potential for calculating a variety of lake surface charac 
teristics from computer-compatible Landsat data. 
Updating Lake File Information (Program UPLAKE) 
The master lake file test area was updated with additional 
information for 3 lakes within the quadrangle specified for 
retrieval. These lakes were named SLAR-1, 2 and 3 (Mellor 
1982). The updating procedure added information from other 
sources to the file (e.g. lake name, maximum depth, area of 
free water below ice, fish, vegetation, conductivity, etc.). 
Tables 1 and 2 illustrate the difference between computer 
retrievals from the file before and after updating. 
Retrieval System 
Limited space here permits only one type of lake retrieval 
request (Tables 1 and 2) to illustrate the retrieval system 
capabilities. Computer listings of lakes on file can be 
generated by requesting a catalog of all lakes or by selec 
tive retrieval of lakes within a specified geographic quad 
rangle and/or of lakes fitting specified characteristics. 
Tables 1 and 2 provide examples of computer listings re 
trieved from a user defined quadrangle and by selectively 
filtering the file by the lake surface area parameter only. 
A quadrangle, that includes SLAR-1, 2 and 3 lakes, rep 
resenting about 1% of the total area within the scene was 
identified for retrieval. This quadrangle is about 286 km^ 
and is shown in Figures 1, 2, and 3 relative to the 1,370 
km^ area that was processed to create the lake file. This 
quadrangle was chosen primarily because of the verification 
data that existed for SLAR-1, 2, and 3 lakes, but the area 
is representative of the Arctic Coastal Plain and contains 
riverine, as well, as lacustrine and palustrine environ 
ments . 
Catalog. An example of catalog retrieval is not included 
here, because all 1,426 lakes on the master file would have 
been listed after being sorted by one of the following: 
latitude and longitude, maximum depth, computer calculated 
surface area, free water area beneath ice, % vegetation 
cover, conductivity, or name. 
Geographic Quadrangle. A geographic quadrangle was 
identified to limit consideration of the 1,426 water bodies 
in the file to a specific area of interest by requesting the 
latitude and longitude of the northeast and southwest 
corners in degrees and minutes accurate to 1 decimal place. 
The subroutine ARCALC calculates the area defined and prints 
the area at the end of requested output as the "user defined 
geographic area" (Tables 1 and 2). The computer-calculated 
area was 285.61442 km^. During a retrieval run not illus 
trated here, the quadrangle was specified with no further 
lake filtering parameters. This request listed and summed 
all water bodies within the 285.6 km^ area. The listing is 
not included here because of its size, but 252 water bodies 
with a combined area of 43 km^ were listed as present within 
the Figure 2 parallelogram. The percentage of water over 
this terrestrial estate was 15% of the total land area as 
calculated from this computer-generated listing.