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The 20 m SPOT DEM (Digital Elevation Model) was acquired by the Office of the Surveyor-General of the Federation (OSGoF) in Nigeria for use in topographic mapping. A localized assessment of the DEM is needed to validate its stated accuracies as it is well-known that the vertical accuracies of global DEMs vary in different landscape contexts. Hence, this study assessed the quality of the DEM in various landscapes and terrain contexts by comparing its heights against 780 Ground Control Points (GCPs) in Lagos State and the Federal Capital Territory (FCT) of Nigeria. The pattern of distribution of the height differences was analyzed using spatial autocorrelation analysis, including other accuracy metrics employed. In the general accuracy assessment, the DEM yielded root mean square errors of 2.33 m in Lagos and 3.69 m in the FCT. It was shown that heights over the bare lands were the most accurately represented on the DEM while heights over built-up areas were the least accurate at both locations. Despite this, the SPOT DEM accuracies in the varying land cover types surpassed its stated global accuracy. Also, Pearson’s correlation analysis revealed no indication that error distribution over the landscape was a function of slope and/or aspect. While the spatial distribution of height differences in Lagos State exhibited randomness, the trend in FCT manifested some spatial clustering. It is recommended that the country should extend the application scope of the DEM to exploit its utility to the maximum.

Lagos State, which is home to Lagos metropolis and the eighteenth largest urban agglomeration in 2018 in the world, has been characterized by rapid urbanization. An earlier study of the eastern segment of the state revealed dramatic urban growth in previously rural local councils where it replaced mostly ecological assets. For a statewide view of the landscape pattern changes, this study examined the western segment of the state to characterize the magnitude and trend of these changes. This was done with Landsat images for 1984, 2006 and 2015 along with ENVI 5.0 software and FRAGSTATS v.4.2 spatial pattern analysis program. Results show that cumulatively, the ecological assets, which comprised 75% of the area in 1984, have been whittled down to about 34% by 2015 having been lost through urban development. At the council level in 2015, the highest growth areas, in decreasing order of magnitude, were Alimosho, Badagry, Ojo and Amuwo Odofin local government areas. Both class and landscape-level metrics confirmed the dominance and fragmentation of the resultant landscape in 2015 by urban development. In 1984, vegetation dominated the landscape at 55% coverage and was the largest feature with the highest area-weighted contiguity or connectedness index. Thirty-one years later in 2015, built-up areas were the dominant patch with 54% coverage and the highest contiguity and area-weighted contiguity index, higher than vegetation. These findings have narrowed the information gap about the spatial and temporal changes in the ecological assets of the western segment of Lagos State as a result of rapid urban expansion.

Gullies and other forms of erosion have been the greatest environmental problem and catastrophe in most high- and low-income countries. The challenge posed by soil erosion has compromised agricultural productivity, environmental biodiversity and food safety for the world's population. It is important to identify vulnerable areas to soil erosion in each region to initiate remedial measures. This study demonstrates the use of watershed morphometry coupled with weighted sum analysis (WSA) to estimate the soil erosion susceptibility of the Imo River Basin sub-watersheds (SWs) in South-Eastern Nigeria using satellite remote-sensing data and geographic information system (GIS) analysis. To this end, Shuttle Radar Topography Mission (SRTM), a Digital Elevation Model (DEM) with 30 m spatial resolution was used to extract and analyse 18 morphometric parameters including basic, linear, shape and relief. The method of receiver operating characteristics (ROC) curves was used to validate the model's prediction accuracy. This morphometry-based analysis resulted in the SWs being classified into zones of low, medium, high and very high erosion susceptibility. With regard to erosion susceptibility, 41.51% of the basin (2494.68 km2) is in the very high priority zone; while 10.50%, 44.33% and 3.66% of the basin are in the high, medium and low priority zones respectively. Validation of the final erosion susceptibility map showed a prediction accuracy of 81%. The use of satellite imagery and morphometric analysis in this study was cost- and time-effective for identifying areas susceptible to soil erosion.

