| 1: Where do these data come from? |
A: This website contains data derived from U.S. National Imagery Systems. These data are available for public use. |
| 2: What is the ground sample distance of these data? |
A: The ground sample distance of these data is one meter. Each pixel is one meter by one meter. |
| 3: Is metadata available for these data? |
A: Metadata is available along with the data in an FGDC-compliant format. The metadata file has an . XML extention. 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. |
| 4: What formats are these data available in? |
A: The data are available as both a GeoTIFF and a GeoPDF. |
| 5: What is a GeoTIFF? |
A: 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 any and all GeoTIFF-savvy 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) softwares. You need to check with your system provider to find out if they have written the software module to read/write GeoTIFF imagery in the software version which you use.
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| 6: What is a GeoPDF? |
A: 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 Desktop plugin to Adobe Reader. (Note: Adobe Reader version 7.x, 8.x, 9.x or Adobe Acrobat must be installed before TerraGo Desktop is installed.) |
| 7: How do I download the data? |
A: A link is available for each site that will enable you to download the data as either a GeoTIFF or a GeoPDF. Downloaded files will be zipped for compression purposes. Once downloaded, files can be decompressed using software programs like PKUNZIP or WINZIP in the DOS or Windows environment, or GUNZIP in the UNIX environment. |
| 8: How long will it take to download GeoTIFF or GeoPDF files from this website? |
A: Data download time via HTTP may vary greatly depending on your available bandwidth, the size and number of files selected, and the total burden on the systems being accessed. |
| 9: What is the cost to download these data? |
A: There is no cost to download data from this website. |
| 10: Can I order these data on DVD? |
A: 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. |
| 11: Can I distribute these data? |
A: The data available through this website are completely unrestricted and may be distributed freely. |
| 12: Are these data orthorectified? |
A: All of the data found on this website have been orthorectified. |
| 13: What is the bit depth of these data? |
A: The data that can be acquired through this website is 8-bit data. |
| 14: Are vector data available for download over these areas of interest? |
A: Corresponding vector data are not currently available through this website. However, vector data for these areas may be available through the USGS at:
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.
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| 15: Is there any technical support provided for using these data? |
A: 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. |
| 16: Should I worry about using data derived from U.S. National Imagery Systems in my publication or study? |
A: All of the data available through this website are completely unrestricted and may be distributed freely. |
| 17: How do I cite this website as a reference? |
A: Examples:
| Example 1: |
United States Geological Survey (2009, August 19). [Arctic Sea Ice Sites.]
Global Fiducials Library. [Retrieved October 19, 2009 from http://gfl.usgs.gov/gallery/beaufo_pub_gallery.shtml#gallery1] |
| Example 2: |
United States Geological Survey. [Arctic Sea Ice Sites.]
Global Fiducials Library, 19 October 2009.
[http://gfl.usgs.gov/gallery/beaufo_pub_gallery.shtml#gallery1] |
Replace all text in the '[]' with appropriate text for your useage.
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| 18: How do I find out what sites are included in the GFL? |
A: Future versions of this website will present the total distribution of sites included in the GFL. |
| 19: What web browsers does the GFL website support? |
A: The GFL website has been tested in IE v6, IE v7, Firefox v3, Netscape v8.
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| 20: What is the horizontal positional accuracy of the data? |
A: Horizontal positional accuracy of approximately 9 meters should be expected, but actual accuracy of individual products is not measured and may vary significantly.
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U.S. Department of the Interior |
U.S. Geological Survey