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This paper focuses on the quality of the vertical accuracy of two Digital Elevation Models, corresponding to Kasserine region, central west Tunisia. The vertical accuracy assessment is based on 23 GPS ground control points belonging to the study area. We applied a statistic analysis approach and established 3 elevation profiles corresponding to GPS, ASTER and SRTM. The erected statistical analysis reveals that the Root Mean Squared Error (RMSE) was 8.88 and 10.13 respectively for SRTM and ASTER DTMs. 2D elevation profiles constructed for GPS measurements, ASTER and SRTM, highlight that both DTMs underestimate the true elevation and that SRTM DTM is quite closer to the GPS elevation profile. Relying on this investigation, we think that both DTMs are significant for the vertical accuracy assessment and we urge that SRTM DTM might scheme the Kasserine area features better than ASTER DTM.

The present work tests the use of hypsometric integral (HI) in identifying neotectonic and lithology signals in the Utica-Mateur basin (northeastern Tunisia), a region recognized by low deformation rates. We computed HI values using three digital elevation models (DEMs) of 10, 30 and 90 m pixel resolution.We extracted maximum, minimum, and mean elevations from each DEM. The obtained results reveal that the HI spatial distributions did not demonstrate clear spatial patterns and did not correlate with geological substrates. We also find that the distribution of HI is independent of the DEM resolution, butare influenced by the size of the moving window.By applying the hotspot analysis (Gi*-statistics) on extracted HI data, we find two main clusters with high (hotspots) and low (cold spots) HI values. These hotspots correspond mainly to active faults and coincide with shallow earthquake clusters in the study area. IntroductionHypsometry describes area distribution at different elevations (Strahler 1952)and can be estimated using the hypsometric curve (HC) and the hypsometric integral (HI). The HC was developed by Strahler (1952)to infer the temporal stages of geomorphic development of watersheds. This curve is classically obtained by plotting the proportion of the total basin height (i.e. relative height) against the proportion of total basin area (i.e. relative area). It can also be displayed in non-dimensional form, allowing direct comparison of watersheds, irrespective of scale issues. The HI was defined as the area under the HC (Strahler 1952), and it has been used to investigate the Downloaded by [La Trobe University] at 02:17 01 June 2016 4 geomorphological stage of a basin. The HI can be estimated by means of the following equation ( Pike &Wilson 1971): elevation) minimum -elevation (maximum elevation) minimum -elevation (mean = HI (1) Strahler (1952) proposed three geomorphic stages to explain the distinctive series of hypsometric curves. Based on the hypsometric curves shapes, he classified drainage basins as following: (1) convex hypsometric curves with HI above 0.6 are typical of youthful stage, (2) S-shaped hypsometric curves with HI in the range 0.35 to 0.6 are related to maturity stage, and (3) concave hypsometric curves with HI below 0.35 are indicative of Monadnock stage. This classification was adopted by many researchers as an estimator of erosion status of watershed leading to prioritization of watershed for soil and water conservation measures(Singh et al. 2008).