African Association of
Remote Sensing of the Environment
 
 

Articles

  • 09 Jul 2015 9:48 AM | AARSE Admin (Administrator)

    It is necessary that African scientists look at strengthening their capacities in new Earth Observation applications. One of the evolved technologies is polarimteric radar data and its efficiency in studying earth surface processes including environment related issues. However, questions are: What is the main constraint? Is data availability the key issue to develop technical capacity? NARSS has started to explore the potentiality of this field through international cooperation and partnership and found that to be an avenue for such capacities. An agreement between NARSS and the Canadian Space Agency (RADARSAT-2 SOAR-AF LOAN AGREEMENT LI-24887) enabled to provide the Polarimetric SAR data and to develop and strengthen our capacities in RadarSat-2 data processing and analysis.


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  • 15 Jan 2015 1:28 PM | AARSE Admin (Administrator)
    The GIS model enabled to draw a scenario to project the urban growth of Addis Ababa in 2025. The digital and intelligent data model could help decision makers in selecting the appropriate locations for further development of urban to meeting the population increase. 


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  • 09 Oct 2014 1:56 PM | AARSE Admin (Administrator)

    Abstract

    We describe a method for improving Earth observation satellite image resolution, for specific areas of interest where the sensor design resolution is insufficient. Our method may be used for satellites with yaw-steering capability, such as NigeriaSat-2. We show that, according to the slanted edge modulation transfer function (MTF) plots, the effective resolution obtained by simulated yaw-steering of a satellite yielded a 138% improvement in resolution. This result equates to obtaining a 2.1m resolution image from a sensor designed to acquire 5m resolution images. 

  • 09 Oct 2014 1:54 PM | AARSE Admin (Administrator)

    Abstract

    The study mainly investigates the ability to provide a guideline on the exact areas available for rehabilitation and determine the most desirable species that are 
    suitable in order to achieve a desirable success rate. Specifically, this research intends to:
    • Provide a land use map which can further be used to estimate the target forest area to be rehabilitated.
    • Identify areas that can either be planted physically or be protected to allow for natural regeneration.
    • Provide a framework for species site matching.
    The area of study is East Mau forest located in Nakuru Country, Kenya and is part of the larger Mau eco system. 

  • 09 Oct 2014 1:48 PM | AARSE Admin (Administrator)

    Application field: Humanitarian relief support, mission planning, conflict prevention,
    crisis monitoring. From a humanitarian point of view, there is no doubt that the most
    critical parameter to be mapped and monitored is the number of people affected by a
    crisis or disaster. This applies to all phases of the disaster cycle, ranging from the
    alerting and emergency response phases to recovery and rehabilitation phases.
    Remote sensing may, however, at best provide only indications of human presence,
    since individuals are not directly visible. Areas such as IDP camps can show rapid
    changes in annual population averages, with sudden, dramatic increases or decreases
    in numbers. As a result of such rapid population changes in these ephemeral
    settlements in situ population censuses are often the only means of acquiring relevant
    population figures within the time frame required for humanitarian aid.
    Methodology used / workflow: A workflow for conditioned information comprising
    situation awareness, user specifications, data integration, automated data analysis,
    added value products and scientific visualization (maps and globe browsers).


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  • 18 Nov 2013 4:28 PM | Administrator (Administrator)

    Abstract

    Nigeria is blessed with a large expanse of forest cover but this important resource is not sustainably used, managed and/or conserved. Historically, forestry development in Nigeria began with reservation of forest lands in order to manage, maintain forest reserves and provide a supply of timber. This was followed by exploitation of forest resources to meet both export and burgeoning local demand as well as to earn much needed foreign exchange. With the country’s independence in 1960, development phase of the Nigerian forest resources management began which focus on the development of forest plantations. The records in the Federal Department of Forestry as of 2006 shows that Nigeria has a total of 1,160 constituted forest reserves including 6 National Parks, 20 Game and Wildlife sanctuaries, 13 proposed Game Reserves/Wildlife Sanctuaries and 8 Strict Nature Reserves. These areas which cover about 107,527 km2 are designated for conservation, management, and propagation of wild animals including the protection and management of critical habitats.

