by Dodo J. D., Ekeanyanwu U. O. and Ono M. N.
Review Article
Throughout Nigeria, the structure and facilities needed for the operation of a Global Navigation Satellite System (GNSS) based Continuously Operating Reference Stations (CORS) has been set up at different locations in the country generally known as NIGerian Reference GNSS NETwork (NIGNET) for surveying and mapping. Different researchers have conducted investigations into the effect of the troposphere over the NIGNET. This study aims at comparing analytically the effect of five different a priori tropospheric models on GNSS signals in Southern Nigeria with a view to obtaining the best-fit model. The objectives include evaluation of the global tropospheric models in the baseline and position domain; and determining the best model for southern Nigeria. Observational data used were obtained from Office of Surveyor General of Nigerian Mapping Agency (OSGoF). GPS data were obtained from October 2010, to April 2011. Six processing strategies were employed these include; application of no model, application of five global tropospheric delay models (Black, Davis et al, Hopfield, Neil and Saastamoinen) models using Trimble Total Control software version 2.73. Each of the strategies went through free and constrained adjustments and the results were compared. The five models investigated show no significance difference in their performance; better improvements in the position domain were achieved by the application of the Niell model compared to the rest of the models. The Niell model produced a better mitigation of the tropospheric delay, with an average percentage improvement of 67.1%; while Davis et al, the modified Hopfield and Saastaminen models have 70%, 71.1% and 71.7% percentage improvement respectively. The result also indicates that, the Neill model gave the best result and a better improvement in the entire network with the lowest mean average zenith tropospheric delay (ZTD) of 2.535m and least average RMSE of 0.67m. The specific objective of this study is to determine the best tropospheric delay for the study area and to recommend to practicing Surveyor on the model to be used. The research shows that, the Neil model gives the best result when compared with other model. Hence, it is recommended when processing GNSS observations for tropospheric delay to obtain a more accurate result.
Journal of Geosciences and Geomatics. 2019, 7(4), 201-211. DOI: 10.12691/jgg-7-4-5
Pub. Date: September 15, 2019
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by Clement E Bassey, Aniefiok E. Ite, Ekpedeme R. Asuaiko and Emmanuella E. Aidoko
Original Research
Textural characterization and heavy mineral studies of beach sediments in Ibeno and Eastern Obolo Local Government Areas of Akwa Ibom State were carried out in the present study. The main aim was to infer their provenance, transport history and environment of deposition. Sediment samples were collected at the water–sediment contact along the shoreline at an interval of about 3m. Ten samples were collected from study location 1 (Ibeno Beach) and twelve samples were collected from study location 2 (Eastern Obolo Beach). A total of twenty–two samples were collected from the field and brought to the laboratory for textural and compositional analyses. The results showed that the value of graphic mean size ranged from 1.70Ф to 2.83Ф, sorting values ranged from 0.39Ф – 0.60Ф, skewness values ranged from -0.02 to 0.10 while kurtosis values ranged from 1.02 to 2.46, indicating medium to fine grained and well sorted sediments. This suggested that the sediments have been transported far from their source. Longshore current and onshore–offshore movements of sediment are primarily responsible in sorting of the heavy minerals. The histogram charts for the different samples and standard deviation versus skewness indicated a beach environment of deposition. This implies that the sediments are dominated by one class of grain size; a phenomenon characteristic of beach environments. The heavy mineral assemblages identified in this research work were rutile, zircon, tourmaline, hornblende, apatite, diopside, glauconite, pumpellyite, cassiterite, epidote, garnet, augite, enstatite, andalusite and opaque minerals. The zircon-tourmaline-rutile (ZTR) index ranged from 47.30% to 87.00% with most of the samples showing a ZTR index greater than 50%. These indicated that the sediments were mineralogically sub-mature and have been transported far from their source. The heavy minerals identified are indicative of being products of reworked sediments of both metamorphic (high rank) and igneous (both mafic and sialic) origin probably derived from the basement rocks of the Oban Massif as well as reworked sediments of the Benue Trough. Therefore, findings from the present study indicated that erosion, accretion, and stability of beaches are controlled by strong hydrodynamic and hydraulic processes.
