40 
composition. It operates by responding to commands entered from local idei 
or remote terminals. It interprets these commands, performs the re- the 
quested processing, prompts for further information, or provides an were 
error message (Cullinane Corp., 1980). Among the several facilities verj 
offered by INTERACT is the EXECUTE facility, which provides a complete proc 
programming language (the Execute Command Language) for on-line program have 
development. Using INTERACT commands, the user can construct an exe- pail 
cutable series of instructions, called an EXECUTE (or EXEC) file. EXEC bad 
files are particularly useful for handling frequently-used functions 
involving data manipulation, and are commonly used to perform operating 
system functions for non-programming personnel. 
It i 
The EXEC file for operating on the Pennsylvania data base was set up as frai 
a major subset of the existing ORSER EXEC file. The user enters this the 
subset by responding "DATABASE" to the first prompt by the ORSER EXEC at l 
file. In response to the next prompt, the user indicates whether Land- Whi] 
sat data are to be retrieved by county, forest district, grid cell, °f t 
quadrangle area, or irregular polygon. The next prompt asks for the 
name, number, or coordinates of the specified area. Another prompt the 
requests the channel (band) numbers required and then whether the out 
put is to be put on tape or disc. At any stage the user can type 
"HELP" for further explanation. (An example session with the EXEC file 
is given in the Appendix. ) 
anni 
The result of this interaction is an active file which consists largely scr ; 
of JCL set up to execute the SUBDB program. The file can be listed, a v ” 
checked, and the job run, or the user can stay in the EXEC file and stat 
simply request that the job be run. Following job completion, the ] 
required data subset will be stored on the requested medium in ORSER RD cove 
format. Any of the ORSER programs can then be accessed through the tur j 
EXEC file to continue processing of the data. cre£ 
f roi 
7. DATA MANAGEMENT AND THE CONSTRUCTION OF ADDITIONAL DATA LAYERS 0CCl 
to c 
No provision has yet been made within the EXEC file for keeping track ag 
of subset data sets. It appears at this stage that infrequently-used 
small subsets made to disc should not be stored permanently, and large 1 
subsets should be stored on tapes cataloged through the ORSER tape 
library system (Turner et al., 1982). Provision for keeping track of can 
subset data within the EXEC file may have to be made in the future, furt 
however, as new layers of information are registered to the data base. 
One already-existing data layer is a Pennsylvania binary forest/non- ve ^ c 
forest mask which was developed by GSFC by classification from the wit! 
resampled data base (Williams et al., in manuscript). the 
teri 
Another data layer under construction is a mosaic of summer 1981 data, ec j t 
which will be registered to the data base. The western half mosaic g^ n( 
(UTM 17) is being constructed at JPL while the eastern half (UTM 18) as ( 
has been put together at ORSER. The latter required that ORSER obtain t 
the VICAR/IBIS software and additional mosaicking software modules from 
JPL. This software was successfully implemented in the first half of 
1982 at the PSU Computation Center and can now be accessed through the f° r£ 
ORSER EXEC file. dat£ 
P°l) 
The procedure used for constructing the 1981 mosaic was similar to that ava ^ 
used in constructing the data base, except that each scene was initially Mosl 
registered to data base control points rather than to ground control couj 
points. The eastern mosaic was constructed during June and July 1982 t 
at ORSER, following a week's training of ORSER personnel by Mr. Ron d uc j 
McLeod of JPL. After some minor errors in the JPL procedures were