August 1998

                         ******** Disclaimer ********

The General Cartographic Transformation Package (GCTP) is a system of
software routines designed to permit the transformation of coordinate
pairs from one map projection to another.  The GCTP is the standard
computer software used by the National Mapping Division for map
projection computations.  

Because of requirements internal to the EROS Data Center, the GCTP software
was converted from FORTRAN to the C programming language, and several new
projections were added.  During the conversion process, the software was 
tested on the following UNIX systems:  Data General running DG/UX Release
5.4R2.01 AViiON, SUN running SunOS Release 4.1.3, and Silicon Graphics
running IRIX Release 5.3 IP7.  In addition, the software has also been
verified against the current National Mapping Division (NMD) GCTP
software.  This new version, GCTPc, is being made available informally
on a 'user-beware' basis.  EDC assumes no responsibility for the accuracy
of the routines in this package.

Because of decreasing budgets and impacts on software development staff, 
EDC will not be responsible for supporting this software package.  The 
user is responsible for using the package correctly.  A set of validation
data is provided so that each user/facility may perform its' own testing
of the programs.  A description of this data set and instructions for its
use are in the test/README file.  EDC will welcome any questions, comments, 
or suggestions, and will respond on a time-available basis based on our 
interests and requirements.  Communications concerning the GCTPc package 
may be directed to this email address:

	gctpc@edcmail.cr.usgs.gov


--------------------------------------------------------------------------------

                         ******** Announcement ********


The General Cartographic Transformation Package (GCTP) was converted to the
C programming language, and several new projections were added.  This new
version, GCTPc, is being made available informally by EDC.  The directories
and files containing this package are available via anonymous ftp.

Periodic updates and corrections will be put in this directory for access
by the science community.  Descriptions of these updates will be added to
the README file in the main directory.

The Package has been tar'd and compressed under the directory name gctpc.
To access GCTPc, retrieve the file gctpc20.tar.Z by anonymous ftp from

	edcftp.cr.usgs.gov

This file can be retrieved by following these steps:

	ftp> cd pub/software/gctpc
	ftp> bin
	ftp> get gctpc20.tar.Z
	ftp> quit

Then on a UNIX system type:

	% uncompress gctpc20.tar
	% tar -xvf gctpc20.tar

The uncompressed gctpc20.tar file is approximately 38 megabytes in size.
A gctpc directory will be created and the files copied into it.  Since the
gctpc20.tar file is not automatically deleted, the installation will
require approximately 76 megabytes of disk space.  This will allow
the actual package files and gctpc20.tar to be on disk at the same time.