Geodesy and Geomatics

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3D Gravity Inversion for Mineral Exploration Over Southern Green-stone-Belts of Ethiopia
(Addis Ababa University, 2022-03) Girum, Ashenafi; Tulu, Besha (PhD)
Mainly this study aimed to investigate subsurface geology of the southern green stone mineralization zone for evaluation of gravity inversion is how effectively detecting high-density mineralization. Throughout the project, three main tasks have done: the first task was carrying out necessary correction for observed gravity data. Under this stage three main outputs were obtained: Bouguer gravity anomaly, regional Bouguer anomaly and residual Bouguer anomaly. The target information is represented by residual anomaly therefore it is became the final data for inversion process. The second task was minimizing Tikhonov’s cost function and carrying out inversion with the help of a conjugate gradient algorithm after formulated sensitivity matrix. The interpretation process was the last step of the work. The results obtained from the inversion process are demonstrated in two forms: the first one was a horizontal slice that illustrated the trend of mineralization in a horizontal plane and the second was density contrast model in a vertical plane that illustrated at four different lines of cross-section. In the horizontal density contrast model, the pixels value of high-density contrast under mineralization zone revealed 76.8% of pixels made a good agreement with the mineralization history of the target region. In addition, 90.3% of high-density contrast agreed with the location of metallic minerals in the region. In contrast, very low-density contrast in the region scored 3.77%. Therefore the inverted density contrast model well demonstrated the signature of mineralization in the target region. The vertical slice of the density contrast model indicated the depth condition of the high anomalous density region. Thus cross-section profile 1 up to 4 maximum depth and percentage of high density contrast above 600m depth are 1309.464m, 1089.866m, 847.72m, 661.0338m and 81.5%, 72%, 86.3%, 99.1% respectively. The vertical patterns of high-density contrast are correlated with the information obtained from a borehole at the mineralization zone. From such results and validation, I concluded: gravity anomaly inversion is a good tool to detect the position, depth extent, and the trend of the significant anomalous region.
A gravimetric method to determine horizontal stress field due to flow in the mantle in East Africa Great Rift Valley
(Addis Ababa University, 2023-07) Abenezer Getinet; Andinet Ashagire (Phd)
The gravimetric approach has been widely used to determine the stress field of subsurface geology of the earth crust. Mainly this study aimed to determine lithospheric shear stress in the Earth’s mantle and its temporal changes caused by geodynamical movements. The gravimetric approach is applied, to evaluate the stress at the base of lithosphere and to detect changes in stress using static gravity field model EGM08 and GRACE monthly solutions respectively. In addition to the static gravity field data some physical information about topographic height, crustal thickness, and lithospheric thickness are incorporated in this method. As a result, more geophysical information and data are applied for computation of horizontal lithospheric stress in this approach. To do so, depth of the base of lithosphere determined by subtracting topographic height from lithospheric thickness is needed, thus the lithospheric shear stress component computed at the base of lithosphere. Moreover, the comparison of lithospheric shear stress using different static gravity field models are performed. The estimated horizontal shear stress at the base of the lithosphere throughout the study area revealed 55.68% of the stress is oriented in a northward direction and the remaining 44.32% is oriented in the southward direction; 44.41% of the stress is oriented in an eastward direction and the remaining 55.59% is oriented in the westward direction: and the result of the estimated horizontal shear stress magnitude ranges from ≈ 0.04 MPa to ≈ 15.32 MPa. Furthermore, the estimated horizontal shear stress components show good agreement with the tectonic boundaries and the location of stress regimes in the WSM2016 database, as well as the seismic events in the study area.
Accuracy assessment and bias correction for open sources Digital elevation model (DEM): a case study in and around Diredawa city, Ethiopia
(Addis Ababa University, 2022-02) Mesfin, Delelegn; Tulu, Besha (PhD)
Digital elevation model (DEM) is a digital and mathematical representation of the real-world topographic surface by using elevation data. The global open-access DEM data contain errors and are not suitable for engineering and other high accuracy requiring applications. The main aims of this study are vertical accuracy assessment and bias correction for open-source global DEM data. Conventional global DEM data; SRTM DEM 1-arc second and ASTER-GDEM 1-arc second, and new global DEM data ALOS-PALSAR both 12.5 m and 30 m spatial resolution DEM data were applied for this study. Ground control point GCP, RTK-GPS data, and photogrammetric DEM reference data were used to evaluate the accuracy of the selected open-source global DEM data. Accuracy assessment was applied in different approaches, one is a point-based approach using statistical measurement. The computed Root mean square (RMSE) for SRTM is 3.68 m, 4.24m, and 3.41m in GCP, RTK-GPS, and Photogrammetric DEM reference data, for ASTER-GDEM the RMSE value is 8.87 m, 7.08 m, and 7.05 m, for ALOS-PALSAR12.5 m it is 4.58 m, 4.46 m and 4.58 m and for ALOS- PALSAR30 m the value is 5.79 m, 5.10 m and 5.34 m, respectively. The accuracy of SRTM showed better in three reference data and ALOS-PALSAR12.5 m is followed the SRTM in the accuracy. Whereas the accuracy of ASTER-GDEM showed less accuracy among the selected global DEM data. The second approach is based on land use land cover data using RTK-GPS reference data; bare land, road line, drainage pattern, rock area, and tree areas point data are collected using TRIMBLE R8 GNSS/R6/5800 instrument, the accuracy of rock area showed less accuracy in all DEM data except SRTM DEM and the accuracy of the bare land area showed better in all DEM averagely. And the third approach of vertical accuracy assessment is terrain classification; the terrain of this study area is segmented into three classes (flat area, moderate slope, and steep slope), the accuracy of the flat area showed high and the accuracy of the steep slope is less for all DEM data. Finally, bias correction was applied using linear transformation parameters to reduce the residual of the global DEM data, the accuracy of ASTER-GDEM was improved by 22.9 % after the bias correction, while the accuracy of SRTM is improved by 6.7 % and the accuracy of PALSAR12.5m and PALSAR30 m was improved by 5.1 % and 2.2 % after the bias correction.
