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CORS usage for GPS survey in the greater accra region: Advantages, limitation, and suggested remedies / Sebastian Botsyo in Journal of Geovisualization and Spatial Analysis, vol 4 n° 2 (December 2020)  

Public [article]  inJournal of Geovisualization and Spatial Analysis > vol 4 n° 2 (December 2020) . - n° 20 Titre : CORS usage for GPS survey in the greater accra region: Advantages, limitation, and suggested remedies Type de document : Article/Communication Auteurs : Sebastian Botsyo, Auteur ; Bernard Borketey Bortei, Auteur ; John Ayer, Auteur Année de publication : 2020 Article en page(s) : n° 20 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] balise [Termes IGN] Continuously Operating Reference Station network [Termes IGN] géopositionnement [Termes IGN] Ghana [Termes IGN] International Terrestrial Reference Frame [Termes IGN] positionnement statique [Termes IGN] station de référence [Termes IGN] station permanente [Termes IGN] système de référence local Résumé : (auteur) The use of Continuously Operating Reference Stations (CORS) enables surveyors to differentially correct static Global Positioning System (GPS) measurements. CORS are designed to support the broad spectrum of post-processed, relative GPS techniques, and applications. Enhancing geospatial positioning applications of CORS data involves the critical role in defining the nation’s geodetic reference system. With the establishment of a coordinated system of CORS, an Online Positioning User Service can become available for processing in single positioning mode to provide corresponding accurate and homogeneous positional coordinates. The Survey and Mapping Division (SMD), Lands Commission of Ghana, has established four CORS in the Greater Accra, and Ashanti, Western and Brong-Ahafo Regions, respectively, to provide a basic CORS network in accordance with the International Terrestrial Reference Frame (ITRF). However, most surveyors continue to reference their works in these regions to ground survey beacons that have been coordinated and adjusted by variable survey methods. This obviously makes homogeneity of data unpredictable. This study explored the extent of usage of existing CORS network established by SMD with particular focus on the CORS in the Greater Accra Region for GPS surveys and to determine its usefulness in ensuring homogeneity in GPS data collection. The professional participatory (interviews) technique was coupled with differential GPS field observations with the CORS as reference in one case and ground control stations as reference in the other in making relatively conclusive analysis. Test results showed that GPS field survey of an approximate range of 23 km away from the Accra CORS yielded an average positional change in Northings and Eastings of − 0.790 m, − 0.176 m and − 0.681 m, − 0.098 m for single and dual frequency, respectively, in different localities within the study area. Beyond a range of 25 km from the Accra CORS, the average positional change in Northings and Eastings are − 0.536 m, − 0.007 m and − 1.370 m, 0.334 m for single and dual frequency respectively. Of 128 geomatic professionals interviewed, 39% are aware of the availability of COR stations in Greater Accra, 61% are unaware, and 28% are aware and users of the Accra CORS whereas 11% are aware but non-users of the Accra COR station. Of all users sampled, 17.5% are regular and frequent users of the Accra COR station and 10.5% are occasional or seldom users. The results show that the Accra CORS is vital to ensuring a uniform homogenous GPS data. However, very few people are using it due to low public awareness of the usefulness of the CORS among professional surveyors and other users and a cumbersome, bureaucratic nature in CORS data acquisition for post-processing and RTK GPS surveys. Numéro de notice : A2020-723 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s41651-020-00061-8 date de publication en ligne : 11/09/2020 En ligne : https://doi.org/10.1007/s41651-020-00061-8 Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96324 [article]

Least squares support vector machine model for coordinate transformation / Yao Yevenyo Ziggah in Geodesy and cartography, vol 45 n° 1 (2019)  

