5-20-98

This is a README for the Digital Elevation Model CD customer products:
This README addresses all scales of DEM data available on CD-ROM.


RECORD DELIMITERS:

The DEM files do not contain record delimiters.  You can add
delimiters by using the following commands:


For UNIX:
dd if=inputfilename of=outputfilename ibs=4096 cbs=1024 conv=unblock

For PC:
CHOP {record size} <{infile}> {outfile}
*note 1. the record size for DEMs = 1024
*note 2. the < and the > signs must be around the infile

The CHOP utility (chop.zip) can be found at:

     http://edcwww.cr.usgs.gov/doc/edchome/ndcdb/ndcdb.html

Refer to the public.html directory.
(This utility must be unzipped using PKunzip.)

DATA FORMAT:

Following is an example of the directory structure information for an
individual DEM file:

Format:  order_unit_file   file path
           |               |                            Resolution 
           |    ___________|        Alpha Directory         |  Version  
(7.5_MIN)  |   |                         |                  |    |
           V   V                         V                  V    V 
0000075_9966 /edcftp/pub/data/DEM/7.5min/C/cheesman_lake_CO/30.1.1.104928
                                               |               |   | 
                                               V               V   |___>File ID
                                           Quad & State      Level 
(15_MIN)

010980410000_1 /edceps1/eo/dg3ftp/pub/data/DEM/15min/F/fairbanks_d-1_AK/
                                                                  3.2.90918
                                                                  |
                                    resolution.level.file I.D. <__|
                                                                 
(30_MIN) (a.k.a. 2_arc-second; a.k.a. 100K) 

0049804070065_1_4 /edceps1/eo/dg3ftp/pub/data/DEM/30min/A/abbeville-e_SC
                                                               /GX4.EMF08.gz
                                                                |
                                          file I.D. with gzip <_|

(250K)

0119804240093_1 /edceps1/eo/dg3ftp/pub/data/DEM/250/S/sioux_falls-e

For specific information concerning the dataset, US GeoData users guides
are available through anonymous FTP at the following site:

ftp://mapping.usgs.gov/pub/ti/DEM/demguide

*** NOTE:  Make sure to set the file transfer mode to binary
           if utilizing FTP to receive data files.

or visit URL:

http://mapping.usgs.gov/pub/ti/

A more condensed version of the guide can be found at:

http://edcwww.cr.usgs.gov/glis/hyper/guide/usgs_dem

The Global Land Information System (GLIS) also provides on-line data set
documentation.

To acquire a printed copy of any users guide or for further information
about Internet access to U.S. GeoData files, call 1-800-USA-MAPS or
contact:
         U.S. Geological Survey
         EROS Data Center Customer Services
         Sioux Falls, SD  57198
         605-594-6151;  FAX 605-594-6589
         E-mail: custserv@edcmail.cr.usgs.gov

ORDER SUPPORT:

For order and accounting questions, please contact the USGS Earth Science
Informaiton Center (ESIC) site where your order was originally placed.