Accuracy Assessment of Digital Surface Model from Aerial Images: Case Study of Nifas Silk Sub City, Addis Ababa
(Addis Ababa University, 2022-03) Jemal, Endrie; Andenet, Ashagrie (PhD)
Airborne aerial photograph is one of the most effective means of terrain data collection. The vertical accuracy of DSM derived from 2010 and 2016 collected aerial photograph in urban area of Nifas Silk sub city is the critical point in this research. In this study, the reference level produced from GPS elevation, existed GCP elevation and differential leveling are measured to assessed the vertical accuracy of existed GCP elevation and both DSM elevation data derived from Airborne aerial photograph for building urban land cover types. Using static GPS elevation as a reference, the accuracy of existed GCP elevation gave a RMSE value of 1.049m and an arithmetic mean value of 1.049m. GPS reference elevations gave us the RMSE value of 0.592m and 0.787m and an Arithmetic Mean value of 0.466 and 0.659 for used DSM derived from 2010 and 2016 aerial photograph respectively. On the other hand, by using GCP as reference elevation, gave the RMSE value of 0.415m and 0.486m and also used differential leveling elevation, gave the RMSE value of 0.68m and 0.911m for used both DSM derived from2010 and 2016 aerial photograph respectively. A spatial analysis tools can be used for the extraction of DSM elevation in arc GIS software package. Finally, 1.96xRMSE and frequency histogram statistical measurements of data analysis are performed for the difference between measured independent checkpoints and corresponding point of both DSM derived from the two aerial photographs. For our study area, using the three reference elevation point of existing GCP, RTK GPS and Leveling measurements, DSM derived from (2010) aerial photograph elevation data have an accurate by A RMSE value of ±0.071m, ±0.198m and ±0.231m and/or Absolute Mean value of ±0.071m, ±0.198m and ±0.379m that of the value of DSM derived from (2016) aerial photograph data respectively.
Accuracy Assessment of Geospatial Data for Cadastral Application: A Case of Addis Ababa City, Ethiopia
(Addis Ababa University, 2022-07) Melese Wondatir; Getachew, Tesfaye (PhD)
Datum transformation is the transformation of coordinate points from one known coordinate reference system into another. The recent practice of geospatial data collection, management, and analysis in Ethiopia is in geocentric coordinates of a point defined based on a global datum (WGS84). However, Ethiopia uses Adindan as the recognized local datum. The current official transformation parameters in use by Ethiopia are slightly different from the parameters determined by previous research and adopted in widely used geospatial software packages. In addition to this, the rotation and scale changes are ignored in the transformation parameters. The current practice of cadaster in Addis Ababa city is below the accuracy level of all local and global geospatial data standard guidelines. The main purpose of this study is to assess and evaluate the Accuracy Assessment of Geospatial Data for Cadastral Application: A Case of Addis Ababa City, Ethiopia. Statistical analyses have been done for second-order GCP, orthophoto, and cadastral parcel accuracy assessment analysis based on ASPRS 2014 standards. The positional accuracy of second-order ground control points, orthophoto, and cadastral parcels evaluated by checkpoints is determined as 0.47m, 1.326m, and 1.87m respectively at a 95 % confidence level. Finally, the software packages used to convert from global to local reference datum differ from one another, causing major changes in the values of specific points. Coordinates values of Orthophoto and static GCPs were converted from WGS84 to Adindan using (X = 162m, Y = 12m, and Z = -206m); the RMS error of easting and northing values were 0.32 m and 0.69 m respectively. On the other hand, the static GCPs coordinates were converted by using (X = 165 m, Y =11 m, and Z = -206 m) and compared with orthophoto coordinates, the RMS error of easting and northing values were 2.65 m and 0.78 m respectively. And, according to Molodensky-Badekas seven transformation parameters using (169.674 m in X, 14.801m in y, and -204.841 in Z), the RMS error of easting and northing values were 3.055m and 0.697 m respectively. Finally, the researcher recommends these parameters shall utilize as unique and constant values to improve data integrity for geospatial work such as cadastral application.
