Author/Editor		Delclaux, Francois; Depraetere, Christian
Title		Methodological approach for hydrological landscape definition: application of texture measures on west African watersheds
Type		članek
Source		Image Anal Stereol
Vol. and No.		Letnik 20, št. Suppl 1
Publication year		2001
Volume		str. 590-5
Language		eng
Abstract		A method for estimating the homogeneity level of hydrological spatial units is presented here. The approach is based on (i) the quantification of homogeneity by using specific indices, (ii) the influence of the spatial data error on homogeneity. Texture metrics, based on the co-occurrence probability matrix and dedicated to homogeneity quantification, are investigated. The sensitivity of these texture metrics, considered as homogeneity indices, is assessed in two types of landscapes: virtual landscapes characterised by elevation, and watersheds characterised by the relief curvature. The calculation of homogeneity indices reveals considerable variation in the way the spatial homogeneity is perceived. Three groups of indices are then fonned by applying the principal components method and clustering analysis, each group being characterised by one index: contagion, contrast and Angular Second Moment or Inverse Difference Moment. In the second part of this paper, the influence of the data quality is analysed. The spatial error propagation is modelled using a stochastic simulation in the watershed dataset framework: a set of random elevation surfaces is generated using a Monte-Carlo method from which the corresponding curvature fields are derived. Next, homogeneity index samples are obtained for each watershed. The result shows a global decrease in homogeneity depending on the value of the elevation error and the type of index.
Descriptors		GEOGRAPHY FRESH WATER IMAGE PROCESSING, COMPUTER-ASSISTED AFRICA, WESTERN