digital imagery and cartographic information 
in cassettes. It would allow the viewing of 
4 x 10° spatial elements. The user would enter 
into a computer a code for scene coordinates, 
perspective, desired scale, etc., and get a spa- 
tial picture. 
Pooled minicomputer systems 
The concept of pooled minicomputer sys- 
tems (Olsen, 1975) is under development by 
the Department of Defense with the collabora- 
tion of the U.S. Geological Survey. Special- 
purpose control computers on available analy- 
tical stereoplotters are being replaced by gene- 
ral-purpose minicomputers to provide signifi- 
cant flexibility for adding hardware and soft- 
ware modifications. Then the modified analy- 
tical plotters are connected to a central mini- 
computer in a distributive network so that the 
versatility of the total photogrammetric system 
can be significantly increased. 
This approach has been adopted in anticipa- 
tion of the increased digital-data collection for 
automated mapping. Instead of adding a CRT 
display and a disk storage unit to each analyti- 
cal plotter, it is more economical to install poo- 
led system with a distributive computer net- 
work, in which multiple computers are con- 
nected to each other and can mutually commu- 
nicate with one another. The AS-11B-1 was 
modified by connecting it to a MODCOMP 
11/25 minicomputer and adding a teletype 
and two cartridge disks as peripherals. The cen- 
tral minicomputer system is a MODCOMP 
11/45 with a full complement of peripherals, 
including Teletronix 4010 CRT display, disk 
packs, disk cartridges, magnetic tape, card 
punch, paper tape, line printer, and teletype. 
In the pooled system, each individual stereo- 
plotter will collect digital data much as if it 
were an independent system. Instead of being 
recorded directly on magnetic tape, the data 
will be stored on a cartridge disk an buffered 
until transferred to the central computer. Once 
the data are in the central computer, the large 
disk and the computer will serve a cataloging 
function as the data are reordered, gathered to- 
gether, and output on magnetic tape. 
U.S. Geological Survey 
Digital photogrammetry 
With the 
of Defense 
of 
USGS 
the 
has 
assistance 
(DoD), 
Department 
carried out 
a pilot project in digitization - deriving di- 
gital map data from the stereomodel and gene- 
rating graphics from the data. The AS-11B-1 
analytical plotter was used to extract digital 
planimetric and terrain data from unconventio- 
nal source material. An interactive editing sys- 
tem was used to smooth and plot the data. The 
two AS-11A analytical stereoplotters at USGS 
are being updated with minicomputers, and 
new analytical plotters are being obtained. An 
analytical stereocomparator with minicompu- 
ter, precision automatic plotters, a general-pur- 
pose computer, and automatic photoprocessors 
are also being acquired. 
Contour compilation from high-altitude 
photographs 
UNAMACE - generated contours derived 
from high-altitude photographs were tested, 
and indications are that they would probably 
meet National Map Accuracy Standards for 
mapping at 40-ft contour interval. However, 
lack of topographic expression due to loss of cor- 
relation is evident; 140 correlation losses oc- 
curred over half the quadrangle area. 
Use of pocket calculators 
Programable pocket calculators are being ap- 
plied to orientation of independent models on 
the Wild A7 and Kern PG 2. With camera- 
orientation data from aerotriangulation, the 
calculator is programed to compute 38 settings 
for relative and absolute orientation. 
Lens-distortion correction 
An improved method for correcting camera- 
lens distortion is based on grid intersections ra- 
ther than radial distances from the point of 
autocollimation. The new method permits digi- 
tal corrections for asymmetric and irregular 
distortion as well as for nonflatness of the ma- 
gazine platen. 
Image correlation 
(a) A study of density factors causing diffi- 
culties in automatic correlation was completed. 
Density traces (from a microdensitometer) were 
mathematically and visually compared. The re- 
sults indicate that among the factors causing 
correlation losses are : 
€ Objects appearing in only one photo 
€ Large objects obscuring small objects in 
one photo