Agricultural Land Suitability Analysis Using GIS and Remote Sensing Techniques: The Case of Mecha Woreda, Amhara, Ethiopia
(Addis Ababa University, 2024-01) Abebe Negussie; Hamere Yohannes (PhD)
Agricultural land suitability study plays a vital role in determining forthcoming agricultural cropping patterns, as well as in the formulation of plans and activities related to agriculture. The assessment of land suitability is a critical endeavor that involves the evaluation of a specific area to ascertain its appropriateness and suitability for a particular use within a given locale. This process encompasses a comprehensive analysis that takes into consideration a multitude of factors, including soil characteristics, climate conditions, topographical features, and the availability of water resources. This analysis on land suitability employs a multi-criteria analytical approach in order to determine the most appropriate land for rain-fed purposes. The results of this analysis demonstrate that a considerable proportion of the region being examined exhibits a high level of suitability for agricultural activities. Approximately 20.92% of the region can be designated as significantly suitable for agricultural practices, and an additional 33.03% can be described as highly suitable. These statistics reveal that around 54% of the entire area possesses a substantial capacity for prosperous farming endeavors. According to the research's discoveries, a substantial segment of the evaluated territory is either highly suitable or very high suitable for irrigation, with a combined total of 82.66%.However, there are also notable areas that are only moderately or low suitable (13.96% combined), while a smaller proportion is not suitable (3.38%) for irrigation purposes In conclusion, the results suggest that a significant proportion of the region being examined exhibits a considerable level of suitability, ranging from high to extremely high, for agricultural purposes.
Analysis and Parametric Study of Deep Excavation With Diaphragm Wall Using Finite Element Based Software
(Addis Ababa University, 2010-06) Fekadu, Tewodros; Teferra, Alemayehu ( Profasser)
Control of soil deformation is crucial for deep excavation in congested urban areas to minimize its effect on adjacent structures. Therefore, an analysis and parametric study is important to realistically represent the response of the soil to excavation and to predict the magnitude and pattern of ground movement. This thesis presents a study of the effects of deep excavations with tie back diaphragm wall in expansive clay and red silty clay which are located in Bole Medehanealem area and Arada respectively, and also in cohesionless granular sandy soil. The objectives of this study are to investigate the effect of different parameters on the prediction of ground movement by numerical analysis and to develop a method of estimating these effects quantitatively. Extensive review of relevant literature published in the past four decades was conducted in order to understand the trends and the key developments in this area. It was revealed from the literature review that the concurrent use of the observational method and the finite element method for monitoring and controlling of ground deformations around the excavation has become a norm for deep excavation projects. Parametric studies were carried out to identify important variables controlling the mechanisms of soil-structure interaction. The analyses focus on deep excavations supported by tie-backed diaphragm walls using techniques of top down construction. Exact site conditions and input parameters for the soil were incorporated as much as possible. The principal parameters considered in the study include soil type, depth of excavation, wall embedment depth, wall stiffness, and strut spacing. These variables were used to conduct a series of finite element analyses using simplified geometry and ground conditions for the purpose of achieving the objective of this thesis. Results of these analyses were recorded in terms horizontal displacement of the diaphragm wall, ground settlement behind the diaphragm wall, and bending moments induced in the diaphragm wall due to an adjacent deep excavation.
Analysis of The Inter-Dyking Deformation Pattern at The Ongoing Dabbahu-Manda Hararo (Afar) Rift Segment Using GPS and InSAR Techniques
(Addis Ababa University, 2013-07) Adem, Esubalew; Lewi, Elias(PhD)
The Afar Depression, in the northeastern part of Ethiopia, offers unique opportunities to study the transition from continental rifting to ocean floor spreading. This process, which is the outcome of tectono-magmatic events, has been under investigation using different geophysical and geological techniques. The current study mainly focused on GPS and InSAR methods to analyze the inter-dyking deformation pattern along the Dabbahu-Mnada Hararo (Afar) rift segment. The InSAR data was used to identify the time of dyke events and the GPS data to study the inter-diking deformation pattern. A sequence of 12 dyke events occurred from June 2006 to June 2009 and based on the GPS data two major pattern of deformation have been identified. These are being categorized into before and after June 2009 dyke events. Most of the GPS stations before June 2009 showed larger displacement rate whereas after June 2009 intrusion, the displacement in most of the stations was relatively smaller. Even though the deformation process is still active, sites such as DAFT, DA45, DAYR and DATR indicated that the displacement rate is relatively stabilizing in the post seismic relaxation period. Moreover, sites such as, DA25 and DA35, had large offsets in their time series right at the time of dyking events, which is an indication of major deformation due to the rifting process. Except the distant sites DA60 and DASM all the other stations were mostly affected by the dyke intrusion, such that there was an offset in the data during the dike intrusion. Stations DA25, DA35, DA45, DA60, DAFT and DAYR that are located in the west side of the rift, where the 2005 diking event took place, showed displacement as large as ~84mm/yr, ~53mm/yr, ~46mm/yr, ~17mm/yr, ~23mm/yr,~17mm/yr and ~6.36mm/yr towards the west direction respectively. Sites DASM, GABH and DABB have a displacement towards the North East direction. The site GABH, which is situated in Gabh’o volcano, shows rapid inflation from January to June (2006) and continued with a slow uplifting till February 2007. Inflation began in June 2006 in the composite volcano DABB site while subsidence that amount of about 16mm/yr is observed in Semera station called DASM. Key words: Afar, Deformation, Inter-Dyking, InSAR, GPS, Rifting
Applying 3D-Eco Routing Model to Reduce Environmental Footprint of Road Transports in Addis Ababa city.
