1_README.TXT

UNGA GEOPHYSICAL DATA SET
ERMAPPER(1) FILES

The files contained in this subdirectory have been used to 
construct images for the airborne geophysical data of Unga 
Island.  Popov island data were not included in the project 
reports and are not included as ERMAPPER files. 

ERMAPPER is a commercial program that is used for geographic 
information system purposes.  Processing of geophysical data 
is also an application.  The version used in this project is 
5.5a implemented for both a personal computer and a UNIX 
system.  More complete information about the software can be 
found on the Web site:  http//:www.ermapper.com.  A free 
viewer for ERMAPPER files can be downloaded from that Web 
site.

The following is a brief description of the files in this 
subdirectory.  Files ending in "alg" are algorithm files that 
are used to assemble data files (see below) into an image. 
These files, "Figure*.alg", can be used to recreate the 
figures given in the geophysical chapter of this report. 
Files with an "erv" extension are header files for vector 
data sets.  The data set corresponding to the "erv" file have 
the same file name but no extension.  For example the files 
BRFaut and BRFault.erv are a pair.  Files with an "ers" 
extension are header files for raster geophysical data sets 
(same name without extension) such as the total field 
magnetics.  The main raster data file, Unga_MDS, contains all 
of the digital data sets as separate "bands".  For example 
one band is total field magnetics, another band is the 900 Hz 
apparent resistivity, and so on. 


(1)trademark of Earth Resources Mapping; Use of trade names 
by the U.S. Geological Survey does not directly or indirectly 
imply endorsement.