6
G.A. Schultz and E.T. Engman
pIe extensions of photogrammetry. Remote sensing can produce an integrated
measurement that is simultaneously observing several factors. It is also giving us a
view that is uncommon to our past thinking in that it looks at a relatively large
area and somehow integrates information from the entire scene. A great deal of
research is needed to learn how to properly interpret the complex response obtained from the various remote sensing instruments. To use these data effectively,
we also must develop new concepts and change our historical way of conceptualizing hydrologic processes.
1.4 Satellite Systems
This book addresses the subject mostly from the perspective of satellite sensors
because these observations are almost universally available worldwide. Although
the choice of satellite orbit and design are beyond the scope of this book, a practicing hydrologist should understand the basics of sensors and orbits of the major
satellite systems because they can influence the choice of data. The existing satellite systems provide very good coverage of the Earth and give the hydrologist a
number of options for satisfying data needs. The choice of which satellite system
to use depends upon the requirements for the data, which translate into the need
for specific spectral bands, spatial requirements, temporal coverage, and the possible need for stereo coverage, all of which are related to the satellite platform.
Each of these is discussed more thoroughly below:
1.4.1 Remote Sensing Platforms
The choice of the remote sensing platform is also important to the hydrologist.
Platforms include ground based (usually truck or tower mounted), aircraft and the
space shuttle, in addition to the satellite systems.
Generally truck mounted and ground based systems are used for sensor development, investigating sensor-target interactions, and algorithm development.
These systems enable one to control very precisely what the sensor is "seeing".
Figure 1.1 is an example of truck mounted instruments being used for soil moisture experiments over a controlled target.
The aircraft and space shuttle provide an intermediate step before going to a satellite for further instrument and algorithm validation. Aircraft, however, also provide a very useful platform for coverage of relatively small areas and nonrepetitive
missions such as aerial photography, multispectral and thermal imaging missions
and side-looking airborne radar surveys. Figure 1.2 is the NASA C-130 that has
been used for many aircraft campaigns. This aircraft is essentially a flying laboratory and is designed to collect data from multiple instruments at any time.
The Space Shuttle (Fig. 1.3) is frequently used as a space borne platform for
proof of concept and testing of new instruments. The Shuttle Imaging Radar (SIRC) is a good example of this. SIR-C was a 1994 experiment with a two frequency
Synthetic Aperture Radar (SAR) for measuring a number of Earth science characteristics, including snow (see Chap. 11) and soil moisture (see Chap. 9).
G.A. Schultz and E.T. Engman
pIe extensions of photogrammetry. Remote sensing can produce an integrated
measurement that is simultaneously observing several factors. It is also giving us a
view that is uncommon to our past thinking in that it looks at a relatively large
area and somehow integrates information from the entire scene. A great deal of
research is needed to learn how to properly interpret the complex response obtained from the various remote sensing instruments. To use these data effectively,
we also must develop new concepts and change our historical way of conceptualizing hydrologic processes.
1.4 Satellite Systems
This book addresses the subject mostly from the perspective of satellite sensors
because these observations are almost universally available worldwide. Although
the choice of satellite orbit and design are beyond the scope of this book, a practicing hydrologist should understand the basics of sensors and orbits of the major
satellite systems because they can influence the choice of data. The existing satellite systems provide very good coverage of the Earth and give the hydrologist a
number of options for satisfying data needs. The choice of which satellite system
to use depends upon the requirements for the data, which translate into the need
for specific spectral bands, spatial requirements, temporal coverage, and the possible need for stereo coverage, all of which are related to the satellite platform.
Each of these is discussed more thoroughly below:
1.4.1 Remote Sensing Platforms
The choice of the remote sensing platform is also important to the hydrologist.
Platforms include ground based (usually truck or tower mounted), aircraft and the
space shuttle, in addition to the satellite systems.
Generally truck mounted and ground based systems are used for sensor development, investigating sensor-target interactions, and algorithm development.
These systems enable one to control very precisely what the sensor is "seeing".
Figure 1.1 is an example of truck mounted instruments being used for soil moisture experiments over a controlled target.
The aircraft and space shuttle provide an intermediate step before going to a satellite for further instrument and algorithm validation. Aircraft, however, also provide a very useful platform for coverage of relatively small areas and nonrepetitive
missions such as aerial photography, multispectral and thermal imaging missions
and side-looking airborne radar surveys. Figure 1.2 is the NASA C-130 that has
been used for many aircraft campaigns. This aircraft is essentially a flying laboratory and is designed to collect data from multiple instruments at any time.
The Space Shuttle (Fig. 1.3) is frequently used as a space borne platform for
proof of concept and testing of new instruments. The Shuttle Imaging Radar (SIRC) is a good example of this. SIR-C was a 1994 experiment with a two frequency
Synthetic Aperture Radar (SAR) for measuring a number of Earth science characteristics, including snow (see Chap. 11) and soil moisture (see Chap. 9).