(2019-10) Seifu, Woldemichael; Daniel, Alemayehu (PhD)
Road Transportation is the fastest growing major contributor to global climate change, accounting for a significant share of worldwide energy-related carbon dioxide CO2 emissions. It is therefore, this sector needs to undertake responsibilities for its environmental impact. This paper introduces a 3D Eco -Routing Model to reduce environmental footprints of road transports in Addis Ababa city for distribution vehicles, which adds one more degree of freedom to the system and allows driving routes to be optimized for minimum fuel consumption. The applied model in this study takes into account the effects of road inclination, varying velocity, and vehicle weight to evaluate the effects of road inclination on a vehicles fuel consumption and its proportional CO2 - Emissions, the 3D -Routing-Model is applied in three different scenarios within different vehicle weight range in the city of Addis Ababa, political capital of Africa, The obtained results indicate that eco-routes can yield significant fuel and CO2 Reduction potentials of up to 39.818% in the tested scenarios in addition from other pollutants eco routes saves emissions up to 25.650% in the tested scenarios. These numbers designate the importance of considering the topographic characteristics and fuel consumption in routing applications to reduce vehicles emission impacts on the environment. These findings have implications for future investment and policy decisions to concern eco routing strategies.
Assessing the Effects of Land Surface Temperature on Vegetation Cover Change Using Geographic Information System and Remote Sensing Techniques: A Case Study of South Gonder, Ethiopian
(Addis Ababa University, 2021-11) Muluye, Engdaw; Tulu, Besha (PhD)
To assessed remotely data remote sensing and GIS methods was basic to accuse and analysis of the thematic area, like the impacts of vegetation cover change of land surface temperature. But there is a problem on calculating and evaluating the influence of change in vegetation cover on the change of climate. Then, this study was conducted the impacts of vegetation cover change on land surface temperature using remote sensing and GIS methods. The study area was in south which is high populated and more highland. Data was extracted from land satellite images like Landsat 5, Landsat 8 Operational Land Imager/ Thermal Infrared Sensor (OLI/TIRS). Thematic Mapper Sensor (TM) and Climate Moderate Resolution Imaging Spectroradiometer (MODIS) (and also ground truth data was used to verify remotely sensed data, additionally Pearson Correlation coefficient was conducted to calculate and to analyze the relationship of vegetation cover with LST. The final output presented that vegetation cover occupied an area of 227979.09 ha (15.6%),154424.43 ha (12.5%), and 195231.59 ha (13.3 %) in 1985, 2000 and 2018, respectively where 3.1% of vegetation cover has been lost in the last 33 years in in the study area.
Assessing the impacts of urbanization on agricultural land using Remote Sensing and GIS techniques: The case of Adet town, Ethiopia
(Addis Ababa University, 2023-06-16) Yechale Mulu; Asnake Mekuriaw (PhD)
Urbanization was one of the main problems that threaten the limited highly fertile and very productive agricultural land in the periphery of Adet town for residential construction and its related infrastructure. The general objective was to assess the impacts of urbanization on agricultural land using remote sensing and GIS techniques and within it classified the land use land cover dynamics during the time periods of 2000, 2010 and 2020, mapped horizontal expansion of urban boundary and analyzed its effect on the surrounding agricultural land and identified the major trigger factors for horizontal expansion. By using Landsat satellite images generated change detection analysis and mapped horizontal expansions in this particular study. Additionally conducted interviews and identified the trigger socio-economic contributing factors of horizontal expansion. The supervised classification algorithm and Anderson (1976) land use/ land cover classification scheme ware adopted and identified: agricultural land, built up area, vegetation and bare land. The result revealed that agricultural land coverage 66% in 2000, 64% in 2010 and 51% in 2020. The built up area coverage 29% in 2000, 27% in 2010 and 36% in 2020. The vegetation coverage increased 2% from 2000 to 2010, 5% from 2010 to 2020 and 8% from 2000 to 2020 and the bare land coverage 2% in 2000, 4% in 2010 and 5% in 2020. The factors that were responsible for horizontal expansion was increasing the demand for residential house of dwellers, growth and transformation plan (GTP), asphalt and gravel road construction, rural-urban migration, demographic dynamics, reclassification of the former rural settlement into new urban settlement, supporting housing policy and informal settlements. Generally urbanization was loss of agricultural land continuously. So, to prevent the loss of highly fertile and very productive agricultural land effective land use and land management strategies should be strongly encouraged. Furthermore, a sound policy at the local level is urgently needed. This study can be contributed to the government especially Adet town municipality and surroundings of Adet town, yilmana densa wereda, to ensure the developmental plans in certain areas other than highly fertile and very productive agriculture land and strengthen the zoning regulation and enact policies to reduce agriculture land losses and reclassification of the peripheral rural kebeles being as part of an administrative body to the town municipality. The finding of this study will also be significant in providing realistic information and initial input for urban planning experts, stakeholders, governmental and nongovernmental organizations and other researchers.