The continuous monitoring of the relationship between land surface temperature (LST) and land cover change is imperative for an inquiry into the potential impact of LST on human well-being, including urban outdoor thermal comfort in Lagos State, Nigeria. Using Landsat imagery, this study assessed land cover and LST changes from 1984 to 2019. Land cover was extracted, LST was determined from Landsat imageries and the land cover changes were linked to LST using the contribution index (CI). Afterwards, the universal thermal climate index (UTCI) was calculated to determine the heat stress levels. Findings confirm the presence of urban sprawl and new growth areas in previously rural Local Government Areas (LGAs) eastward, northward and westward of Lagos metropolis and in regions which lie on the fringe of the state's border with Ogun State. Also, a very strong link between high LST intensities and increasing concentration of urban areas in rapidly growing LGAs has been observed. This link further confirms the increased warming of the state, with an increase in mean LST of 2.16°C during 1984–2019. The UTCI which was used to gauge the influence of LST on outdoor thermal comfort ranged from moderate to strong heat stress levels. This study helps to strengthen the case for definite policies and actions which should be aimed at achieving moderate urban development through increased urban tree canopy/green infrastructure provision and carbon sequestration activities in urban design/landscape design, in Lagos State.

Noise is an inevitable part of daily life and has been identified as a cause of several health deficiencies across the world. It has increasingly become a significant concern on the health and well-being of people. Studies are required to advance knowledge on the sources and impacts of noise in residential neighbourhoods of Lagos State, Nigeria. Therefore, this study assesses the spatial variation of noise levels within a section of the Festac residential area in Lagos in line with noise limits specified by the World Bank Group International Finance Corporation (IFC) Environmental, Health, and Safety (EHS) Guidelines and the Nigerian National Environmental Standards and Regulations Enforcement Agency (NESREA) Noise Standards and Control guidelines for community noise. Data for this research come from a field study comprising measurements of noise levels from 6 observation stations and questionnaire survey with 200 respondents. The criteria for siting the stations was based on factors such as proximity to the roadside, land use and population density, while the questionnaire was administered at random to assess the peoples’ level of awareness on the sources and effects of noise. A digital sound level meter was used to measure noise level variations over a period of 3 weeks for morning, afternoon and evening periods. The measured noise levels were analysed using Analysis of Variance (ANOVA) statistics and the Kriging Geostatistical interpolation technique. Also, logistic regression was used to determine the relationship between the respondents’ perceptions to noise and noise levels. The results indicated that the mean noise levels were within the approximate range of 53.5 – 94.0dBA over the entire period. The highest mean noise levels occurred in the north-western part of the study area where a bus park is present. In general, the noise levels in the area surpass the recommended noise limit of 55dBA, and the logistic regression showed that morning, afternoon and evening mean noise levels were significant predictors of noise variation as perceived by the dwellers. Proper legislation to regulate human activities with respect to noise generation is highly recommended to the local, state and national legislators.

The Lagos Lagoon is under increased pressure from growth in human population, growing demands for natural resources, human activities, and socioeconomic factors. The degree of these activities and the impacts are directly proportional to urban expansion and growth. In the light of this situation, the objectives of this study were: (i) to estimate through satellite imagery analysis the extent of changes in the Lagos Lagoon environment for the periods 1984, 2002, 2013 and 2019 using Landsat-derived data on land cover, Land Surface Temperature (LST), Normalised Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI); and (ii) to evaluate the relationship between the derived data and determine their relative influence on the lagoon environment. The derived data were subjected to descriptive statistics, and relationships were explored using Pearson's correlation and regression analysis. The effect of land cover on LST was measured using the Contribution Index and a trend analysis was carried out. From the results, the mean LSTs for the four years were 22.68°C (1984), 24.34°C (2002), 26.46°C (2013) and 28.40°C (2019). Generally, the mean LSTs is in opposite trend with the mean NDVIs and EVIs as associated with their dominant land cover type. The strongest positive correlations were observed between NDVI and EVI while NDVI had the closest fit with LST in the regression. Built-up areas have the highest contributions to LST while vegetation had a cooling influence. The depletion in vegetative cover has compromised the biodiversity of this environment and efforts are required to reverse this trend.

