Abstract
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.
Highlights
The Digital Terrain Model is a representation of continuous elevation values over a topographic surface by a regular array of z-values [1] [2], referenced to a common datum
GPS measurements projected in Universal Transverse Mercator (UTM) system corresponding to ellipsoidal elevation and referred to as World Geoditic System (WGS 84) were converted into horthometric elevation [19]
The comparative study between GPS data and Shuttle Radar Topography Mission (SRTM), ASTER GDEM emphasizes an underestimation of the DTMs elevation value as shown in the table below (Table 1)
Summary
The Digital Terrain Model is a representation of continuous elevation values over a topographic surface by a regular array of z-values [1] [2], referenced to a common datum. The generation of DTMs can be achieved through two main methods [3]: either a direct collection of field data “direct survey” (e.g. topographical survey by GPS or total station) or remote sensing (e.g. LIDAR and RADAR). The generation of the last two techniques is carried out following a four-step process [11]: source of elevation data; resampling to required grid spacing; interpolation to extract height of required point and DEM representation, editing and accuracy assessment. Each of these steps might be a source of errors [12]. According to [13] errors can be classified into gross errors, systematic errors, and random errors
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