Assessment of Desert Locust Infestation by Using GIS and Remote Sensing Technology: A Case Study in Dire Dawa and the Northern Part of Somali Region, Ethiopia
(Addis Ababa University, 2022-06) Fentahun, Abebaw; Tibebu, Kassawmar (PhD)
Desert locust (Schistocerca gregaria, Forskal) is the most serious insect pest devastating and damaging agricultural products of cropland areas and pastureland during the invasion of locust. The main cause of desert locust outbreaks is the trigger of rainfall occurring and the growth of green vegetation expands the area and the population of locust density leads to an upsurge and possibly develop plagues. The aim of the study is to assess desert locust infestation using GIS and remote sensing technology. The open-source satellite data of EVI from MODIS with 250 m, sentinel-1 SAR data from Copernicus 10 m, DEM from SRTM 1 arc seconds, precipitation data from GPM 0.1 degree spatial resolution, and ground survey data were applied to analyze the effect of desert locust environmental variables of rainfall, vegetation, and digital elevation model (DEM), damaged vegetation assessment of desert locust and determine whether kriging interpolation correctly predict the unobserved area using the surveyed site. The methodology of the study was Preprocessing, reclassification, zonal attribute analysis, and geostatistical analysis of kriging, and (IDW) method of interpolation was performed. The distribution of locusts in September and October 2019 and September 2020 occurred in the Northern part of the study with low vegetation levels and low rainfall amount. However, in November 2019, October, and November 2020 desert locust infestations occupied and migrated to the southern part of the study area with high vegetation and rainfall. The lower mean pixel reflectance value of EVI data produced in September 2019 is 0.11 and a higher mean pixel value reflectance of 0.23 was produced in October 2020 damaged vegetation of desert locust infestation. Whereas the sentinel-1 SAR data value of lower mean pixel backscatter value of damaged vegetation (vertical-horizontal (VH -20.86 dB) and (vertical-vertical (VV -14.25 dB) produced October 2019) and higher mean pixel backscatter value (VH -17.78 dB and (VV -11.48 dB produced in September 2020). the kriging interpolation was applied to predict un-surveyed areas by the survey team using a surveyed site of spherical modeling. the regression value between measured and predicted of 2019 square r = 0.24 with p-value = 0.0003 and 2020 square r = 0.0084 and p-value = 0.26. The result indicates kriging interpolation need randomly distributed and accurately measured data.
Assessment of Groundwater Recharge Change Using WetSpass Model in the Birr Watershed, Abay Basin, Ethiopia.
(Addis Ababa University, 2023-06) Yiheys Degu; Andenet Ashagrie (PhD)
Understanding the long-term spatial extent of environmental and LULC changes in different time epochs helps to evaluate the impact of climate and LULC changes on water resources. Therefore, estimating the spatial and temporal extent of groundwater recharge in response to climate and LULC changes are crucial for the proper management of the water resources in the watershed. This study quantifies the effects of climate and LULC change on groundwater recharge for the Birr watershed from 1990-2020 periods using WetSpass model. The LULC maps of the study area were classified from multi-temporal Landsat imageries of Landsat 5(TM), Landsat 7(ETM+), and Landsat 8(OLI) using supervised maximum likelihood classification algorithm. The accuracy of classified images was checked by overall accuracy and kappa coefficient. In the study area, agriculture, built-up, and bare land increases through time while grassland, forest, wetland, and shrubland decreases during the last three decades due population growth and rapid expansion of farmland. The monthly reanalysis of climatological satellite products of precipitation, temperature, and windspeed maps was prepared from the decadal average of 1990-1999, 2000-2009, and 2010-2020 for the model simulation. The trend of the climate change in the watershed were analyzed and tested by Mann Kendall test R programming software. The temperature in the watershed has increasing trend over the last 30 year and increase by 0.033oc per year. Whereas, rainfall and wind speed have no significant trend in 95% confidence level. Moreover, a 12m resolution ALOSDEM was used to delineate the watershed and to develop slop and elevation input maps. The slope and elevation maps were finally resampled to 30m resolution. The study result shows that the annual groundwater recharge in the watershed decreases on average from 162.3mm to 128.6mm in from the first phase to the second phase and declines to 121.2mm in the third phase. it is important to take LULC conservation mechanisms and environmental rehabilitation measures in the study area. The study gives a piece of baseline information about impact of climate and LULC on the groundwater recharge of the study area for policymakers and the society of the watershed.