Lekki Peninsula, which is home to the nouveau riche, is one of the barrier islands of the barrier-lagoon system of the Lagos coastline. The peninsula has been undergoing rapid urbanization since 1980 in total disregard of its physical characteristics. This study assessed landscape dynamics in the peninsula from 1984 to 2014 and evaluated risks to development from potential storm surge flooding. The datasets included baseline data on geographical indicators/island characteristics, satellite imageries and ancillary data. Storm surge flooding hazards and areas at risk were assessed in a Planar GIS environment and with two-dimensional (2D) hydrodynamic simulation using the Cellular Automaton Evolutionary Slope and River (CAESAR) model. Results reveal that the Lekki Peninsula which was a green zone had grown from about 0.5% built-up area in 1984 to about 18% built-up area in 2014. This growth was due to urban expansion and occurred mostly in areas of ecological assets including mangroves, swamps and vegetation. The highest growth in built-up area occurred in Eti-Osa Local Government Area (LGA). Generally, the peninsula has a low-lying topography with 37% of its area lying between 0.5 m and 3 m while 63% is between 3 m and 5 m above mean sea level. Potential inundation simulation with the CAESAR model for selected storm surge levels reveal that at surge heights of 4 m and 5 m, 25% (mostly in Eti-Osa) and 37% respectively of the peninsula are flooded with the latter choking off Epe Expressway on both ends. Initial ingress of inundation occurred in Eti-Osa LGA. In comparison to Planar GIS water levels, the CAESAR model reflected more realistic flood extents. The base flood elevation (BFE) and design flood elevation (DFE) are recommended to improve the sustainability and resilience of future developments along with the recognition of natural processes in future policy and development of the peninsula.

The Nigerian Geodetic Reference Frame is defined by a number of Continuously Operating Reference Stations (CORS) that constitute the Nigerian GNSS Network (NIGNET). NIGNET is essential for planning and national development with the main goal of ensuring consistency in the geodetic framework both nationally and internationally. Currently, the strength of the network in terms of data reliability has not been adequately studied due to the fact that research into CORS in Nigeria is just evolving, which constitutes a limitation in its applications. Therefore, the aim of this research is to explore the reliability of the 3-dimensional coordinates of NIGNET to inform usability and adequacy for both scientific and practical applications. In particular, this study examines if the 3-dimensional coordinates of NIGNET are equally reliable in terms of positional accuracy. Accordingly, this study utilised GNSS data collected over a period of six years (2011 – 2016) from the network to compute the daily geocentric coordinates of the stations. Exploratory and statistical data analysis techniques were used to understand the magnitude of the errors and the accuracy level in the 3-dimensional coordinates. For this purpose, accuracy metrics such as standard deviation (𝜎), standard error (𝑆𝐸) and root mean square error (RMSE) were computed. While One-way ANOVA was conducted to explore the coordinate differences. The results obtained showed that SE and RMSE ranged from 13.00 − 56.50𝑚𝑚 and 14.38 − 73.16𝑚𝑚 respectively, which signifies high accuracy. Overall, while 88% of the network showed a high level of positional accuracy, the reliability has been compromised due to excessive gaps in the data archiving. Therefore, due attention must be given to NIGNET to achieve its purpose in the provision of accurate information for various geospatial applications. Also, any efforts directed at understanding the practical implications of NIGNET must be well-embraced for the realization of its set objectives.

