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.