Geoscience Reference
In-Depth Information
proportional to the accuracy of the information used to produce them. What really
happens? Does this so-called loss in quality (associated with large-scale resolutions)
occur to the same extent for the interpolation of both average and daily data? This
raises the issue of spatial-temporal scales, which are an integral part of interpolation.
- There is also the issue of the selection of independent variables, which must be
quantitative this is the case for digital elevation models (DEM). However, as far as
land cover is concerned (when using Colrine land cover (CLC), how is it possible to
do with the technique of interpolation when the only variables that are available are
qualitative?
- The choice of interpolation method to be used depends on numerous factors,
such as the type of variables to be interpolated, the information that is available, etc.
A brief overview of all the different interpolation methods will be given in this
chapter, with the help of specific examples. Unfortunately, however, our research
will be unable to provide a miraculous solution to those climatologists and
geographers who want to use a specific interpolation method, but it will help them
choose a particular method so that they can continue to carry on with their own
research or work.
All of the issues raised here are based on new processes that were developed
from data recorded and published by Météo-France. The data collected related to
rainfall, temperature, and duration of sunshine in mainland France.
2.2. Geographic information necessary for interpolation
It is not possible to represent information on a map if nothing is known about
the location of the measurement stations, or if there is no information available
about the data that is to be represented. The third important element that also needs
to be taken into consideration refers to information that exists outside the world of
climatology and which is used as a support to spatial analysis.
2.2.1.
The location of the measuring sites
It is possible to find out the exact location of each weather station on the Earth's
surface due to the geographic co-ordinates that make-up the geometric aspect of a
GIS. Until the middle of the 1990s it was only possible to work out the location of
such climatological stations by using topographic maps. Measurements taken from
the stations tended to be full of errors. A well-trained geographer is able to locate a
meteorological station on a topographic map to the nearest millimeter, which
translates as being 50 m on a map with a scale of 1:50,000 or 25 m on a map with a
scale of 1:25,000.
Such methods for working out the locations of weather systems have been
replaced by GPS systems. Even if the potential margin for error has decreased, it
should be highlighted that the inaccuracy of a measurement can be approximately