Assessment of Horizontal Positional Accuracy of Digital Orthophoto in the Town of Chiro, Ethiopia
(Addis Ababa University, 2021-09) Muhammed, Siraj; Tullu, Besha (PhD)
Positional accuracy is a matter of renewed concern and it deals with the accurateness of the location of map features, and measures how far a spatial feature on a map is from its true or reference location on the ground. A crucial component to examine an effective positional correctness of digital spatial data needs acquisition of better quality of independent ground reference data. This data makes spatial analysis less troublesome and enables better decision making. The objective of this thesis is to examine the horizontal positional accuracy of digital orthophoto. Accordingly, the study used in-situ Global Navigation Satellite System (GNSS) data to validate the accuracy of horizontal coordinates an Orthophoto located in Chiro town. GNSS data is observed using Leica GS 14 Differential Global Positioning System (GPS) instrument and post processed with different processing software’s like Leica Geo-Office (LGO) and online processing software’s using AUSPOS and OPUS with a tie to local and regional GNSS reference stations to obtain horizontal coordinates. In this paper the accuracy of horizontal coordinates of Digital Orthophoto was evaluated by comparing with the corresponding coordinates measured directly from in-situ GNSS data. As a result, the root mean square error between the orthophoto coordinates and in-situ GNSS coordinates of the nine check points in x and y-directions are 0.993 m and 1.462 m, 0.718 m and 1.712 m, 0.715 m and 1.709 m as compared to the GNSS data obtained from LGO, AUSPOS and OPUS processing respectively. In addition, the orthophoto horizontal accuracy was found to be 3.059 m, 3.213 m, and 3.206 m at 95 percent confidence level as compared to the GNSS data obtained from LGO, AUSPOS and OPUS processing respectively. Therefore, it can be concluded that, in all condition the accuracy of orthophoto doesn’t meet the national standard of error budget (30cm) for the purpose of Standard Mapping work use. Rather, it can use for Visualization and less accurate work use. In its present state, it can be used for a Master plan and General Economic development plan application.
Assessment of Land Use and Land Cover Change and its impact on LST Using Remotely Sensed Data: In and Around Gondar Town, Ethiopia
(Addis Ababa University, 2020-08) Frew, Fentahun; Ermias, Teferi (PhD)
Urban areas are the most dynamic regions in the world which always have a rapid change in both demographic and spatial dimensions. Urbanization is the main cause of global climate change and currently, it is a rising trend globally in general and in Ethiopia in particular. It has a significant influence on land use by substituting areas of natural resources and vegetation with impervious surfaces like built-up asphalt road and parking lots; which in turn increases the LST. The objective of the study was to assess urbanization/LULC and its impacts on LST in urban areas through taking in and around Gondar town. Supervised classification with maximum likelihood algorithm was used to assess the LULC changes and the split-window algorithm was used to extract LST from Landsat imageries which were acquired from 1988, 2002, and 2018 of the same seasons and MODIS LST was used to validate land surface temperature that was derived from Landsat thermal bands. Pearson correlation was used to analyze the relationship between LST and LULC indices (NDVI and NDBI). The results show that there is a significant change in LULC especially the built-up area of the study area which becomes more than triple over the study period from 2.85% - 12.82%. However, Vegetation areas are decreased from 18.78% to 11.4 % from 1988 to 2018. This implies that the areas covered by natural resources and vegetation are replaced with man-made features. Agricultural and bare land areas are also slightly decreased through the study period. This study shows that the LST of Gondar town ranges from 13.44 ℃ to 41.32 ℃ from 1988-2018. LST has a positive relationship with NDBI and a negative association between NDVI. Vegetated land and water bodies have low LST. However, most of the agricultural land, bare land, and central parts of Gondar town have high LST. There was a LULC change in Gondar town and it causes an increase in LST from 19882018. Therefore, the concerned body should have better environmental management strategies and thermal refreshing mechanisms.
Assessment of Potential Groundwater Zone Using Integrated GIS and Remote Sensing Techniques in Sekota Wereda, Northern Ethiopia.
