Geoscience Reference
In-Depth Information
- spatial resolution, which is measured in kilometers, does not allows us to
distinguish how drought affects one particular land use in comparison to another.
The analysis is, therefore, carried out on a range of different crops. This means that
it is not possible to specify which type of vegetation is affected the most by drought;
- a second point to be taken into consideration includes time delays, which occur
as a the result of pre-processing methods used to produce the images. A monthly
analysis of the NDVI will include index values recorded at the beginning of the
month; yet during the entire period when the images were taken these values were
steadily decreasing. There is a lack of precision during the analysis phase, especially
from a spatial and temporal viewpoint. The use of medium resolution daily images
(similar to MODIS type data) would limit the effects of such time delays and would
limit the effects of using such a wide range of pixels.
3.5. Conclusion
The importance of using satellites in climatology and meteorology goes beyond
the scope of research activities. Their usefulness no longer needs to be proved in
numerous economic activities (agriculture, fishing, etc). The monitoring and
forecasting of meteorological conditions (the cause of 20% of all road accidents in
France) shape our daily lives, and the images produced by meteorological satellites
are broadcast to the general public (it is impossible to have a televised weather
update without the use of satellite animation). Satellite images produced by
meteorological satellites are created every day [BAD 95; RAI 03]. Climatologists
have a phenomenal amount of diverse information at their disposal. Our atmosphere
is continually examined at many levels and there is a considerable amount of tools
available to help climatologists carry out this task. A better understanding of the
atmosphere will lead to models carrying out better weather forecasts in the future. A
proper understanding of the different variables that affect climate makes it possible
to slightly alter economic activity, to make slight alterations to buildings, etc. In
addition, it informs people about what clothing they should wear on a particular day.
In this respect, the climate is at the center of our everyday concerns, and strongly
contributes to the characterization of a particular geographical area.
Satellite images have turned out to be fantastic tools used to spatialize
geographical information that relates to climate. Homogenous spatial resolution and
the repetitiveness of satellite data are precious tools that can be used to create
detailed maps. New sensor programs should make it possible to increase spatial,
spectral and temporal resolutions. The widespread use of GIS makes it possible to
integrate satellite products as one of the entry layers in a GIS. Such an entry layer is
necessary for providing spatial information about a particular piece of data. There
are two important key elements to be remembered here: the satellite measurement is
not equivalent to any measurement taken on the ground but merely provides extra
and complementary information about it. Second, when carrying out any satellite
measurements certain methodological precautions need to be adhered to
(radiometric calibrations, geometric and atmospheric corrections). It should be noted
that measuring surface conditions depends on cloud cover as far as visible light and
