EM 1110-2-2907
1 October 2003
Chapter 3
Sensors and Systems
3-1 Introduction. Remotely sensed data are collected by a myriad of satellite and air-
borne systems. A general understanding of the sensors and the platforms they operate on
will help in determining the most appropriate data set to choose for any project. This
chapter reviews the nine business practice areas in USACE Civil Works and examines
the leading questions to be addressed before the initiation of a remote sensing project.
Airborne and satellite sensor systems are presented along with operational details such as
flight path/orbits, swath widths, acquisition, and post processing options. Ground-based
remote sensing GPR (Ground Penetrating Radar) is also introduced. This chapter con-
cludes with a summary of remote sensing and GIS matches for each of the nine civil
works business practice areas.
motely sensed imagery was confined by system constraints and only provided by a few
vendors. Imagery that was available from archive, or that would become available due to
orbital frequency, maintained numerous constraints; consequently ground coverage,
rather than image resolution, was the primary concern. Additionally, minor consideration
was given to the spectral characteristics of the target and the spectral bands available, as
there were a limited number of imaging platforms. To an extent projects had to be tai-
lored to fit the limitations of the data. This is no longer the case however, with signifi-
cant technologic improvements and numerous product choices. Creative researchers are
finding new applications in the on-going advancement of remote sensing.
b. Image Improvements. Satellite sensor system developers continue to improve im-
age cost, resolution, spectral band choices, spectral data library sets, and value-added
products or post-processing methods. Improvements in sensor development and afforda-
bility can be attributed to the commercialization and subsequent expansion of the remote
sensing industry. NASA, other US governmental agencies, and foreign space agencies,
such as those in Canada, France, India, and Japan, progressively enhance the industry by
furthering current technologic advances in the remote sensing field. Consequently, the
resolution constraints on data that existed 20 or more years ago are no longer an obstacle
with the addition of these affordable higher resolution systems. Listed here are just a few
examples of airborne and satellite data costs:
AVHRR scene at 1 km GSD for <
Landsat TM scene at 30 m GSD for 5
Landsat ETM scene can be acquired for 0
ERS-1 SAR scene at 25 m GSD for 00
ERS-2 SAR scene at 25 m GSD for 00.
Vendors of high-resolution satellite imaging systems products (such as
IKONOS or QUICKBIRD or other products with <4 m GSD [ground sampling distance
is the spatial resolution measurement]) charge on a per area basis. The minimum area is
11 km2 for approximately 00.
3-1
Previous Page