(Addis Ababa University, 2018-09) Adem, Berihun; Ermias, Teferi (PhD)
Due to complex and erratic nature of groundwater occurrences in volcanic rock terrains, groundwater development in form of boreholes/wells without the necessary pre-drilling hydrogeological investigations usually results in failure. Therefore, there is the need for adequate characterization of aquifers and delineation of groundwater potential zones in such volcanic rock setting. This study employed the integration of multi-criteria decision analysis (MCDA), remote sensing (RS) and geographical information system (GIS) techniques to delineate groundwater potential zones in volcanic rock terrain of N-Ethiopia, Amhara Regional State, Wag Himra Zone of Sekota Wereda, and validation of the result with existing borehole/well yield data. The study approach involved integration of seven different thematic layers (lithology, land form, soil, drainage density, lineament density, land use and slope) based on weights assignment and normalization with respect to the relative contribution of the different themes to groundwater occurrence using Saaty’s analytic hierarchy approach. Following weigh normalization and ranking, the thematic maps were integrated using ArcGIS 10.1 software to generate the overall groundwater potential map for the study area. Finally, groundwater potential zones are classified into three categories namely low, moderate, and high zone. It is observed that 10.03% (167.5 km2) of the study area falls under ‘low’ groundwater potential zone. Approximately 1190.8 km2 area accounting for 71.4% of the study area falls under ‘moderate’ category and ‘high’ groundwater potential zone encompasses an area of 309.8 km2 accounting for 18.57 % of the total study area. Finally, the model generated groundwater potential zones are validated with potential yield data of various wells in the study area. The validation clearly highlights the efficiency of the integrated RS and GIS methods employed in this study as useful modern approach for proper groundwater resources evaluation; providing quick prospective guides for groundwater exploration and exploitation in such volcanic rock setting.
Assessment of Spatio-Temporal Pattern of Water Hyacinth And Its Dynamic with Seasonal Climate Variability and Impact on Evapotranspiration of Lake Tana Using Landsat And Sentinel-2
(Addis Ababa University, 2020-10) Takele, Abebe
Lake Tana is the largest Lake in Ethiopia which has been invaded by water hyacinth since 2011. However, there is lack of reliable estimates of annual and seasonal water hyacinth distribution and extent. Therefore, this study aims to assess the spatio-temporal pattern of water hyacinth and it’s dynamics with seasonal climate variability and impact on evapotranspiration using Landsat 7 ETM+, Landsat 8 OLI, Sentinel 2 and meteorological data. The area of water hyacinth and surface area of the Lake were mapped using supervised, unsupervised and manual digitizing image classification techniques. The trend of water hyacinth was determined using Mann-Kendall trend test and the impact of climate variability on water hyacinth spatial distribution was studied using Pearson correlation coefficient. The evapotranspiration and water losses were estimated from reference evapotranspiration computed using FAO-56 PenmanMonteith method and a crop coefficient value of 0.65 and 1.90. The results of the study revealed that there was a statistically significant increasing trend in annual spatial coverage of water hyacinth. The annual coverage areas of water hyacinth increased by 96% from 134ha in 2011 to 3019ha in 2019. However, the surface area of the Lake showed a decreasing trend. A total of 1834ha of the surface area of the Lake (0.6 % of the average surface area of the Lake) has lost over the last nine years. The annual maximum lake surface area was 306,399ha occurred in 2015 and the minimum was 302,952ha in 2019. The monthly and seasonal spatial-temporal dynamics of water hyacinth in Lake Tana exhibit a periodic cyclical pattern, reaching the highest peak in Bega followed by a decline to the least coverage level in Kiremt season. The highest growth areal extends of water hyacinth was 3830ha in 2018 November while, the minimum area was 396ha in 2017 July. The monthly surface area of the Lake was varied from 298,392ha in 2016 June to 317,257ha in 2018 July. The seasonal average surface area of the Lake was ranged between 301,817ha in Belg and 307,471ha in Kiremt season. The average daily evapotranspiration of water hyacinth in Lake Tana from 2016 September to 2018 December was 2.39 and 6.99 mm/day, and the average water loss in the Lake due the weed evapotranspiration was 35, 678 and 104,290 m3/day using Kc of 0.65 and 1.90 respectively. The total amount volume of water loss in Lake Tana from 2016 Sep to 2018 Dec was between 30,397,918 m and 88,855,452 m, 3 3 the average value represents 0.21 % of the volume of the Lake using a Kc value of 0.65 and 1.90. The Pearson correlation of monthly water hyacinth and rainfall was significant moderately negative (r= -0.63, p=0.03). The correlation of mean monthly temperature and wind speed with water hyacinth was negative (r = -0.34, p = 0.28) and (r = -0.59, p = 0.04) respectively. The seasonal correlation of the area of water hyacinth with rainfall and wind speed was insignificant moderately negative (r= -0.72, p=0.49) and (r= -0.62, p=0.57). Low insignificant negative correlation (r = -0.36, p = 0.76) with mean temperature was also attained in seasonal period. In general, the climate variability in Lake Tana Basin showed a less and insignificant contribution for distribution and spread of water hyacinth in study period.
