Geospatial analysis of environmental noise levels in a residential area in Lagos, Nigeria

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

An assessment of seasonal variations in the cref cors at the University of Lagos

Continuously Operating Reference Stations (CORS) are reference stations of the Global Navigation Satellite System (GNSS), providing fundamental positioning infrastructure that is accurate and reliable. As such, CORS are designed to meet the needs of a wide range of users requiring high three-dimensional (3D) positional accuracy. The Continuously Operating Reference Station at the Engineering Faculty (CREF), University of Lagos was set up in order to support research applications in Surveying, Mapping and Geodesy. This study evaluates the seasonal variations in the 3D coordinates of CREF using metrics such as coordinate differences, Standard Deviation (SD) and Standard Error (SE). The Canadian Spatial Reference System (CSRS), known as CSRS – Precise Point Positioning (CSRS-PPP) was used to compute the station’s daily coordinates over a three-year period from 2016 to 2018. In the analysis, the daily coordinates were divided into two seasons - the wet and the dry. The results obtained show that the dry and the wet seasons had SDs (5.4 mm, 3.9 mm, and 2.0 mm) and (5.2 mm, 18.6 mm and 14.4 mm) in the x, y and z-directions respectively. Generally, the dry season presents a better result than the wet season as revealed by the accuracy metrics. These results have led to an increased understanding of the seasonal variability inherent in the data acquired by GNSS CORS, and must be taken into consideration: in particular, for GNSS applications such as the weather prediction and water vapour estimation. This study concludes that more needs to be done regarding the maintenance of CREF to ensure data continuity and reliability for geodetic studies