A Fiducial site is a geographic location that is used as a benchmark for the long-term monitoring of processes, both natural and anthropogenic, associated with the causes and effects of global environmental change. The word fiducial carries multiple meanings with regard to the Global Fiducials Program (GFP). Fiducials are marks or points of reference applied to images to present a fixed standard of reference, so in the GFP they refer to the identification of a place on the Earth. The term fiducial may also be interpreted to refer to a long-term trust, where one may be holding something in trust for another. Both references aptly apply, as the GFP maintains a long-term record of data over specific places on the Earth to be available for scientific investigations. Fiducial sites are associated with Earth processes and environmentally sensitive areas that are being monitored so that scientists can better understand and model the dynamic systems and changes that are occurring. The sites are located around the globe and are distributed among environmental topics and processes within five major disciplines: Ocean Processes; Land Use/Land Cover; Atmospheric Processes; Ice and Snow Dynamics; and Geologic Processes.

GFP Sites Map displays Fiducial site locations. The sites are organized by geographic region (Domestic U.S., International, Arctic Sea, and Antarctica). Start by selecting a geographic region using the navigation button on the top of the page. Each geographic location page contains a drop-down list on the top-left that contains all the sites for which data are available in that region. Also each page includes site information.

The data can be viewed and downloaded from the Image Viewer or Image Gallery. In both, the data are organized by geographic region (Domestic U.S., International, Arctic Sea Ice, Arctic Sea Ice Buoys and Antarctica). Start by selecting a geographic region using the navigation button on the top of the page. Each geographic location page contains a drop-down list on the top-left that contains all the sites available in that region.

Image Viewer allows you to view GFL imagery in the interactive map using the Time Slider. The map for each region is displayed in an appropriate map projection for the region:

• Domestic U.S. & International: WGS 1984 Web Mercator (Auxiliary Sphere) Projection
• Arctic Sea: WGS 1984 North Pole Lambert Azimuthal Equal Area Projection
• Antarctica: WGS 1984 South Pole Lambert Azimuthal Equal Area Projection

In order to optimize performance of the Time Slider, for some GFP sites only a selected set of imagery can be viewed and downloaded from the Image Viewer. However, a complete set of available imagery can be viewed and downloaded from the Image Gallery. For Image Viewer instructions, go to Image Viewer Help.

Image Gallery displays the thumbnails of all imagery available for each GFP site in chronological order. It provides download links to imagery and metadata files. For Image Gallery instructions, go to Image Gallery Help.

This website contains data derived from U.S. National Imagery Systems. These data are available for public use.

The ground sample distance of these data is one meter. Each pixel is one meter by one meter.

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

The data that can be acquired through this website is 8-bit data.

All of the data found on this website have been orthorectified.

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.

The data are available as both a GeoTIFF and a GeoPDF.

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.

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)

There is no cost to download data from this website.

Initially, data from this website will only be available through download. Use the Contact Us button on the top of any page on this website to request consideration for alternative access to the data.

The data available for download through this website are completely unrestricted and may be distributed freely.

Corresponding vector data are not currently available through this website. However, vector data for these areas may be available through the USGS at:

• Earth Explorer, USGS EROS Data Center	http://earthexplorer.usgs.gov
• The National Map, USGS	http://nationalmap.gov

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.

We will answer additional questions not referenced in this FAQ list through the Contact Us button on the top of any page on this website.

All of the data available for download through this website are completely unrestricted and may be distributed freely.