17 Irrigation and Drainage
395
detailed information on missions and satellites for earth observation the reader is
referred to Kramer (1994). Because of the fast pace of changes in the IEOS
satellite missions the information provided by this otherwise very valuable book is
at times incomplete or outdated. Updates can be retrieved from the home pages set
up for most missions and sensor systems. At least two consequences of technological evolution should be mentioned in the context of this chapter:
users should be rather knowledgeable to choose the best observational approach
given the complexity and diversity of available options.
Developing countries have an increasing and active role in the development of
earth observation from space.
Technological evolution has been relatively limited during the first two decennia
of earth observation. A useful improvement in the most recent ones of the current
sensors (e.g. MOS) is the better spectral sampling in the region where useful
spectral features related to green biomass may be detected. The low spatial
resolution, however, restricts the potential use of such observations to large-area
surveys.
The comparison of the characteristics of the current spaceborne sensors with the
characteristics of the advanced airborne sensors shows immediately that major
technological developments were taking place at the same time as practical
approaches were being developed on the basis of simpler measurements. The
number of imaging spectrometers, for example, is increasing very rapidly and
many comparable sensors are available for field studies. To a large extent this is
due to the availability and rapidly decreasing cost of solid state arrays of detectors.
Smaller countries and industry have developed such systems, at times with
commercial applications in sight. Spectrometry from space at intermediate
resolutions will be a reality soon (MODIS, 1999, while true spectrometers at high
resolution will come later (PRISM, 2003). It should be noted, however, that hyperspectral observations at high spatial resolution might have been available already,
had not the LEWIS mission failed in 1997.
We are past the time of generic remote sensing applications and specific
approaches (i.e. based on well identified measurements) should be developed.
Technological evolution may contribute to improve significantly the timeliness of
observations. Light but powerful instruments may be flown on unconventional
platforms such as ultra-light aircrafts at a cost attractive to true end users, such as
farmers in a competitive agriculture or operators of advanced on-demand irrigation
systems.
17.5 Future Directions and Potential
Irrigation and Drainage, as an area of research and application, has been a fruitful
learning and development ground for a broad range of remote sensing applications.
Several inherent features of irrigated lands led to this situation. Irrigated lands are
generally flat or gently sloping, the contrast between irrigated and non-irrigated
areas is significant especially in arid and semi-arid zones, serious water
395
detailed information on missions and satellites for earth observation the reader is
referred to Kramer (1994). Because of the fast pace of changes in the IEOS
satellite missions the information provided by this otherwise very valuable book is
at times incomplete or outdated. Updates can be retrieved from the home pages set
up for most missions and sensor systems. At least two consequences of technological evolution should be mentioned in the context of this chapter:
users should be rather knowledgeable to choose the best observational approach
given the complexity and diversity of available options.
Developing countries have an increasing and active role in the development of
earth observation from space.
Technological evolution has been relatively limited during the first two decennia
of earth observation. A useful improvement in the most recent ones of the current
sensors (e.g. MOS) is the better spectral sampling in the region where useful
spectral features related to green biomass may be detected. The low spatial
resolution, however, restricts the potential use of such observations to large-area
surveys.
The comparison of the characteristics of the current spaceborne sensors with the
characteristics of the advanced airborne sensors shows immediately that major
technological developments were taking place at the same time as practical
approaches were being developed on the basis of simpler measurements. The
number of imaging spectrometers, for example, is increasing very rapidly and
many comparable sensors are available for field studies. To a large extent this is
due to the availability and rapidly decreasing cost of solid state arrays of detectors.
Smaller countries and industry have developed such systems, at times with
commercial applications in sight. Spectrometry from space at intermediate
resolutions will be a reality soon (MODIS, 1999, while true spectrometers at high
resolution will come later (PRISM, 2003). It should be noted, however, that hyperspectral observations at high spatial resolution might have been available already,
had not the LEWIS mission failed in 1997.
We are past the time of generic remote sensing applications and specific
approaches (i.e. based on well identified measurements) should be developed.
Technological evolution may contribute to improve significantly the timeliness of
observations. Light but powerful instruments may be flown on unconventional
platforms such as ultra-light aircrafts at a cost attractive to true end users, such as
farmers in a competitive agriculture or operators of advanced on-demand irrigation
systems.
17.5 Future Directions and Potential
Irrigation and Drainage, as an area of research and application, has been a fruitful
learning and development ground for a broad range of remote sensing applications.
Several inherent features of irrigated lands led to this situation. Irrigated lands are
generally flat or gently sloping, the contrast between irrigated and non-irrigated
areas is significant especially in arid and semi-arid zones, serious water