General Information:
The Seamless Data Distribution System (SDDS) is the ultimate location to explore and
retrieve data. U.S. Geological Survey (USGS) and the EROS Data Center (EDC)
are committed to providing access to geospatial data through The National Map.
An approach is to provide free downloads of national base layers, as well as other geospatial data layers.
These layers are divided into framework categories.
- Places
- Structures
- Transportation
- Boundaries
- Hydrography
- Orthoimagery
- Land Cover
- Elevation
Along with providing access to the data, the site contains:
- Tutorial to help with downloads
- Information about the downloadable products
- Frequently Asked Questions
- Links to product homepages and information pages
The SDDS is always growing with new data, tools, features, and much more.
SDDS capabilities include:
- Free downloads up to 1.6 Gbytes of data in 100 MB files in one request.
Users have unlimited access to the interactive map and can make unlimited requests.
The amount of coverage area depends on the number of products selected for download. For example, if
NED 1 Arc Second is selected as the only product a user can download up to a 30 square degree
area. But, if NED 1 arc second and NED 1/3 arc second are selected, then the area available for
download will be considerably smaller. To see the various sizes of coverage area
for each product, click on the List of Products drop down, select the desired product.
- User can define an area of interest by drawing a box, defining coordinates, or use available
templates to cut out the area.
The first method of drawing a box (square or rectangle) is best for defining a general area. The coordinates are
displayed, in decimal degrees, in the bottom left corner of the window as the mouse is moved over the map.
The second method of defining coordinates can be used when the user wants a precise area and knows the corner coordinates.
The third method is the use of provided templates, such as 7.5 min quadrangles.
- NEW Feature (8-07-2007) -- Tiled Data Distribution System (TDDS)
The Tiled Data Distribution System (TDDS) allows a user to access historical data from the
EROS storage system. The concept of SDDS is to provide the best available data. In the case of
the high resolution orthoimagery, the best available will change approximately every couple of years.
The older imagery will be removed from SDDS and map services and made available using TDDS.
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- Query tools are provided to acquire more information about the an area of interest.
An example of the two query tools are Elevation Point and Elevation Profile. The elevation point tool
allows a user to click anywhere on the map interface and an elevation will be returned, in feet,
as well as the coordinates. The elevation profile tool will provide a cross section graph between
two points, in any direction.
The goal is to provide as much information as possible. Please contact us with
any suggestions or comments concerning SDDS and data.
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