Journal of Geosciences and Geomatics. 2019, 7(4), 191-200. DOI: 10.12691/jgg-7-4-4
Pub. Date: August 29, 2019
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by Mikir Kassaw Zegeye
Original Research
The efficient and effective administration of land and its associated resources depends upon the availability of good land information. Many countries are computerising their cadastral records and creating large, national databases. Land-related data are now being integrated, analysed, and distributed in ways that until recently were not possible. In the study area, the existing land management system is carried out in analog format; fully conventional way. Therefore, the purpose of this study is to conduct cadastral information system in GIS environment for the betterment of land management system in the Town. To do this, a detailed GIS-based approach was used to build a geodatabase of spatial and non-spatial data of the study area. The spatial data were added using coordinate geometry (COGO) in GIS environment. The non-spatial data was encoded using key board entry method in Arc Map environment. Then, Graphics were linked with non-spatial attributes data base. Similarly, spatial and non-spatial queries were performed in GIS environment. Some of the operation was, query at owner name, land acquisition type and population density As a result, GIS –based digital cadastral map of Tepi town was produced. The paper revealed that, the system will provide reliable and easy system for collecting information, analysis, retrieval, and monitoring trends pertaining to any particular plot of land which is invaluable for efficient land management in the study area.
Journal of Geosciences and Geomatics. 2019, 7(4), 184-190. DOI: 10.12691/jgg-7-4-3
Pub. Date: July 07, 2019
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by Maju-Oyovwikowhe G E and Imasuen I O
Original Research
A total of eight (8) sandstone samples were subjected to sedimentological and inorganic geochemical analyses in the investigation of reservoir potential, environment of deposition, tectonic setting, and provenance of Campano-Maastrichtian rock units in Anambra Basin, southeastern Nigeria. Sedimentological studies reveal that samples of Owelli and Ajali Sandstones are coarse to medium grained, poorly sorted to moderately sorted sediments deposited in a fluvial environment. The heavy mineral assemblages made up of garnet, epidote and staurolite suggest a metamorphic source while tourmaline and zircon suggest igneous or metamorphic sources. The high maturity indices (58.6 to 71.4) as well as the high percentage of quartz (68 to 74%) suggest mature sandstones that can act as reservoir for generated hydrocarbon. The major oxides discriminate function diagram shows active passive margin for the sandstone samples. Quartzose sedimentary provenance was shown for the sediments which have been highly reworked from original igneous and metamorphic sources, possibly from Abakiliki uplift, Oban massif and/or Obudu basement rocks in the southeast. The high chemical index of alteration (averaging 93%) and the low ratio of K2O/Al2O3 (0.02 to 0.11) in the sediments confirms sedimentary recycling and intensive source area weathering.
Journal of Geosciences and Geomatics. 2019, 7(4), 172-183. DOI: 10.12691/jgg-7-4-2
Pub. Date: July 04, 2019
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by Ukuedojor Kingsley Oghenemeruo and Maju-Oyovwikowhe Gladys Efetobore
Original Research
The reservoir properties of the D-3 sandstone in Idje field of the Niger Delta region had been established. Petrophysical evaluation had been carried out as well as deducing the reservoir geometry. Idje field is an 8.4 km2 area between latitudes 4o31’49”N and 4o33’23” N and longitudes 4o34’43”E and 4o36’17”E offshore Niger Delta in water depth of approximately 1000m on the continental slope. Well logs suites from ten wells comprising gamma ray, resistivity, neutron and density were obtained and analyzed. Petrophysical parameters were derived from which deductions and interpretations were made based on findings. Three sets of correlations were made on the E-W, NE-SW and NW-SE trends to ascertain the geometry of the reservoir. From the result, it was observed that the reservoir was a sedimentary dome possibly resulting from an underlying shale diapir. The log motif range from cylindrical shape with sharp base and top in the western portion to serrated shape in the eastern portion indicating a gradual transition from a slope channel fill (probably submarine canyon) in the proximal west to a distal deep marine slope towards the East. The Vshale range of 0.02 to 0.14 was shown to be for very clean sandstone in the west to slightly shaly sandstone in the east. The reservoir was shown to have a very good porosity and excellent permeability with average porosity value of 0.25 and an average permeability value of 3393.69m. Average hydrocarbon saturation of 48% was observed. Irreducible water saturation was 8% and the average water saturation across the hydrocarbon penetrated wells was 52%. Based on the aforementioned, water would be produced in the field alongside hydrocarbon and therefore possible measures for separation must be employed.
Journal of Geosciences and Geomatics. 2019, 7(4), 157-171. DOI: 10.12691/jgg-7-4-1
Pub. Date: July 04, 2019
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