**2. GIS, DEMs and remotely sensed data in computer cartography: An overview**

Automatic mapping techniques are currently supported by tools with a high potential in the field of graphic representation of data such as GIS and by the use of remotely sensed data. Thematic maps produced with these methods show clear advantages, although some limits in the restitution of certain themes, in particular the geomorphological symbology, are evident.

They represent a digital geo-referenced and updatable database, i.e. a cartographic document with hyperlinks to the obtained results by the manipulation of remotely sensed data. This document can be also exportable to different platforms (handhelds PC, WebGIS) for a wide spectrum of applications.

Often the result is an analogical map that is not easily readable, both for the large amount of information, or for the great number of symbols associated with the different landforms.

In order to adapt this kind of data to a digital file, the original map must be converted in a vector format (points, poly-lines and polygons) using a Geographical Information System or

The use of the rich symbolism available in most GIS software, improve the graphic

Images acquired by remote sensing and image analysis techniques can bring a significant




**2. GIS, DEMs and remotely sensed data in computer cartography: An** 

Automatic mapping techniques are currently supported by tools with a high potential in the field of graphic representation of data such as GIS and by the use of remotely sensed data. Thematic maps produced with these methods show clear advantages, although some limits in the restitution of certain themes, in particular the geomorphological symbology, are

They represent a digital geo-referenced and updatable database, i.e. a cartographic document with hyperlinks to the obtained results by the manipulation of remotely sensed data. This document can be also exportable to different platforms (handhelds PC, WebGIS)

GIS software (Bocco et al., 2001; Gustavsson et al., 2006; Vitek et al., 1996).

rendering, but does not solve the problem of readability of the map.

contribution in improving the geomorphological mapping.

morphogenetic processes represented in the map.

values enable to identify the geometry of the landforms.


The main results of this approach are:

satellite images in a new, prospective view.

for a wide spectrum of applications.

**overview** 

evident.

These types of data have significant advantages over traditional methods because they: i) overlay broad areas in relatively short acquisition times; ii) have a better accuracy and precision of the measured data relative to traditional techniques; iii) are in a digital format and, therefore, are simple to elaborate for both research and application purposes; iv) can be easily updated allowing to examine the same areas at different periods and to evaluate both the possible morphological evolution and the kinetics of investigated processes.

For these reasons, research in the Earth Sciences and in geomorphology is integrating, or in some cases completely replacing, traditional techniques of acquisition of spatial information with these new tools (Schmidt & Andrew, 2005; Yongxin, 2007).

It is worth noting that the use of images and digital data, in addition to the advantages described above, opens the possibility to apply new techniques of analysis of physical variables responsible for morphogenetic processes. This being so, the spatial analysis in GIS and the most common systems of image analysis, represent a new field of Earth Sciences and not only a simple application of the theoretical traditional knowledge (Burrough & McDonnell, 1998). The huge potential offered by modern systems, allowing the simultaneous integration and analysis of a large number of spatial data by a variety of mathematical functions, investigate the spatial connections between variables and reveal new relationships and landscape evolution models (sensu Evans, 1972; Hengl & Reuter, 2009; Pike, 2000).

Two new kinds of data are particular useful for the production of geomorphological maps: DEMs and remotely sensed images.

A Digital Elevation Model (DEM) is the modelling of the Earth's surface or part of it in a digital format. Two types of DEMs exist: Triangulated Irregular Network (TIN) and Grid DEM. A TIN is a complex vector data resulting from the interpolation of a set of irregularly spaced points (Braun and Sambridge, 1997; Peucker et al., 1977; Sambridge et al., 1995; Tucker et al., 2001). A square-grid DEM is a raster data where the topography assessment is modeled in a "*gridded set of points in Cartesian space attributed with elevation values that describe the Earth's ground surface*" (Wilson, in press). Although grid DEMs show several disadvantages due to the regular spatial resolution, occasionally causing the inability to detect some topographic variations, or the impossibility of modelling particular landforms features (such stream meandering), they are used in most studies focusing on terrain analysis in geomorphological, hydrogeological (flood analysis) and environmental applications (Moore et al., 1991). Moreover, the remote sensing techniques produce new data models increasing the quality and spreading of these data. Because of these reasons grid DEMs are nowadays the most widely used in geological models requiring topographic assessment.

DEMs can be produced by different procedures (Nelson et al., 2009; Taramelli et al., 2008; Wilson, in press):

1. Vectorization of existing hard-copy topographic maps. Contour lines and spot height can be digitalized and converted in a vector format to be stored like polylines and points with location and altitude value. This procedure allows to obtain a DEM for each part of the Earth represented on a topographic map, but show several disadvantages. In particular, they are time consuming and the quality of the final product strictly depends on the original map and on the acquisition methods.

The Use of Remote Sensed Data and GIS to Produce

Regional Park. (1) Geosites, (2) Regional Parks.

a Digital Geomorphological Map of a Test Area in Central Italy 101

Fig. 1. Location map of the Umbria Region (central Italy). The white circle marks the Subasio

Fig. 2. Left: DEM of Subasio Mountain Regional Park with altitude values in meters a.s.l. Right: geological map. (1) Alluvial deposits, (2) Colluvial deposits; (3) Debris deposits (active); (4) Debris deposits (ancient); (5) Fluvial **L**acustrine complex; (6) Travertine; (7) Calcareous complex; (8) Terrigenous complex with prevalent clay percentage; (9)

Terrigenous complex with prevalent arenaceous percentage.


When, by transparency tools, satellite images or digital orthophotos (geological, geomorphological, land-cover e.g.) are overlaid as several thematic maps to a shaded relief, a composite visualization is achieved. In geomorphology DEMs are commonly used to calculate topographic attributes (Franklin, 1991; Moore et al., 1991; Pike, 1988; Wiebel & Heller, 1991). Among them, primary attributes are morphometric parameters deriving from DEMs, i.e. slope, aspect, plan and profile curvature. The visualization of topographic attributes and their analysis can be a very useful tool to better understand the geomorphological processes acting on a study area.

Remotely sensed imageries have a large improvement in both areal coverage and technical characteristics. Moreover, the selection of the most fitting band combination in RGB (Red, Green, and Blue) allows highlighting the required morphological characteristics and processes and facilitates landforms recognition.
