**Contribution of New Sensors to Cartography**

Carla Bernadete Madureira Cruz and Rafael Silva de Barros

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/48258

**1. Introduction** 

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Different cartographic representations are considered fundamental for the Geographic Science, whose characteristics are related, almost always, with the need for representation and analysis of spatially distributed phenomena. Therefore, it is fundamental that the cartographic bases are available, meeting the needs regarding the accuracy and updating, in different scales.

Generation and maintenance of these bases are considered as highly complex, considering all the planialtimetric information that they should contain, mainly in the case of a large country as Brazil, whose territory extends for about 8.5 million km², with many areas of difficult access. Furthermore, there is a need for concern also with the thematic maps, whose origins depend on the cartographic bases themselves, which operate as spatial reference, besides other inputs originated normally from field surveys and remote sensing. The diversity of these maps is enormous, creating an immense variety of methods and specialists involved in their preparation.

With all this progress, cartography is presenting growing changes in the form of preparation and divulging of its products. The availability of new technologies, for acquisition, storage and dissemination of spatial data, made the use of maps and images increasingly popular, reaching not only government organizations and private companies, as habitual, but also individual users. On the other hand, this same technological progress has entailed a new context of methodological solutions, some of which presenting themselves as interesting alternatives for the process of maps generation, despite presenting also many future challenges. Changes to the way work is carried out are fundamental to attend viable solutions in ongoing applications, in the long-term, that also require a high level of quality, as those involving systematic cartography.

It is a fact that the consolidation of the Information Technology in practically all areas of knowledge, with the consequent cost reduction regarding software and hardware, was

© 2012 Madureira Cruz and Silva de Barros, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Madureira Cruz and Silva de Barros, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

fundamental in this evolutionary process. Despite the intense and growing offer of technologies, the adsorption of the new methods and products, which were slowly converted from analog to digital, involves countless challenges, being slower than expected or desired. It should be highlighted also that the conversion requires the review of many concepts that need to be adapted to the new reality, as in the case of the sheets of charts in a certain scale in view of the challenge of preparation of continuous bases.

Contribution of New Sensors to Cartography 183

products derived from remote sensing images may end up presenting a lower quality than desired, for, among other reasons, generating an expectation of intrinsic good quality. This may occur for being considered something modern, conveying the impression that the leading-edge technology is synonymous of - or is very near to present - guaranteed quality. In an opposite vision of the former, it is noted that there is a group of users who reveal suspicion or misbelief regarding the promised potentialities. Probably this occurs for different reasons, such as insufficient information, prejudice, or still, concerns with loss of jobs. Such resistances delay the renewal of methods and techniques, ending up to configure "pre-judgments" that end up making the performance of an analysis difficult, even in an emergency character, regarding their real efficacy. The results of our studies offer greater clarifications on products originated from different sensors, leading the reader to the need to break myths - pessimistic or optimistic -

It is important also to consider that during recent years a lot of investment was carried out in new sensors, aiming to meet different applications. It is in place to state that we are being overrun by growing offers of novelties associated to many promises. The universe of remote sensors aimed at terrestrial studies is therefore very wide, involving products with several and variable spatial, radiometric, spectral and temporal resolutions. Such diversity allows the production of mappings with different detail and accuracy levels, of greater or minor

Another relevant consideration is the fact that many sensors allow also the extraction of 3-D data, also with different resolutions and accuracy levels. One fundamental mark in this area is undoubtedly SRTM (Shuttle Radar Topography Mission), which despite not having been the pioneer, is the most encompassing and popular Digital Elevation Model (DEM) available worldwide. Consequently, there is a growing need to study the quality of the altimetry obtained from such sensors, and also an assessment of how much the implemented advances in the data acquisition process can influence the results, as for instance the along-

A differentiation between DEM and Digital Terrain Models (DTM) can be useful, because often this is one of the arguments against the use of orbital images for the generation of terrain representations. In a simplified way, it will be assumed that the DEMs represent the land surface added by any existent objects on it and which influence the value of the pixel reflectance. In other words if there are trees and constructions, the surface represented refers

Despite so many investments in orbital sensors, the airborne surveys still offer greater accuracy for their products. It is emphasized also that there are some benefits of the active sensors in relation to passive sensors, as the case of the interferometer radar and LIDAR (LIght Detection And Ranging), which are not subject to atmospheric interferences and allow extraction of DEMs

In the case of new methodologies for generation of DEM/DTM to meet the expectations, reaching greater detail scales, an important step was taken in the sense of generating data with a good cost/benefit relation, mainly regarding time reduction, if compared with

to the top of them. The DTMs on the other hand, represent the actual ground surface.

and DTMs - depending on the band for radar and the density of points for LIDAR.

regarding the use of remote sensing, mainly at orbital level for cartographic ends.

complexity of legend and the possibility to follow up dynamic phenomena.

track stereoscopy (images acquired during satellite orbit) and interferometry.

Therefore, an interesting new panorama is configured, which presents a diversity of uses with a growing demand for Geographic Information, associated, increasingly, with the use of Geographic Information Systems and products originated from Remote Sensing. The lack of control of individual actions, without the support of a detailed analysis on the real potentialities of the new products, can entail serious problems caused by inappropriate use of methods and/or inputs, making a wide discussion on the theme urgent, with establishment of a set of rules that supports such discussions.

Considering the images from Remote Sensing as growingly important inputs for cartography, it is emphasized that the diversity of new remote sensors, at different acquisition levels, and values of resolution and accuracy, allows to meet a variety of reference and thematic maps, in several scales.
