Papers by Olalekan Adekunle Isioye
South African Journal of Geomatics, 2015
The problem of flooding is becoming a global menace which must be tackled seriously as it usually... more The problem of flooding is becoming a global menace which must be tackled seriously as it usually leads to wanton destruction of lives and properties. Basawa Community and its environs are not left out of areas affected by this global phenomenon. This area is usually flooded annually during the raining season due to the poor drainage system existing in the locality. The stagnancy of water during the raining season causes water to flood into homes. This study focuses attention on Digital Terrain Analysis (DTA) of the study area. The effect of this DTA on the surface runoff were analyzed, this was achieved by generating and extracting contour data and planimetric features from a topographic survey and a high resolution satellite image of the area respectively, these information were then used to derive the Digital Elevation Model (DEM) of the area consequently used for surface runoff analysis of the area under investigation. The DEM of the study area was generated in a GIS environment...
Positioning, 2014
Single frequency GNSS receivers are the most widely used tools for tracking, navigation and geo-r... more Single frequency GNSS receivers are the most widely used tools for tracking, navigation and geo-referencing around the world. It is estimated that over 75% of all GNSS receivers used globally are single frequency receivers and users experience positioning error due to the ionosphere. To enable GNSS Single Frequency Precise Point Positioning (SFPPP), accurate a-prior information about the ionosphere is needed. The variation of the ionosphere is larger around the magnetic equator and therefore depends on latitude. It will be expected that SFPPP works better on latitude further from the magnetic equator. This present study aims to investigate the accuracy of some ionospheric error mitigation approaches used in single frequency precise point positioning (SFPPP) at several GNSS station in the new Nigerian GNSS Network (NIGNet) and two IGS sites in the low equatorial African region. This study covers two epochs of observation. The first consists of observation from three consecutive days (GPS week 1638; days 0, 1 and 2) that belongs to a period of low solar activities. The second epoch consists of observation from three consecutive days (GPS week 1647; days 2, 3 and 4) that belongs to a high solar activity and intense geomagnetic conditions. The estimated position for the GNSS stations from dual frequency measurement and their known ITRF solutions were used as a benchmark to assess the accuracy of SFPPP under four conditions i.e., SFPPP without ionospheric correction, SFPPP using final GIM models from the Centre for Orbit Determination in Europe( CODE), SFPPP with Klobuchar model, and SFPPP with a computed (local) model at each station. All computation was done using Leica Geo-office software. The result of the study clearly demonstrates the significance of removing or correcting for the effect of the ionosphere, which can result in up to 7 m displacement. It was recommended that GIMs from different organization should be investigated and also efforts should be towards improvement in algorithms and clock error modeling.
Advances in Meteorology, Jan 24, 2015
When compared to the wide range of atmospheric sensing techniques, global navigation satellite sy... more When compared to the wide range of atmospheric sensing techniques, global navigation satellite system (GNSS) offers the advantage of operating under all weather conditions, is continuous, with high temporal and spatial resolution and high accuracy, and has long-term stability. The utilisation of GNSS ground networks of continuous stations for operational weather and climate services is already in place in many nations in Europe, Asia, and America under different initiatives and organisations. In Africa, the situation appears to be different. The focus of this paper is to assess the conditions of the existing and anticipated GNSS reference network in the African region for meteorological applications. The technical issues related to the implementation of near-real-time (NRT) GNSS meteorology are also discussed, including the data and network requirements for meteorological and climate applications. We conclude from this study that the African GNSS network is sparse in the north and central regions of the continent, with a dense network in the south and fairly dense network in the west and east regions of the continent. Most stations lack collocated meteorological sensors and other geodetic observing systems as called for by the GCOS Reference Upper Air Network (GRUAN) GNSS Precipitable Water Task Team and the World Meteorological Organization (WMO). Preliminary results of calculated zenith tropospheric delay (ZTD) from the African GNSS indicate spatial variability and diurnal dependence of ZTD. To improve the density and geometry of the existing network, countries are urged to contribute more stations to the African Geodetic Reference Frame (AFREF) program and a collaborative scheme between different organisations maintaining different GNSS stations on the continent is recommended. The benefit of using spaced based GNSS radio occultation (RO) data for atmospheric sounding is highlighted and filling of geographical gaps from the station-based observation network with GNSS RO is also proposed.
Single frequency GNSS receivers are the most widely used tools for tracking, navigation and geo-r... more Single frequency GNSS receivers are the most widely used tools for tracking, navigation and geo-referencing around the world. It is estimated that over 75% of all GNSS receivers used globally are single frequency receivers and users experience positioning error due to the ionosphere. To enable GNSS Single Frequency Precise Point Positioning (SFPPP), accurate a-prior information about the ionosphere is needed. The variation of the ionosphere is larger around the magnetic equator and therefore depends on latitude. It will be expected that SFPPP works better on latitude further from the magnetic equator. This present study aims to investigate the accuracy of some ionospheric error mitigation approaches used in single frequency precise point positioning (SFPPP) at several GNSS station in the new Nigerian GNSS Network (NIGNet) and two IGS sites in the low equatorial African region. This study covers two epochs of observation. The first consists of observation from three consecutive days (GPS week 1638; days 0, 1 and 2) that belongs to a period of low solar activities. The second epoch consists of observation from three consecutive days (GPS week 1647; days 2, 3 and 4) that belongs to a high solar activity and intense geomagnetic conditions. The estimated position for the GNSS stations from dual frequency measurement and their known ITRF solutions were used as a benchmark to assess the accuracy of SFPPP under four conditions i.e., SFPPP without ionospheric correction, SFPPP using final GIM models from the Centre for Orbit Determination in Europe( CODE), SFPPP with Klobuchar model, and SFPPP with a computed (local) model at each station. All computation was done using Leica Geo-office software. The result of the study clearly demonstrates the significance of removing or correcting for the effect of the ionosphere, which can result in up to 7 m displacement. It was recommended that GIMs from different organization should be investigated and also efforts should be towards improvement in algorithms and clock error modeling.
