Data Download Guide

Data in the GLCF archive can be quickly and efficiently downloaded by any user. This guide is provided to explain available download options. Anyone with questions may contact the GLCF directly. For beginners, the following steps should be followed, while advanced users can proceed directly to ESDI or collection specific FTP sites.

1. Choose Type of Download
A. Visit the GLCF Data & Products page. Choose the data collection of interest by clicking on the hyperlinked collection name. For example, to choose the Landsat imagery collection, first look under the Imagery section, then click on the Landsat header.
B. Each data collection's Overview page will have a section at the top called "Data Access" where the types of data access available for the collection are specified. Click on one of the options to continue. Note that not all options are available for every collection.




2. Download via Search and Preview Tool (ESDI)
Most GLCF collections can be searched and previewed by users in the Earth Science Data Interface (ESDI). This tool allows users to select files based upon collection type, location, date, or a mixture of parameters. Please open ESDI and review the Help pages for Map Search, Product Search, or Path/Row Search, and then the pages for Preview and Download to operate ESDI. Once a selection has been made, continue, below, with FTP page operations.


3. Download via FTP Server
This option provides users direct access to the top of the directory structure where this collection's files are located. There are no search or preview functions available, but some users who know the name of their targeted files may access and download directly using this option. Once an individual product or image scene's FTP page has been located, continue, below, with FTP page operations.


4. Download via Map Selection
Where some GLCF collections are not yet available in ESDI, maps have been created for users to locate files. Use the maps to determine which hyperlink will provide access to files. Click on a link and the chosen product or imagery scene will become available as files in an FTP directory. Continue, below, with FTP page operations.


5. Download via Restricted Access
Most GLCF collections are available to everyone, but some are restricted to specific groups. In these cases, the GLCF is required to follow redistribution restrictions from the imagery or product source. Please follow instructions as indicated with these collections. Once an individual product or image scene's FTP page has been located, continue, below, with FTP page operations.


FTP page operations
The files available for download are visible on an FTP Page similar to Figure 1. To begin downloading, simply click on one of the file names and that file will copy to the user's computer. Note that metadata files, preview image (thumbnail) files, and browse files are available for download in addition to the actual spatial data. Preview and browse images may be available in multiple band combinations.


Figure 1. Example of a GLCF FTP Page.



6. Uncompress spatial data files

Large spatial data files are often compressed so that users can more quickly download. Files must be uncompressed before they can be used.

A. Some browsers automatically uncompress data upon download. Compare the file size of downloaded data to that described on the FTP page (as on Figure 1). If the file size matches that in the "Download Size" column, then it may be necessary to uncompress the file. If the size matches "Actual Size" then the file was already uncompressed.
B. Compare the name of the downloaded file with that on the FTP page (as on Figure 1). Verify that the name is exactly the same, including any ".gz" extension. The ".gz" indicates the file is compressed. Browsers sometimes drop the extension when downloading. If this happens, and the file is not recognized in the next step, then change the file name to match the FTP page.
C. The compression software used by GLCF is the industry standard for large files - the gzip utility. Either uncompress files using the gzip software itself, or another compression software such as WinZip that will handle gzip format. The result should be a file with the same name (except for the ".gz" extension) but a much larger file size. This file is now ready to use in spatial data software.