Unmanned Aerial Vehicles (UAVs), commonly known as drones are increasingly being used for three‑dimensional (3D) mapping of the environment. This study utilised UAV technology to produce a revised 3D map of the University of Lagos as well as land cover change detection analysis. A DJI Phantom 4 UAV was used to collect digital images at a flying height of 90 m, and 75% fore and 65% side overlaps. Ground control points (GCPs) for orthophoto rectification were coordinated with a Trimble R8 Global Navigation Satellite System. Pix4D Mapper was used to produce a digital terrain model and an orthophoto at a ground sampling distance of 4.36 cm. The change detection analysis, using the 2015 base map as reference, revealed a significant change in the land cover such as an increase of 16,306.7 m2 in buildings between 2015 and 2019. The root mean square error analysis performed using 7 GCPs showed a horizontal and vertical accuracy of 0.183 m and 0.157 m respectively. This suggests a high level of accuracy, which is adequate for 3D mapping and change detection analysis at a sustainable cost.

Introduction:the spread and diffusion of COVID-19 undoubtedly shows strong spatial connotations and alignment with the physical indices of civilization and globalization. Several spatial risk factors have possible influence on its dispersal trajectory. Understanding their influence is critical for mobilization, sensitization and managing non-pharmaceutical interventions at the appropriate spatial-administrative units. Methods:on 01 April 2020, we constructed a rapid spatial diagnostics and generated vulnerability map for COVID-19 infection spread at state level using 12 core spatial drivers. The risk factors used include established COVID-19 cases (as at 01 April 2020), population, proximity to the airports, inter-state road traffic, intra-state road traffic, intra city traffic, international road traffic, possible influx of elites from abroad, preponderance of high risk political elite, likelihood of religious gathering, likelihood of other social gatherings, and proximity to existing COVID-19 test centers. These were also tested as predictors of COVID-19 spread using multiple regression analysis. Results:the results show that 6 States - Lagos, Kano, Katsina, Kaduna, Oyo and Rivers - and the Federal Capital Territory have very high vulnerability, 17 states have high vulnerability and 13 states have medium vulnerability to COVID-19 transmission. Several drivers show a strong association with COVID-19 with the coefficient of correlation ranging from 0.983 - 0.995. The regression analysis indicates that between 96.6 and 99.0 percent of the total variation in the COVID-19 infections across Nigeria can be explained by the predictors. Conclusion:the spatial pattern of infection across the states are substantially consistent with the predicted pattern of vulnerability.

Land Surface Temperature (LST) is one of the key environmental parameters affected by land cover change. Lagos State has been experiencing an increase in surface temperature due to growing areas of impervious surfaces caused by anthropogenic urban sprawl. While the change in LST has been established, its continuous monitoring and relationship with continuing Land Cover (LC) changes have become imperative for appropriate management and policy actions. This study investigated the effect of land cover change on LST in the rapidly urbanising Lagos metropolis. Using spatio-temporal Landsat imageries with their thermal bands and ancillary data, land cover and LST changes were assessed from 1984 - 2015. The spatial patterns of LST and LC were derived to examine the response of LST to urban growth. Findings confirmed urban sprawl in previously rural areas northward of the metropolis in LGAs such as Ikorodu, Kosofe and those fringing the state’s border with Ogun State. This also confirmed new growth areas as occurring west of the metropolis in Amuwo-Odofin LGA. The results further showed that the rapid urbanisation in Lagos metropolis has altered the surface thermal environment as indicated by increased LST. Built-up area and bare land accounted for the highest increase in LST (as high as 1.5℃ in some areas) while wetlands and other vegetated areas played a vital role in moderating the surface temperature in areas they still occupy. This provides reasonable evidence for the appropriate authorities to institute requisite policies and actions towards moderating urban sprawl while ramping up the development of urban green infrastructure to counter global warming.

