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How To: Download and prepare DEMs for import to ArcView

Summary

Instructions provided describe how to acquire DEM data and prepare it for ArcView. See the documents referenced in the Related Information section of this document for details on DEM data.

Procedure

Data can be downloaded from an FTP site by using one of the many free GUI-based File Transfer Protocol (FTP) programs available on the Internet.
Files can also be downloaded using the command line FTP DOS application that comes with Windows operating systems.

Downloading data

The Windows Operating System comes with a command line File Transfer Protocol (FTP) application that is used to download files from an FTP server.
  1. Open a DOS command prompt.
  2. Enter the FTP command at the prompt:
C:>ftp
  1. Enter the open command and the address of the FTP server at the FTP prompt.
ftp> open ftp.yourwebsite.com
  1. Enter a username for the server. Many FTP servers allow an anonymous login.
username: anonymous
  1. Enter a password. The password for an anonymous login is your email address.
password: johndoe@youremail.grp
  1. Change to the directory where the file resides.
ftp> cd pub\data\directory
  1. Change the directory of the local machine to the location that is to store the download files.
ftp> lcd c:\downloads
  1. Set the data transfer type to binary.
ftp> bin
  1. Use the get command to retrieve the file.
ftp> get filename
  1. Exit FTP.
ftp> bye

Uncompressing data

If the USGS data files are obtained in a compressed format, they must be uncompressed before they can be used in ArcView. When downloading data from an FTP server, the server may automatically uncompress the file as it is downloaded. To evoke this feature, leave off the .gz file extension when selecting a filename. If the FTP server is not capable of uncompressing the file, use a utility such as GZIP or WinZIP. Once the data is decompressed, add a .dem extension to the file.
Warning:	The data may become corrupt if using an Internet browser to download the data. Instead, download the data using the Windows command line FTP utility.

Related Information