• Optical Remote Sensing of Land Surfaces
• Microwave Remote Sensing of Land Surfaces
• Land Surface Remote Sensing in Agriculture and Forest
• Land Surface Remote Sensing in Continental Hydrology
• Land Surface Remote Sensing in Urban and Coastal Areas
• Land Surface Remote Sensing: Environment and Risks

Cette série s’adresse à celles et ceux qui souhaitent découvrir ou approfondir la télédétection appliquée aux surfaces continentales. Chaque ouvrage de cette série contient une douzaine de chapitres.

Cette série est le fruit d’une riche collaboration entre des scientifiques de renommée internationale dans leurs domaines respectifs, incluant des co-auteurs canadiens. Les éditeurs sont les chercheurs Nicolas Baghdadi (PhD) and Mehrez Zribi (PhD) bien connus au Québec et en Europe.

Plus de détails ainsi qu’un sous-ensemble de l’ouvrage en pdf sur le site :

(1) http://www.iste.co.uk/index.php?p=a&ACTION=View&id=1057

ou

(2) http://store.elsevier.com/searchResults.jsp?_sbterm=&_requestid=4227446 (en tapant ensuite baghdadi ou zribi)

La parution de l’édition française (version originale) des volumes est prévue pour le mois de novembre prochain.

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Towards a Conceptual Framework for WikiGIS

Wided Batita, Stéphane Roche, Yvan Bédard and Claude Caron

Résumé
As an emerging complex concept, GeoDesign requires an innovative theoretical basis, tools, supports and practices. For this reason, we propose a new concept, “WikiGIS”, designed to answer some dimensions of the GeoDesign process. WikiGIS focuses on the needs of GeoDesign, but we leave the door open for future improvement when tested in other areas that may have additional needs. WikiGIS is built on Web 2.0 technologies—and primarily on wiki—to manage the tracking of participants’ editing (i.e., managing the contributions history). It also offers GIS functions for geoprocessing and a design-based approach for sketching proposals. One of the main strengths of WikiGIS is its ability to manage the traceability of contributions with an easy and dynamical access, data quality and deltification. The core of this paper consists of presenting a conceptual framework for WikiGIS using UML diagrams. A user interface is presented later to show how our WikiGIS proposal works. This interface is simply a means to illustrate the concepts underlying WikiGIS.

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Abstract

Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF.

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