It has been established that women spend more time in the neighbourhood environment, and therefore, are more vulnerable to the observable poor conditions. The focus of this study is on neighbourhood environmental stressors that affect womens’ health in Lagos metropolis. The factors considered include access to clean water, adequate sanitation, drainage conditions, ventilation and hygiene, type of energy for cooking and nutrition. These factors are exacerbated by poverty and differ across different neighbourhoods in Lagos metropolis. 1150 respondents (high – 50; medium – 328; and low - 772) consisting of randomly selected women, aged 18 years and above were selected from all the 17 Local Government Areas (LGAs) in metropolitan Lagos to achieve 100% representation. Focus Group Discussions were held with women from selected different neighbourhoods. A 5-point likert scale was used as a measure of self-reported stress and self-reported health, with higher numbers indicating a greater self-reported stress. From the different survey methods used, results show that women in the low income neighbourhoods are more vulnerable to environmental stressors, and so their health is mostly affected negatively. Women in the other income groups also experience some form of stress but at lower severity levels. Environmental stressors and severity of chronic illness are linked to stress. An improvement in the environmental conditions will reduce the amount of stress experienced by women of different income neighbourhoods.

Structural trends in the earth's crust can be detected in the form of lineaments and may be useful in several environmental applications such as mineral exploration and hydrogeology. In this study, structural lineaments in the western sector Gongola basin of Northern Nigeria were mapped using two approaches - the analysis of gravity data and the processing of Landsat 8 imagery. In the analysis of gravity data, a convolution was done between the Fourier kernel obtained from the Second Horizontal Derivative of the Truncated Horizontal Plate and the gravity anomaly. The lineaments were extracted as the sharp gradients in the second horizontal derivative map. The NE-SW and E-W trending lineaments were interpreted as fault (strike-slip wrench) systems. In the second approach, a 5 × 5 directional filter was applied to the Landsat imagery in the N-S, NE-SW, E-W and NW-SE directions. Next, edge detection, thresholding and curve detection were done to extract the lineaments. It was observed that the NW-SE and NE-SW lineaments correlate more with the lineaments/faults in the gravity maps. Comparison of rose diagrams of lineaments as obtained from the remote sensing method shows a high correlation with the major linear structures in the study area. High correlation exists between lineaments delineated from remote sensing and gravity data. Result from the lineament analysis shows that groundwater potential is high in the areas with high lineament density. Settlements such as Mallurin Tudu Yautare, Wuro Bundu, Kunde and Tauya which are located in the northern part of the basin have high groundwater potential due to the high lineament density from the gravity and the remote sensing methods. Lafiya and Jimbom communities located in the south eastern part of the basin also have high lineament density which signifies good groundwater potential. These results have demonstrated the advantage of remote sensing for detecting lineaments in support of groundwater mapping. This good correlation between lineaments mapped from both methods enables the lineaments to be regarded as representative of the structural manifestation of the Gongola Basin. This can serve as a reconnaissance approach to aid more precise geophysical observation.

Uyo City in Akwa Ibom State, Nigeria has experienced rapid urban growth and development over the past decades. The urban expansion has led to different land cover transitions which in turn have caused significant changes in key environmental parameters such as Land Surface Temperature (LST) and Normalised Difference Vegetation Index (NDVI). This study investigated land cover changes in Uyo and the relationship with LST and NDVI. Landsat multispectral imageries covering the study area were acquired for three periods – 1986, 2000 and 2018. Land cover was extracted using the Maximum Likelihood Classification (MLC) technique, LST was derived using a single channel algorithm applied on the imagery thermal bands, and the NDVI equation was applied to the imageries. To assess the MLC accuracy, four different accuracy metrics were calculated – user's accuracy, producer's accuracy, overall accuracy, and kappa coefficient. Change statistics were computed to evaluate the transition dynamics of each land cover class. Finally, the relationship between land cover, LST and NDVI was evaluated using the Contribution Index (CI) and Pearson's Correlation analysis. Between 1986 and 2018, vegetation declined from 278 km2 to 219 km2, wetlands declined from 20 km2 to 17 km2, barren land declined from 33km2 to 25km2 while built-up areas increased from 69 km2 to 139 km2. There were significant transitions in land cover for instance, 78km2 of vegetation and 14km2 of barren land were converted to built-up area over the 32 years. The mean LSTs in the city were 21.67 °C (1986), 25.40 °C (2000) and 26.04 °C (2018). The highest contribution to LST was from built-up areas while the lowest was from vegetation. The CI of built-up areas rose from 0.08 in 1986 to 0.30 in 2018, Similarly, LST profiles showed that the diffusion of higher LSTs across the study area was in tandem with the horizontal expansion of built-up areas. There was also a high negative correlation between LST and NDVI at the three periods of study. It is recommended that the Uyo local authorities take deliberate measures and policies aimed at moderating urban growth while ensuring the conservation of urban greens spaces in the city.