    For about 40years now, Nigeria's forests including the conservation areas have continued to shrink, especially in the north, where uncontrolled commercial exploitation of privately owned forests began in the late nineteenth century. Presently, the rate of deforestation is now estimated at about 3.5% per annum translating to a loss of 3,500–4,000 km2 of forest land per year while current level of demand for forest products outstrips the sustainable level of supply. This situation is expected to deteriorate further in future if adequate conservation measures are not properly introduced. For reliable conservation strategies for forestry sustainability in Nigeria, this study therefore, recommended the following: a review of forest policies, afforestation and reforestation methods, improved enforcement, agroforestry practice and adequate funding, restoration of degraded land, control of bush burning and forest fires, and more importantly adoption of local/traditional knowledge in planning and execution of forestry projects as well as forest monitoring using remotely sensed data.

    Keywords: Forests, management phases, challenges, remote sensing


    Ayeni A. O. (Ph.D.)

    Department of Geography, University of Lagos, Lagos - Nigeria


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  • 12 Oct 2012 4:00 PM | Administrator (Administrator)

    Abstract

    Nigerian coastline is a product of several geomorphologic, biogenic and anthropogenic processes taking place, causing erosion of the shoreline especially at coastline bend including Ondo and Delta States while deposition is taking place at the delta region of the coastline. The Ondo - Delta coastline is a 150 kilometer stretch of different structures and characteristics raging from coarse beach, mud beach and fine sand.

    The study utilize multi-date satellite remote sensing data of three epochs spanning twenty five (25) years complemented with field work, in order to identify the forces at play and the dynamics of the Nigerian coastlines including geomorphologic processes taking place. It also uses the process of digital shoreline system analysis toolkit to calculate the process of coastline movement by using transects perpendicular to a baseline.

    It was observed that the coastline has undergone a phase of erosion and deposition, between 1986 and 2000 erosion was the most dominant process resulting in a 22% loss of coastline area. However between 2000 and 2011 the coastline advanced by 39%, this corresponds to an overall increase in the coastline of 66km in the same period.

    The paper concludes that the dominant processes in the Ondo – Delta coastline are mainly erosion and deposition; consequently communities around Ondo such as Awoye, Molume, and Oruna are most vulnerable to erosion. On the other hand around the Delta axis communities such as Yokri Egbe, Jalla and Kantu experience more deposition process.


    * Fabiyi. O.O. : Regional Centre for Training in Aerospace Surveys. Ile Ife Nigeria

    Ikhuoria I.A.: Regional Centre for Training in Aerospace Surveys. Ile Ife Nigeria

    Yesuf G. : Regional Centre for Training in Aerospace Surveys. Ile Ife Nigeria

    *Corresponding Author


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    This post was written by Prof. Oluseyi Fabiyi (Regional Centre for Training in Aerospace Surveys, Ile-Ife Nigeria). Contact him at fabiyi@rectas.org for more information.

  • 12 Oct 2012 4:00 PM | Administrator (Administrator)

    Nigeria has about 68, 207 Square kilometers of wetlands out of the 923,000 Square kilometers land areas. A significant part of Nigerian wetlands  are within urban areas holding high potentials for dry season farming and supplying all year round farm produce for urban teaming population.

    Wetlands are very valuable areas for rural communities and peri-urban agriculture and they serve as the dominant agricultural lands in the arid parts of Nigeria. The South western part of Nigeria is served with natural drainage networks with their rich agricultural potentials from wetlands. These networks of river systems are available for agriculture for most part of the year especially around the perennial river systems. The wetlands are submerged for some period of the year and could be used for irrigation purpose.

    The study used SPOT 5 satellite remote sensing obtained from google earth and other auxiliary soruces to map the wetland resources within the lower Osun river catchment area and delimited areas accessible for urban and peri-urban agriculture for the river basin.

    The total wetlands and the farming potentials of the area were computed and estimated for the use of urban farming population. The wetland resources were categorized based on the accessibility to farming urban population.

     

    *Fabiyi. Oluseyi . O
    Regional Centre for Training in Aerospace Surveys. Ile Ife Nigeria
    E-mail: fabiyi@rectas.org, Tel: +234-8034085463
    Ige-Olumide  Olusola .O.
    Regional Centre for Training in Aerospace Surveys. Ile Ife Nigeria
    Fabiyi, Olukemi. A
    Agricultural Research Council of Nigeria. Abuja Nigeria

    *Lead Author


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    This post was written by Prof. Oluseyi Fabiyi (Regional Centre for Training in Aerospace Surveys, Ile-Ife Nigeria). Contact him at fabiyi@rectas.orgfor more information.