Digital elevation model (DEM) represents a very important geospatial data type in the analysis an... more Digital elevation model (DEM) represents a very important geospatial data type in the analysis and modelling of different hydrological and ecological phenomenon which are required in preserving our immediate environment. DEMs are typically used to represent terrain relief and are particularly relevant for many applications such as soil erosion volume calculations, flood estimate, quantification of earth materials to be moved for channels, roads, dams, embankment etc. This study investigates the quality (in terms of elevation accuracy and relative altitudinal differences) of two publicly available elevation model datasets over parts of Northern Nigeria: i) the 3 arc second Shuttle Radar Topography Mission (SRTM) ver4.1 from CGIAR-CSI; and (ii) the 1 arc second Advanced Space borne Thermal Emission and Reflection Radiometer Global − DEM (ASTER-GDEM) ver1 from NASA/METI. The main features of these datasets are reported from a geodetic point of view. This study represents a follow up to Isioye et al., 2012, because
Digital Elevation Model (DEM) represents a very important geospatial data type in the analysis an... more Digital Elevation Model (DEM) represents a very important geospatial data type in the analysis and modelling of different hydrological and ecological phenomenon which are required in preserving our immediate environment. DEMs are typically used to represent terrain relief. DEMs are particularly relevant for many applications such as lake and water volumes estimation, soil erosion volumes calculations, flood estimate, quantification of earth materials to be moved for channels, roads, dams, embankment etc.
Precision Agriculture has evolved from a concept some decades ago into an emerging technology tod... more Precision Agriculture has evolved from a concept some decades ago into an emerging technology today. The catalyst for the emergence of Precision agriculture has been satellite positioning and navigation. The combination of Global Positioning System (GPS) and mobile mapping provide the agriculturist with a new capability of gathering information for implementing decision-based Precision Agriculture. While adoption of precision farming in wide concept has been modest in Nigeria the potential for using precision agriculture to address environmental, food security and sustainability problems seems not to be attracting political attention in Nigeria conditions. This paper discusses the applicability, opportunities of precision agriculture in Nigeria. It was identified that the small size of farms and fields in most of Nigerian agriculture limits economic gains from currently available precision farming technology. However, the public concerns for the environment and food security may mean that those potential benefits of precision agriculture are beginning to receive attention. Finally it was concluded that it is not impossible to adopt Precision agriculture in Nigeria but research efforts are needed to work out modalities for its adoption in the Nigerian agricultural scenario.
The water needs for Zaria and its environments for human and agricultural consumption is on the r... more The water needs for Zaria and its environments for human and agricultural consumption is on the rise due to increase in population and human activities. Identification of potential sites for Rain Water Harvesting (RWH) is an important step towards maximizing water availability for farming and other uses in Zaria. However, selection of appropriate sites from different RWH technologies on a large scale presents a great challenge, since the necessary biophysical data and infrastructure are often lacking. In Spite of several thousand years of experience in rainwater harvesting around the world, a significant question remains, on how to identify areas suitable for certain techniques of rainwater harvesting using improved techniques in Geomatics. Thus this project presents a Multi-Criteria Evaluation (MCE) approach, supported in Geographic Information System (GIS) to identify potential sites for RWH in the study area. A Multi-criteria Decision Support System (MDSS) was developed with the aim of providing a more flexible and accurate decisions to the decision makers for identify potential sites for RWH. The criteria factors taken into consideration for the MDSS include; rainfall data, slope map, soil information, drainage map, and land use/cover map from the 'systeme pour l'observation de la terre'(SPOT 5) and LANDSAT satellite imagery respectively. The image processing software 'Integrated Land and Water Information System (ILWIS)' and GIS software ArcGIS 9.3 were used to process the images and to establish a geo-information system comprising digital data sets. The Boolean ranking method was used to calculate the weight for each factor and in the MCE the weighted linear combination (WLC) involving weighted overlay was used in the MDSS operation. The MDSS supported conditions for identifying potential in-situ, ponds, rock catchments and dam sites. The outputs are maps showing potential sites suitable for each rainwater harvesting technique and water storage systems in Zaria.
Information Manager (The), 2008
ABSTRACT This paper examines the stability of some benchmarks on the main campus of Ahmadu Bello ... more ABSTRACT This paper examines the stability of some benchmarks on the main campus of Ahmadu Bello University, Zaria, and reports the deformation studies of the area around the University dam. This dam serves as the main storage reservoir for the water supply to the University and surrounding communities. In order to study the deformation around the University dam and the stability of benchmarks, several surveys were carried out between 1976 and 2006. Within the period under review, it was revealed that the maximum downward displacement (settlement) of 96.44mm was recorded between 1976 and 2006 for a monitoring station (CP4) situated centrally along the embankment of the dam. The maximum upward displacement (uplift) of 8.03mm was recorded between 1976 and 2002 at a ground point (CP12) located in a roundabout in front of Faculty of Medicine of the University. The monitoring Station CP4 had the greatest average absolute displacement of 3.22mm per annum over the period of thirty years. Detailed results and analysis will be discussed in this paper.. The Information Manager Vol. 7 (2) 2007: pp. 28-39
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Papers by Olalekan Adekunle Isioye