Global Fiducials Library Data Access Portal - About

GFL Data Downloads and Specifics

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Get Data

The data can be viewed and downloaded from the Image Gallery. The data are organized by geographic region (Domestic U.S., International, Arctic Sea Ice, Arctic Sea Ice Buoys and Antarctica). The image gallery is broken into geographic regions.   Each geographic location page contains a drop-down list on the top-left that contains all the sites available in that region. 

The GFL image gallery displays the thumbnails of all imagery available for each GFP site in chronological order. It provides download links to imagery in GeoTIFF and GeoPDF format along with corresponding metadata files.

Is the data free?

GFL data is derived from U.S. National Imagery Systems. These data are free and available for public use.  The data are completely unrestricted and may be distributed freely.  Data can be used in publications and study.

Specifics on GFL Data

The ground sample distance of these data is one meter. Each pixel is one meter by one meter and is 8-bit data.  All of the data found on the image gallery have been orthorectified.

Horizontal positional accuracy of approximately 9 meters should be expected, but actual accuracy of individual products is not measured and may vary significantly.

Metadata is available along with the data in an FGDC-compliant format. The metadata file has an .XML extension. The metadata file will open in any web browser. Metadata means "data about the data", hence each metadata file carries information about the image file. Location information indicating where the image is located on the earth is recorded in the metadata file.

What is a GeoTiff?

GeoTIFF refers to TIFF files which have geographic (or cartographic) data embedded as tags within the TIFF file. The geographic data can then be used to position the image in the correct location and geometry on the screen of a geographic information display. GeoTIFF is a metadata format, which provides geographic information to associate with the image data. But the TIFF file structure allows both the metadata and the image data to be encoded into the same file. GeoTIFF makes use of a public tag structure which is platform interoperable between all GeoTIFF readers. 

Many systems today can read GeoTIFF files into correct geographic position in a variety of Geographic Information Systems (GIS), Image Processors (IP) and Computer Aided Design (CAD) software. You need to check with your system provider to find out if module to read/write GeoTIFF imagery is available for the software version which you use.

What is a GeoPDF?

GeoPDF is a published extension (OGC 08-139r1) to the Adobe PDF file format, from TerraGo Technologies. It is used to present GIS and mapping data in a standard Adobe Systems PDF. This extension adds a coordinate transformation matrix and other metadata to allow transformation of PDF coordinates to a projected Cartesian coordinate system. GeoPDFs often include other advanced PDF features such as layers and object data which can add significant GIS functionality to the file, particularly when used with the TerraGo Toolbar®. (Requirements: Windows desktop or web browser (TerraGo Toolbar® does not operate on Mac OS); Adobe Reader version 9.x, X.x or XI or Adobe Acrobat)

Vector data for these areas may be available through the USGS at:
Earth Explorer, USGS EROS Data Center 
The National Map, USGS   
Additionally, other Federal and local government sources, academia, and many commercial vendors may be able to provide vector data for the geographic areas referenced on this website.

Tecnical Support

Reference our contacts for further GLF data questions or guidance.

Contacts

Steven J Smith

Physical Scientist
Global Fiducials Library (Team Lead)
Phone: 703-648-7826

Chelsea Carbo

Geographer
Global Fiducials Library
Phone: 703-648-6692

Chelsea Cook

Geographer
Global Fiducials Library
Phone: 703-648-5140