program, which is where
the user interface hangup seems to lay.

Off soapbox.

Gerald (Jerry) I. Evenden   Internet: gie at charon.er.usgs.gov
voice: (508)563-6766          Postal: P.O. Box 1027
  fax: (508)457-2310                  N.Falmouth, MA 02556-1027