Geospatial visualisation presents us with innovative techniques of assessing uncertainty in digital elevation datasets. It gives the viewer immediate feedback on potential problems and heightens understanding of effects not easily appreciated when dealing with numerical statistics only. This study evaluated the performance of 30-metre resolution SRTM version 3.0 and ASTER GDEM version 2 over Lagos, Nigeria. Both datasets were examined by direct comparison with 176 highly accurate Ground Control Points (GCPs) coordinated by GPS (Global Positioning System) observation. The basis of comparison was on the elevation differences between the Digital Elevation Models (DEMs) and the GCPs at coincident points. The performance of both DEMs was visualised in 2D and 3D space by comparing pixel values and surface models. In the assessment, the absolute vertical accuracies of SRTM v3.0 and ASTER v2 are 4.23m and 28.73m respectively. The accuracy of SRTM for the study site proved to be higher than the value of 16m presented in the original SRTM requirement specification. ASTER did not meet up with its 17m overall accuracy specification. KEYWORDS : Uncertainty, Visualisation, Digital Elevation Model, SRTM, ASTER.

International audience; Satellite-derived Digital Elevation Models (DEM) are fast replacing the classical method of elevation data acquisition by ground survey methods. The availability of free and easily accessible DEMs is no doubt of great significance and importance, and a valuable resource in the quest to accurately model the earth's surface topography. However, the suitability of Digital Elevation Models in simulating the topography of the earth at micro, local and regional scales is still an active area of research. The accuracy of Digital Elevation Models vary from one location to another. As such, it is important to conduct local and regional assessments to inform the global user community on the relative performance of these DEMs. This study evaluates the accuracy of the 30-metre Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Models version 2, the 1-kilometre GTOPO30, the 90-metre Shuttle Radar Topography Mission v4 and the 1-kilometre Shuttle Radar Topography Missionv2.1 Digital Elevation Models by validating with highly accurate GPS check-points over Lagos, Nigeria. With a Root Mean Square Error of 3.75m, the results show that Shuttle Radar Topography Mission v4 has the highest vertical accuracy followed by Shuttle Radar Topography Mission v2.1 (Root Mean Square Error: 5.73m), Advanced Spaceborne Thermal Emission and Reflection Radiometer (Root Mean Square Error: 21.70m), and GTOPO30 which shows the lowest vertical accuracy (Root Mean Square Error: 29.41m). By conducting the accuracy assessment of these products in Lagos, this study informs efforts directed at the exploitation of these Digital Elevation Models for topographic mapping and other scientific and environmental application.

As a pivotal infrastructure for the socio-economic development of Nigeria, the Nigerian Global Navigation Satellite Systems (GNSS) Reference Network – NIGNET – can serve as a tool for weather and climate monitoring, by obtaining and analyzing the neutral atmospheric Zenith Total Delays (ZTD) from processed GNSS data. With the use of surface meteorological measurements, the ZTD can be transformed to the integrated water vapor content in the neutral atmosphere, which is an essential parameter in weather forecasting, and climate change and variability analysis. The focus of this research is to assess the adaptability of the NIGNET for meteorological applications using the global positioning system precise point positioning (PPP) derived ZTD at the stations. ZTD estimates are derived from daily data obtained from the NIGNET and International GNSS Service (IGS) stations spanning the years 2011–2016. These estimates are compared with ray-traced delay estimates from the National Centre for Environmental Prediction Reanalysis II (NCEP II) global Numerical Weather Model (NWM) and the IGS zenith path delay products. A comprehensive analysis is performed to assess the level of agreement of the different ZTD estimates and to identify possible systematic effects from the different sources. Comparisons between the PPP and NCEP II NWM ZTD estimates show a range of mean offsets from −6.4 to 23.9 mm, and standard deviations from 33.1 to 44.9 mm. With the PPP and IGS ZTD estimates, mean offsets of −2.4 and −0.1 mm, and standard deviations of 9.9 and 13.8 mm are obtained.

