GFL Data Access Portal
Image Viewer Help
Important Notice about the Image Viewer
The Image Viewer displays only a selected set of imagery for some GFP sites. A complete set of available imagery can be viewed and downloaded from the Image Gallery.

Finding Data
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.

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

Default View
By default GFL data are displayed with some transparency over World Imagery Basemap.
Default Map View with Basemap
To hide the Basemap, move the Opacity Slider to 1.0 or select "Hide Basemap" option in "Basemap" menu.
Map View without Basemap

Basemaps/Data Layers
Basemap Button Click this button to view thumbnails of available basemaps. Only one basemap can be used at a time. Click the thumbnail to select a different basemap. This function is available only for the Domestic U.S. and International regions.
Imagery A collection of multi-resolution aerial and satellite imagery. Data Source: Esri, DigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community.
More Information   Map Service URL
Topographic A collection of administrative boundaries, cities, water features, physiographic features, parks, landmarks, highways, roads, railways, airports, land cover and shaded relief compiled from a variety of sources. Data Source: Esri, DeLorme, NAVTEQ, TomTom, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, and the GIS User Community.
More Information   Map Service URL
Shaded Relief The shaded relief imagery developed by ESRI using GTOPO30, Shuttle Radar Topography Mission (SRTM), and National Elevation Data (NED) data from the USGS.
More Information   Map Service URL
LandSat Esri Image Service containing 30-meter global False Color LandSat imagery from 1975-2010. Data source: Global Land Survey (GLS) datasets (1975, 1990, 2000, 2005 and 2010) created by the USGS and NASA using LandSat images.
More Information
Data Layers Button Click this button to view the thumbnail of other data which can be viewed in the selected region. Click the thumbnail to display the data. This function is available only for the Arctic Sea Ice region.
Sea Ice Classification To be added.

Map Navigation - Default Functionality
The following mouse and keyboard map navigation is available by default. In addition, a zoom bar is available in the upper left of the map.
Zoom In
  • + key to zoom in one level, OR
  • Mouse Scroll Forward, OR
  • Double Click, OR
  • SHIFT + Drag the mouse
Zoom Out
  • - key to zoom out one level, OR
  • Mouse Scroll Backward, OR
  • SHIFT + CTRL + Drag the mouse to zoom out
Pan
  • Drag the mouse, OR
  • Use arrow keys to pan
Re-center
  • SHIFT + Click to re-center

Overview Map
The Overview Map can be opened /closed by clicking the arrow Overview Map Arrowon the bottom-right corner of the main map.
Overview Map

Measure Tools
Measure Tools Button Click this button to show the Measure Tool menu.
Measure Distance Icon  Distance Clicking this menu option activates the Measure Distance Tool and disables map navigation. Sketch a line by clicking on the map to create vertices. Double-click to end the line. The measurement is displayed on the result dialog box.
Measure Area and Perimeter Icon  Area & Perimeter Clicking this menu option activates the Measure Area & Perimeter Tool and disables map navigation. Sketch a polygon by clicking on the map to create vertices. Double-click to end the polygon. The measurements are displayed on the result dialog box.
Measure Distance Icon  Deactivate Clicking this menu option deactivates the Measure Tool, clear graphics and reactivates map navigation.

View Images using Time Slider
To activate the Time Slider, select "Time Slider" View Option. The Time Slider appears below the map. This view option is default. If the Time Slider is not visible when this view option is selected, refresh the browser.
Time Slider
Use the following buttons to operate:
Time Slider Click and drag to manually move the Time Slider.
Time Slider - Auto Play Click to auto-play the time slider.
Time Slider - Forward/Backward Click to move the Time Slider forward/backward by one tick.

View Images by Image Dates/Download Files
When "Image Dates" View Option is selected, the image item list appears below the map. Each item includes a radio button, the image file name & image date, and download links:
File Item
To display an image in the map, click the radio button. To download the image file, click the "TIFF" link to download it as a GeoTIFF, or the "PDF" link to download as a GeoPDF. Both GeoTIFF and GeoPDF image files are downloaded in a zip file. Once downloaded, the image file can be extracted using software programs such as as 7-ZIP or WINZIP in the Windows environment, or GUNZIP in the UNIX environment. To view the metadata, click the "XML" link. The metadata file will open in the web browser and can be saved by selecting "Save Page As" in the web browser menu.

For many GFL sites, more images are available in addition to those displayed in the Image Viewer. A complete set of available imagery can be viewed and downloaded from the Image Gallery. To go to the Image Gallery, click "Go to Image Gallery to View/Download More Data" link on the top of the image item list.