  • 12 Oct 2012 10:00 AM | Administrator (Administrator)

    Lien entre enneigement et climat à grande échelle sur le Haut Atlas Marocain à l’aide
    des images MODIS (Période 2000-2010) 
    A.MARCHANE, L JARLAN, L.HANICH, et A.BOUDHAR

    Faculté des Sciences et Techniques Guéliz, Département des Sciences de la Terre, laboratoire de Géoressources-Unité associée au CNRST (URAC42), BP 549, 40 000 Marrakech, Maroc. 
    E-mail : marchane.gat@gmail.com
    Centre d’Etudes Spatiales de la Biosphère, 18, Av. E. Belin 31401 Toulouse, France 
    Faculté des Sciences et Techniques, BP 523, Béni-Mellal, Maroc

    Résumé :
    Dans les pays du sud de la Méditerranée et du Moyen Orient, l’eau est une ressource rare: 180 millions d’habitants disposent de moins de 1000 m d’eau par an et par habitant et 80 millions sont en situation de pénurie (moins de 500m/habitant /an) alors que la demande a doublé depuis 50 ans. Pour de nombreux bassins versants en méditerranée semi aride, la zone de production de l’eau est située en montagne et la présence de neige constitue un réservoir non négligeable. Malgré l’importance de la neige dans le bilan hydrique régional et comme indicateur de changement climatique, peu d’études se sont focalisées jusqu’à présent sur l’étude du lien entre l’enneigement et le climat à grande échelle.

    De longues séries temporelles de données satellitaires existent désormais. Dans les régions semi-arides qui ne disposent pas d’un panel opérationnel de suivi au sol (réseaux de mesures météorologiques …), ces séries d’observation représentent un témoin unique de l’évolution des ressources qui n’a été que peu exploité jusqu’à présent en Méditerranée. Dans ce contexte, nous avons caractérisé la variabilité spatio-temporelle du couvert neigeux sur le Haut Atlas à partir des produits journaliers de couverture neigeuse acquises par l’instrument MODIS (figure 1). Plusieurs traitements basés sur des filtrages spatio-temporel (J. Tong et al. 2009 ; J. Parajka et al, 2010) visant à éliminer les pixels nuageux en particulier sont appliqués et évalués. Enfin, certaines caractéristiques saisonnières (durée d’enneigement, date des premières neiges et surface enneigé maximum) sont extraites.

    Figure 1: Cycles annuels d’enneigement (moyenne de 15 jours) sur le Haut Atlas du Tensift pour la période 2000-2010 (produits MODIS MOD10A2) 

    Dans un 2ème temps, nous avons étudié le lien entre, d’une part, la dynamique atmosphérique et océanique à grande échelle vue à travers l’oscillation Nord Atlantique (NAO) et les températures de surface de l’océan atlantique (SST) et, d’autre part, la variabilité du couvert nival sur cette région.

    Les résultats montrent que la variabilité interannuelle est extrêmement forte en terme de cycle annuel d’enneigement, de surface enneigée maximum et de date des premières neiges. L’étude du lien entre la dynamique atmosphérique et océanique à grande échelle (NAO et SST) et la variabilité du couvert enneigé sur cette région, montrent notamment qu’une NAO en phase négative durant le mois de février est légèrement favorable à l’enneigement sur le Haut Atlas. La faiblesse de cette relation,
    même si son signe négatif est cohérent avec les études précédentes montrant le lien NAOprécipitations sur l’Afrique du Nord est étonnant. L’analyse de la relation entre la NAO et la température mesurée à la station d’Oukaimeden à 3200m d’altitude a permis de montrer que la phase négative de la NAO conduisait dans un même temps à un réchauffement, donc plutôt défavorable à l’enneigement. Ce double impact opposé de la NAO sur la température et les précipitations, deux facteurs régissant le déclenchement d’un évènement neigeux, pourrait expliquer la faible relation obtenu entre NAO et enneigement. Enfin, nous avons montré une relation forte entre les anomalies de température de surface des océans dans les régions tropicales et équatoriales à la fin de l’été et l’enneigement sur le Haut Atlas. Ces résultats corroborent notamment de précédentes études et font des SST dans cette région de l’Atlantique un candidat potentiel intéressant pour la prévision précoce du couvert neigeux sur le Haut Atlas.