Lagos metropolis, the current economic capital of Nigeria is a low-lying coastal city endowed with a number of lagoons and wetland ecological assets. Lagos/Lekki Lagoons being the largest with a combined size of 646km2 are fringed on many sides by wetlands. Many of these wetlands have undergone severe spatial changes from rapid urbanization in the past three decades. The precise nature of these changes is largely unknown and unreported. As the area is experiencing intense development pressure, this study therefore examined the spatial changes in the wetlands fringing these lagoons using the integrated approach of remote sensing data and GIS with topographic maps providing baseline data. The objective is to quantify and establish the precise location and magnitude of these changes over the years from 1984 to 2006. Two types of wetlands are prevalent in the Lagos area namely: the swamps and mangroves. ENVI software was used along with parallelepiped supervised classification in processing the Landsat images. Results show that the mangrove wetlands decreased from 88.51km2 to 19.95km2 at -3.12km2 annually while swamps decreased from 344.75km2 to 165.37km2 at - 8.15km2 annually both between 1984 and 2006. Results further show that mangroves which were widespread in seven council areas around these lagoons in 1984, have dwindled to only four councils in 2006. These decreases are attributable to urban development pressures. Some of the implications of these losses and conservation issues are briefly highlighted.

Determination of height information using the classical field surveying and geodetic methods is rather expensive, rigorous and time consuming. It is also limited in the capacity of the earth surface data gathered. These conventional topographic mapping technologies have produced maps with a variety of scales and of uneven quality - some with astounding accuracy, some far less adequate. A good alternative is the Shuttle Radar Topography Mission (SRTM) derived Digital Elevation Model (DEM) which provides an excellent base data for extracting heights for topographic mapping. This will ameliorate the present situation. The SRTM space mission produced the most complete, highest resolution digital elevation model of the Earth. This study is aimed at developing a model for the transformation of the SRTM heights from WGS84 datum to the Nigerian height system (Minna datum) using SRTM derived DEM, topographic map and Global Positioning System (GPS) data of some parts of Lagos state, Nigeria. The chosen site corresponds to the area covered by one map sheet at the scale of 1:25,000 (13.8km x 13.8km) which is 190.44sq.km. Software such as Globalmapper, Surfer 8.0 and ArcGIS 9.3 were used for specialized data processing and analysis. However, the datasets obtainedwere first projected to a common system and subsequently harmonized. This was carried out with an overlay of GPS points on the grid based SRTM and topographic DEM surfaces of the environment. Results showed deviation in heights with coinciding planimetry data. The average absolute error of the SRTM DEM for our test site was gotten as +/-0.22087m. Finally, by modelling this vertical shift, a transformation model that is accurate with a standard error of 0.238m was developed.

Obiefuna, J.N.; Nwilo, P.C.; Atagbaza, A.O., and Okolie, C.J., 2013. Land cover dynamics associated with the spatial changes in the wetlands of Lagos/Lekki Lagoon system of Lagos, Nigeria. Urban sprawl is one of the severe land use/land cover (LULC) change agents, especially in rapidly urbanizing developing countries such as Nigeria. Land use/land cover is among the key drivers of environmental change as it leads to dramatic changes in both landscape patterns and ecosystem functions. Lagos metropolis, the nation's economic nerve center, is on a low-lying coastal landscape endowed with lagoons, wetlands, and other ecological assets. The Lagos/Lekki Lagoon system, with its catchments and wetlands, constitute about 71% of the state. With rapid urbanization and intense development pressure, some of the fringing wetlands and other land cover in the area have been converted to urban landscape. Just like the wetlands, the precise nature of these land cover changes is comprehensively unknown. In this ong...