Thus, an understanding of the complex rela- 
tionships between energy and matter can per- 
mit one to select a remote sensing system for 
reconnaissance which gathers a maximum 
amount of information within the environmen- 
tal constraints placed upon it. (For a more de- 
tailed review of basic matter-energy relation- 
ships, see Colwell, et al. 1963.) 
REMOTE SENSING CARRIER VEHICLES 
AND DEVICES 
Remote sensing began its evolution about 
1858, when the first aerial photograph was 
taken by a camera carried aloft in a gas-filled 
balloon. Since then, the dirigible, airplane, 
helicopter, and rocket have carried cameras 
and other remote sensing devices to obtain 
photographs and photo-like images from a 
vantage point above the terrain. The data se- 
cured by such systems have been used widely 
for various military and resource applications. 
In recent years, photos obtained from manned 
and unmanned orbiting satellites have demon- 
strated the potentialities for remote sensing. 
For example, NASA’s Earth Resources Survey 
Program was established more than 4 years 
ago to explore the feasibility of developing re- 
mote sensing systems for inventorying earth 
resources from space. This program has stimu- 
lated scientists to evaluate all remote sensing 
devices capable of operating from spacecraft 
and/or conventional aircraft, and to determine 
which devices are useful for improving inven- 
tories for the various resource disciplines (e.g., 
agriculture, forestry, range, geology, hydrol- 
ogy, oceanography, geography). 
Once the informational requirements have 
been defined, consideration may then be given 
to a remote sensing system which permits pro- 
curement of data from which interpretations 
and measurements can yield solutions to re- 
source problems. The information derived from 
a single remote sensing system in many cases 
can be used to satisfy a number of different in- 
formational requirements of the range or wild- 
life manager. 
Many kinds of remote sensing devices are 
available for recording information in specific 
energy bands of the electromagnetic spectrum. 
Six types of remote sensing equipment show 
the most promise for inventorying natural re- 
sources (Colwell 1968) : 
(1) The conventional single-lens aerial cam- 
era. This sensor has a fixed-lens assembly of 
specified focal length. It collects reflected ra- 
diation in the visible and near infrared bands 
on various kinds and formats of film. Because 
of the fixed geometry of this system, the resul- 
tant photograph provides an ideal map base. 
(2) The panoramic camera has a movable 
lens that pivots from a fixed point through an 
are and exposes a wide photo swath of the ter- 
rain below (perpendicular to the flight line) on 
a 70-mm. black-and-white or color film emul- 
sion. The panoramic photographs vary in scale 
from the outer edge into the center of the 
photo, so although this camera generally is not 
used for mapping purposes, it can obtain high 
resolution photographs. 
(3) The multiband or multilens camera is a 
camera assembly with two or more lenses. By 
using various filters, several specific bands of 
energy in the visible or near infrared spectrum 
can be simultaneously sensed and recorded on 
film. In some instances several film types are 
exposed simultaneously through a multilens 
camera. 
(4) The optical mechanical scanner can re- 
cord energy responses in the ultraviolet, visi- 
ble, near infrared, and far infrared bands 
simultaneously by using a variety of detectors 
sensitive to radiation of different wavelengths. 
Unlike a camera, the scanner focuses reflected 
and emitted radiation through mirrors onto 
sensitized detectors by means of a rotating 
prism. The energy response received by the 
detectors (photo multiplier tubes for the visi- 
ble and near infrared and solid state semicon- 
ductors for the thermal infrared), is converted 
into electrical impulses, which are either re- 
corded on magnetic tape or are converted by 
means of a cathode ray tube into a series of 
line scans that form a continuous photo-like 
image of the terrain below. (The term “imag- 
ery” refers to the photo-like presentation of 
line sean data.) 
(5) Side-looking radar is an active all- 
weather sensing system that generates its own 
long-wave radiation, transmitting it to the ter- 
rain below. The returning radar impulses are 
received via an antenna and_ transformed 
through several steps into photo-like images, 
usually in the form of contiguous line scans. 
(6) The gamma ray spectrometer, which can 
only operate at a short distance above the ter- 
rain (due to atmospheric absorption) to record 
gamma rays emitted from radioactive mate- 
rials. Very little application of the gamma ray 
spectrometer is expected in range environ- 
ments, except for mineral exploration. 
A brief description of the operating charac- 
teristics of these sensing devices is given by 
Colwell (1968). 
Cameras, Films, and Filters 
Much of the early panchromatic photogra- 
phy was obtained with a T-11 mapping camera 
and a K-17 reconnaissance camera. Both meet 
the minimum standards for mapping vegeta- 
tion and soil; hence, they have been greatly 
used for this important application. The types 
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