    De manière générale, cette étude montre l’intérêt de l’utilisation des données de la 
    télédétection pour caractériser l’enneigement en montagne semi aride et permet de déterminer les facteurs synoptiques qui régissent la dynamique de cet enneigement 

    Mots clés : hydrologie, télédétection, climat, semi-aride, neige, Haut Atlas

    Références : 
    - J. Tong, S.J.Déry, et P.L.Jackson, 2009, Interrelationships between MODIS/Terra remotely
    sensed snow cover and the hydrometeorology of the Quesnel River Basin, British Columbia,
    Canada, (Hydrol. Earth Syst. Sci., 13, 1439–1452, 2009) 
    - J.Parajka, M. Pepe, A. Rampini,S. Rossi,G. Bloschol, 2010, A regional snow-line method for
    estimating snow cover from MODIS during cloud cover,(Journal of hydrology, 381,203212,2010)

    Cet article a été écrit par Ahmed Marchane (università © Cadi Ayyad). Contactez-le à marchane.gat@gmail.com pour plus d'informations.

  • 11 Oct 2012 11:00 AM | Administrator (Administrator)

    Abstract

    The Gorongosa National Park, located in Central Mozambique, has been undergoing rehabilitation, after years of civil strife lasting from 1975 to 2004, which destroyed most of the national parks' physical and human infrastructure. Mount Gorongosa was proclaimed part of Gorongosa National Park by a government decree published in May 2010 and is the main source of water for the park. One of the biggest conservation challenges for the Gorongosa National Park, is that Mount Gorongosa, geographically detached from the core park, located in north west of the original 4,000 square kilometre park, and one of the few remaining rainforests of eastern Africa, is under threat from excessive deforestation, due mainly from increasing human settlement. The objective of the research was therefore to evaluate the land use change process on and around Gorongosa Mountain from 2000 to 2010, so as to determine the rate, state, magnitude and possible impacts of forestry loss on the Gorongosa Mountain. Land use change was analysed using Landsat satellite images of the years 2000, 2005, 2010. An IKONOS image of 2010 was used for ground truthing and this was complemented with available field survey data. Change detection was carried out on the images for the different year intervals. From the classified images, it was revealed that Montane forest declined by 13% from 29% in 2005 to 16% of the total mountain area in 2010 and this was largely attributed to cutting down of trees for cultivation purposes. Wooded grasslands, however increased from 3% to 22% and this was attributable to the practice of slash and burn agriculture around the mountain as most of the wooded grassland areas were areas of vegetation regeneration after the areas had been abandoned. For the years 2000 and 2005 an analysis of net vegetation changes particularly focusing on the Montane forest revealed that more area was lost to wooded areas and cleared areas in the magnitude of 1.5% and 3.8% respectively. Losses to cultivated areas contributed marginally in the region of 0.3%. However, between 2005 and 2010, cultivated areas, wooded grassland, and cleared areas contributed 5.5%, 4% and 1 % respectively to the loss in Montane forest on the mountain. The most dominant farming activity threatening the mountain is the cultivation of potatoes on the rich fertile mountain slopes. Overall, the continuous loss of protective vegetative cover from the mountain will not only results in loss of flora and fauna, but will also result in drying of springs, soil erosion, flush floods, loss of animal habitats, reduced water flow and siltation of Lake Urema. This will eventually leads to loss of livelihoods as people will not be able to access the traditional non timber forest products from the mountain. There is therefore an urgent need to preserve the remaining forest areas on the mountain so as to protect the water sources of Lake Urema, hence protect the “pulse” of Gorongosa National Park. There is also need to intensify reforestation activities especially on the highly sensitive areas like river sources especially to combat erosion. Since there are people already residing within the park, there is need to intensify conservation education measures so as to protect the biodiversity on the mountain and on the plains.


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    This post was written by Sam Kusangaya (Gorongosa National Park). Contact him at kusangayas@yahoo.com for more information.

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