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Titel |
Multifractal analysis of topography: a case study at the regional scale |
VerfasserIn |
E. Vidal Vázquez, R. García Moreno, A. Paz González, J. G. V. Miranda |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250028394
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Zusammenfassung |
Topography is one of the main soil formation factors and influences climate pattern at
different scales. The first objective of this study was to analyze the multifractal
characteristics of complex topography at the regional level in Galicia, NW Spain. A
second objective was to compare topography structural features as assessed by
multifractal and geostatistical analysis. The study data set consisted of 118,492
altitude point measurements on a square grid of 500 x 500 m. The total surface area
was estimated at 29,750 km2. The exploratory statistical analysis revealed that
the data set did not follow any well-known natural distribution, nor exhibited any
heteroscedacity of importance. Multifractal analysis was carried out using the moment
method. Remarkably good multifractal scaling was obtained when analyzing measures
constructed from altitude. Results show a rather good definition of both, singularity and
generalized dimension spectra. Values of capacity, information and correlation
dimensions were 2.00±00, 1.853±0.039 and 1.784±0.067, respectively. The singularity
spectrum showed a typical concave downward parabolic shape characterized by a wide
aperture and relatively small asymmetry. Moreover, the right branch of the singularity
spectrum was longer than the left branch, which is in accordance with predominance of
low altitudes at the regional level. The multifractal study demonstrates that the
spatial arrangement of the topography of Galicia can be quantified by the properties
of their singularity and generalized dimension spectra. Semivariogram analysis
showed that the studied altitude data set exhibits spatial dependence. The pattern
of spatial dependence of the experimental semivariogram was stationary at small
distances and non-stationary at longer distances, where it exhibited a large amount
of tendency. An exponential semivariogram model with no discontinuity at the
origin, i.e. without nugget effect, could be fitted to the experimental data until 60 km
distance. It was concluded that singularity and generalized dimension spectra are useful
for describing and comparing topography variability in Galicia. Topographical
maps are needed for data visualisation and also as an aid in data interpolation at the
regional scale, for example soil and climatic variables. Multifractal information
might be useful to determine the best interpolation procedure for mapping purposes. |
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