Public [article]  inGeodesy and cartography > vol 45 n° 1 (2019) . - pp 16 - 27 Titre : Least squares support vector machine model for coordinate transformation Type de document : Article/Communication Auteurs : Yao Yevenyo Ziggah, Auteur Année de publication : 2019 Article en page(s) : pp 16 - 27 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] Ghana [Termes IGN] méthode des moindres carrés [Termes IGN] projection conforme [Termes IGN] résidu [Termes IGN] séparateur à vaste marge [Termes IGN] transformation affine [Termes IGN] transformation de coordonnées Résumé : (auteur) In coordinate transformation, the main purpose is to provide a mathematical relationship between coordinates related to different geodetic reference frames. This gives the geospatial professionals the opportunity to link different datums together. Review of previous studies indicates that empirical and soft computing models have been proposed in recent times for coordinate transformation. The main aim of this study is to present the applicability and performance of Least Squares Support Vector Machine (LS-SVM) which is an extension of the Support Vector Machine (SVM) for coordinate transformation. For comparison purpose, the SVM and the widely used Backpropagation Neural Network (BPNN), Radial Basis Function Neural Network (RBFNN), 2D conformal and affine methods were also employed. To assess how well the transformation results fit the observed data, the root mean square of the residual horizontal distances and standard deviation were used. From the results obtained, the LS-SVM and RBFNN had comparable results and were better than the other methods. The overall statistical findings produced by LS-SVM met the accuracy requirement for cadastral surveying applications in Ghana. To this end, the proposed LS-SVM is known to possess promising predictive capabilities and could efficiently be used as a supplementary technique for coordinate transformation. Numéro de notice : A2019-482 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.3846/gac.2019.6053 date de publication en ligne : 17/04/2019 En ligne : https://doi.org/10.3846/gac.2019.6053 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=93629 [article]

Performance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions / O. E. Abe in Journal of geodesy, vol 91 n° 4 (April 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 4 (April 2017) . - pp 409 - 417 Titre : Performance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions Type de document : Article/Communication Auteurs : O. E. Abe, Auteur ; X. Otero Villamide, Auteur ; C. Paparini, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 409 - 417 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] champ géomagnétique [Termes IGN] erreur systématique [Termes IGN] Espagne [Termes IGN] estimation statistique [Termes IGN] étalonnage [Termes IGN] évaluation [Termes IGN] Ghana [Termes IGN] latitude [Termes IGN] performance [Termes IGN] signal GNSS [Termes IGN] teneur totale en électrons [Termes IGN] traitement du signal Résumé : (auteur) Global Navigation Satellite Systems (GNSS) have become a powerful tool use in surveying and mapping, air and maritime navigation, ionospheric/space weather research and other applications. However, in some cases, its maximum efficiency could not be attained due to some uncorrelated errors associated with the system measurements, which is caused mainly by the dispersive nature of the ionosphere. Ionosphere has been represented using the total number of electrons along the signal path at a particular height known as Total Electron Content (TEC). However, there are many methods to estimate TEC but the outputs are not uniform, which could be due to the peculiarity in characterizing the biases inside the observables (measurements), and sometimes could be associated to the influence of mapping function. The errors in TEC estimation could lead to wrong conclusion and this could be more critical in case of safety-of-life application. This work investigated the performance of Ciraolo’s and Gopi’s GNSS-TEC calibration techniques, during 5 geomagnetic quiet and disturbed conditions in the month of October 2013, at the grid points located in low and middle latitudes. The data used are obtained from the GNSS ground-based receivers located at Borriana in Spain (40∘N, 0∘E; mid latitude) and Accra in Ghana (5.50∘N, −0.20∘E; low latitude). The results of the calibrated TEC are compared with the TEC obtained from European Geostationary Navigation Overlay System Processing Set (EGNOS PS) TEC algorithm, which is considered as a reference data. The TEC derived from Global Ionospheric Maps (GIM) through International GNSS service (IGS) was also examined at the same grid points. The results obtained in this work showed that Ciraolo’s calibration technique (a calibration technique based on carrier-phase measurements only) estimates TEC better at middle latitude in comparison to Gopi’s technique (a calibration technique based on code and carrier-phase measurements). At the same time, Gopi’s calibration was also found more reliable in low latitude than Ciraolo’s technique. In addition, the TEC derived from IGS GIM seems to be much reliable in middle-latitude than in low-latitude region. Numéro de notice : A2017-107 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern En ligne : http://dx.doi.org/10.1007/s00190-016-0972-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84497 [article]

Analysis of desertification in the Upper East Region (UER) of Ghana using remote sensing, field study, and local knowledge / Alex B. Owusu in Cartographica, vol 48 n° 1 (March 2013)  

