Imagery

The public may download digital aerial photography products at no cost from the Earth Resources Observation and Science Center (EROS).
No. A photographic enlargement only appears to show more detail than a 9-by-9 inch photograph. Photographic resolution (or image resolution) deteriorates with each enlargement factor.
Aerial photographs and satellite imagery for the United States are available in many formats as described on the EROS Web site:
Landsat 8 carries two push-broom instruments: the Operational Land Imager (OLI), and the Thermal Infrared Sensor (TIRS).
It will probably take approximately 5 years to digitize the archive. A priority scheme is being developed and will be made available to the public at a later date.
A USGS DRG is a scanned image of a U.S. Geological Survey (USGS) topographic map. The term refers to products created in the period 1995-2000 that conform to a specific technical standard.
SDTS transfers are the data sets used to exchange spatial data between different computer systems.
Digital Line Graphs (DLG) are an early GIS vector data product. The product line has been inactive since the mid 1990s, and has been superceded by more modern GIS datasets.