README  for data files included on this CD-ROM

 

 

****************************************************************************

These are image files of the various data layers, compressed with

gzip. The image files are binary raster files, with ENVI headers.

If a different header is needed for different software,

the image parameters are:

 

 

Number of Lines:  2910

Number of Samples: 4626

Number of Bands:   1

Upper left corner of Upper Left Pixel:  -2362000, 3178000

Pixel size 1000 m

 

 

Projection information:

 

 

          Albers Conical Equal Area Projection

          Datum NAD 83

          Spheroid  GRS1980

          Units Meters

          1st Standard Parallel              29  30  0.00

          2nd Standard Parallel              45  30  0.00

          Central meridian                  -96  0   0.00

          Latitude of projection's origin:   23  0   0.00

 

 

****************************************************************************

 

 

impervious_2001.tif      Image of estimates of percent development for

                         each pixel.

 

 

us_radiance_2001.tif     The Radiance Calibrated Lights product

                         for the coterminous United States.  DN

                         values can be converted to radiance with

                         the equation

                         Radiance = DN * 10^(-9) watts/cm^2/sr.         

 

 

roads_total.tif          Image of lenth of roads per 1 km-square pixel,

                         derived from streets and roads layers of Census

                         Bureau  TIGER 98 files. Pixel values are

                         sum lengths of streets and major roads (including

                         interstate highways) in units of meters.

 

 

 

 

 

 

nlcd_class#.tif          Image of land cover classification produced by the

                         USGS National Land Cover Characterization Project,

                         acquired from Landsat TM for years near 1992.

                         A more complete description can be obtained at

                         (http://landcover.usgs.gov/natlandcover.html).

 

 

                         The classification key (21 classes) can be obtained

                         at (http://landcover.usgs.gov/classes.html).

                    

                         Pixel values range from 0 to 10,000.  The percent

                         area estimate was multiplied by 100 to keep data

                         precision (e.g. 9876 means 98.76%).

                        

 

 

us_pop2000.tif           Population density image derived from Landscan

                         2000 Global Population Database, developed by

                         Oak Ridge National Laboratory. Pixel values are

                         population density per square kilometer.

********************************************************************************