Assessment of Urbanization and its Impact on Agricultural Land a case of Motta town, Ethiopia
(Addis Ababa University, 2024-06) Muhammed Belale; Andenet Ashagrie (PhD)
Urbanization poses significant challenges to the sustainability of agricultural land, which plays a crucial role in food security and local economies in rapidly urbanizing areas. The study assesses the impact of urbanization on agricultural land in Motta town using Geographic Information System (GIS) and remote sensing techniques. Land use and land cover (LULC) changes from 1992 to 2023 were analysed using Landsat satellite images from the United States Geological Survey (USGS). Both Supervised and unsupervised classification methods of classification were used to classify four land use classes namely built-up area, vegetation, bare land, and agricultural land. The study compared classification algorithms including Support Vector Machine (SVM), Maximum Likelihood Classification (MLC), and unsupervised classification based on their results and accuracy. Additionally, urbanization indices such as New Built-up Index (NBI), Urbanization intensity Index (UII), and Normalized Difference Built-up Index (NDBI) were employed to assess urbanization dynamics. Results indicate a consistent trend of agricultural land loss and built-up area increase. SVM classification shows built-up areas increasing from 323 hectares in 1992 to 607 hectares in 2023, with agricultural land decreasing from 944 hectares to 510 hectares. MLC classification similarly reveals an increase in built-up areas from 534 hectares to 757 hectares and a decrease in agricultural land from 791 hectares to 352 hectares by 2023. Unsupervised classification identifies an increase in built-up areas from 510 hectares to 910 hectares and a decrease in agricultural land from 695 hectares to 346 hectares over the studied period. Accuracy assessments confirm SVM as the most accurate method. The study concludes that urban expansion significantly diminishes agricultural land in Motta town and suggests implementing sustainable land use policies and employing satellite remote sensing for effective monitoring of urban sprawl to mitigate further agricultural land loss
Assessment of Vegetation Cover Change in Urban Green Spaces, a Case Study of Addis Ababa, Ethiopia
(Addis Ababa University, 2024-06) Melkamu Tarekegn; Andenet Ashagrie (PhD)
Urban green space (UGS) is crucial for maintaining ecological balance in rapidly urbanizing areas. This study aimed to estimate UGS and quantify oxygen production in Addis Ababa, Ethiopia, for the years 2017 and 2024 using Geographic Information System (GIS) and Remote Sensing (RS) technologies. Sentinel-2A satellite imagery was employed to analyze the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI), assessing changes in vegetation cover and built-up areas. UGS was categorized into dense vegetation, sparse vegetation, and shrub and grassland to estimate oxygen production. The results revealed a significant decline in green spaces and an expansion of built-up areas from 2017 to 2024, indicating rapid urbanization. In 2017, UGS covered 18,818.33 hectares, producing an estimated 33,872.994 tons of oxygen per year. Detailed oxygen production for 2017 included dense vegetation (2,663.39 tons/year), sparse vegetation (2,613.72 tons/year), and shrub and grassland (3,299.22 tons/year). By 2024, UGS reduced to 16,842.17 hectares, with an estimated oxygen production of 30,315.906 tons/year, including dense vegetation (2,862.129 tons/year), sparse vegetation (3,017.96 tons/year), and shrub and grassland (2,402.379 tons/year). Accuracy assessments using Google satellite imagery and ground-collected GPS data validated the classification results. These findings highlight the ecological impact of diminishing green spaces due to urbanization. This research underscores the urgent need for sustainable urban planning and the preservation of green spaces in Addis Ababa to mitigate adverse environmental effects and maintain ecological balance
Behavior of Piled Rafts on Multi-Layered Soil (A Case Study on Orda Project Of Addis Ababa)
(Addis Ababa University, 2020-06) Meron, Assefa; Henok, Fikre (PhD)
It is becoming abundant in Addis Ababa, to conservatively place high-rise buildings on deeper hard stratum through very long piles. However, the use of piled raft foundation seems to be more advantageous than the conventional pile foundation since both the raft and piles contribute to the resisting capacity of the system. In an attempt to investigate the extent of this principle, a case study was undertaken in this paper. The case under consideration, ORDA project of Addis Ababa, incorporates three blocks of different height, accessed as one building. The highest block of the structure rested on long piles to transfer the load to a basalt layer found at a great depth. In the study, the as-built conventional pile foundation scheme was analyzed and compared with that of a proposed piled raft foundation system. In doing so, a finite element analysis software, ABAQUS, was utilized to investigate the behavior of the foundation systems under study. The Effect of one block on the other as well as differential settlement due to varying loads of the blocks is considered in the analysis. The analysis result revealed that the proposed piled raft foundation was able to safely support the vertical load coming from the super structure by utilizing a shorter and much smaller number of piles than used in the as-built foundation system. It was possible to reduce the number of piles from 162 to 50 and the length of piles from 25.4m to 20.4m, with the adequate margin of safety. The enormous economic benefit of using piled rafts is also shown through direct comparison of expenses for the as-built and proposed foundations. A potential cost reduction of 75% was observed in the analysis.

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