Public [article]  inCartographica > vol 48 n° 1 (March 2013) . - pp 22 - 37 Titre : Analysis of desertification in the Upper East Region (UER) of Ghana using remote sensing, field study, and local knowledge Type de document : Article/Communication Auteurs : Alex B. Owusu, Auteur ; Guido Cervone, Auteur ; Sheryl Luzzadder-Beach, Auteur Année de publication : 2013 Article en page(s) : pp 22 - 37 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection [Termes IGN] désertification [Termes IGN] flore locale [Termes IGN] Ghana [Termes IGN] image Landsat-TM [Termes IGN] image NOAA-AVHRR [Termes IGN] Normalized Difference Vegetation Index [Termes IGN] production agricole [Termes IGN] revêtement [Termes IGN] zone semi-aride Résumé : (Auteur) Les techniques de télédétection basées sur des données satellites multispectrales offrent un potentiel exceptionnel pour détecter, quantifier, surveiller et cartographier la dégradation des sols. Toutefois, les données de télédétection ne fournissent pas, en elles-mêmes, d'information sur la manière dont la dégradation des sols affecte certains aspects socio-politiques et économiques de la population vivant dans ces régions. Le système Continuous Cycle of Land Degradation (CCoLD) que nous avons créé sert à quantifier le degré de gravité de la dégradation des sols dans la Région du Haut Ghana oriental. Nous l'avons associé à un indice de végétation par différence normalisée (IVDN) basé sur la télédétection déterminée à l'aide du Global Inventory Modeling and Mapping Studies (GIMMS) IVDN, de données prises sur le terrain et de données sur la production alimentaire. De plus, on a mené une étude sur le terrain dans la Région du Haut Ghana oriental, une région transitionnelle semi-aride qui joue un rôle important dans la production alimentaire du Ghana, et on a comparé ces résultats aux images de télédétections multitemporelles. En plus des mesures générales, l'étude sur le terrain comprenait un questionnaire permettant aux résidents de la région d'évaluer l'impact de la dégradation des sols sur leur qualité de vie. Les données télédétectées démontrent une dégradation localisée à grande envergure. L'étude sur le terrain, ainsi que des données au sujet des cultures agricoles, suggèrent également une dégradation généralisée des sols. Cependant, nos observations sur le terrain suggèrent de la succession écologique là où des prêles localement adaptées ont été déplacées par des herbes denses et écologiquement efficaces, à vie courte et à maturation rapide. La convergence des évidences donne à penser que la dégradation des terres s'est bien avancée et que des efforts communautaires plus concentrés seraient nécessaires pour combattre la dégradation ainsi que pour restaurer l'intégrité de l'écosystème. Numéro de notice : A2013-140 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article En ligne : http://www.utpjournals.press/doi/full/10.3138/carto.48.1.1065 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32278 [article]

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Customary tenure and good governance / A. Arko-Adjei in GIM international, vol 25 n° 3 (March 2011)  

Public [article]  inGIM international > vol 25 n° 3 (March 2011) . - pp 27 - 31 Titre : Customary tenure and good governance Type de document : Article/Communication Auteurs : A. Arko-Adjei, Auteur Année de publication : 2011 Article en page(s) : pp 27 - 31 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Cadastre étranger [Termes IGN] accès aux données localisées [Termes IGN] aménagement du territoire [Termes IGN] coutume [Termes IGN] droit coutumier [Termes IGN] gestion foncière [Termes IGN] Ghana [Termes IGN] institution administrative Résumé : (Auteur) Although customary tenure institutions come under considerable strain and their functions tend to be weakened by existence of a statutory institutional framework, many people in peri-urban areas continue to rely on such arrangements for land delivery. These institutions maintain their traditional power and social responsability for allocating the right to use land, resolve conflicts, and carry out overall management of customary land. Yet little attention has been paid to whether or not the activities of these indigenous institutions meet good governance objectives in land administration. The issue has been studied in Ghana. Numéro de notice : A2011-066 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article En ligne : http://www.gim-international.com/content/article/customary-tenure-and-good-gover [...] Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30847 [article]

Detection, measurement and prediction of shoreline recession in Accra, Ghana / K. Appeaning Addo in ISPRS Journal of photogrammetry and remote sensing, vol 63 n° 5 (September - October 2008)

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The application of GIS in the lands sector of a developing country: challenges facing land administrators in Ghana / I. Karikari in International journal of geographical information science IJGIS, vol 19 n° 3 (march 2005)

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Systems of land registration / Jaap Zevenbergen (2002)

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The utilization of SPOT satellite XS imageries for the characterization of inland valleys of the northen region of Ghana - initial evaluation / E. Amamoo-Otchere (1991)

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Lexique français - kabiye - ewe / Bassari Ebia (1974)

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L'Afrique occidentale / Assane Seck (1967)

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Les Sarakollé du Guidimakha / J.H. Saint-Pere (1925)

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Le Gana et le Mali et l'emplacement de leur capitales / Maurice Delafosse (1924)

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