Geodesy and Geomatics

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Instructors' Provision of Written Responses to Students' Business Letter Writing
(Addis Ababa University, 2003-07) Mengistu, Araya; Haile, Messele(PhD)
This study is conducted to prepare seismic microzonation map to central part of Addis Ababa City. The basic method used is the observation and analysis of microtremors. The first effort was made by Ayele (2001) based on 40 observation sites. Latter detailed study was initiated by dividing the city in to five parts namely the northeastern, northwestern, central, southeastern and southwestern parts of which the central part is the study area for this thesis. In this thesis seismicity and related hazard for Addis Ababa city and its locality, historic records, geologic conditions and effects on earthquake, and the theoretical background used in preparing microzonation maps are presented. The nature of microtremors, basic characteristics and their use in estimating site-effects is also discussed together with the method of measurement, equipments used and available tools to analyze collected data. The suitability of microtremor based site-effect study has been tested by comparison of results with solutions from one dimensional analytical model for selected sites.
Study on Local Steel Profiles in Steel Concrete Composite Bridges
(Addis Ababa University, 2009-08) Hailemariam, Dawit; Adamu, Asnake(PhD)
Building a functional transportation infrastructure is a high priority for a nation, particularly for developing country like ours. Currently, the Ethiopian government has given special attention for road construction sector and is to invest billions of dollars. Parallel to road construction, there is also a demand of construction of bridges as most of the existing ones are getting older as they are constructed, during colonization by Italians. Construction of such bridges naturally occupy longer construction time where the time required may be farther exacerbated due to shortage of budget beside having bad construction management practice which is observed in many construction undertakings. Associated with this, the normal day to day traffic flow is affected and causes discomforts to the road users. This problem is serious especially in towns where there is high traffic volume and provision of detours is not simple. Thus, as alternate, steel-concrete composite bridge which obviously shortens the construction time and alleviates the problems with other added advantages is thought in this study. Therefore, in this thesis attempt is being made to compare the usage of locally produced steel profile in steel-concrete composite bridges with the conventional reinforced concrete deck girder bridges cost wise, beside evaluating other merits of such application. In the thesis work, relevant literatures are reviewed, assessment of availability of local steel profiles for such application has been made to local private and governmental companies that are engaged in manufacturing, supplying and installing of such steel profiles for different engineering purposes. Kality Metal Products Factory, Mesfin Industrial Engineering PLC and Maru Metal Industry are among some whose local products are considered. Accordingly, it is observed that there is local capacity and experience of manufacturing I-section profiles by
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.
Software Development for Consolidation and Settlement Analysis
(Addis Ababa University, 2011-11) Ayenew, Yihune; Alemayehu, Teferra (Prof.)
Consolidation and settlement analysis is one of the main tasks of a geotechnical engineer. There are different methods of analyzing consolidation and settlement. In this study, software for the analysis of consolidation and settlement is developed. The developed software analyzes one dimensional consolidation for saturated and unsaturated soils. Consolidation analysis for saturated soils is done by the Fourier series solution and by finite difference solution of Terzaghi’s one dimensional consolidation equation for saturated soils. Consolidation analysis for unsaturated soils is done by finite difference method. The analysis is done for different loadings, scenarios, drainage conditions and soil conditions. The software analyzes immediate settlement, primary settlement and secondary settlement. Primary settlement calculation is done by compression index method, average modulus of compressibility method and coefficient of volume compressibility method. Secondary settlement calculation is done by constant modulus of compressibility method and variable modulus of compressibility method. The analysis is done for different loadings, foundation types, and locations of the foundation, drainage conditions and soil conditions. The result of consolidation analysis by Fourier series method and finite difference method give approximately similar result. For the consolidation analysis by finite difference method, the stability of the calculation is very sensitive to the beta value. The result may not be reliable for inappropriate beta values. The developed software can be used to analyze consolidation and settlement simply, quickly and accurately. Comparison of results obtained from different analysis methods of consolidation and settlement can be also made with the software. The developed software is also important to study the properties of the results for different values of input parameters.
Connection Study of Long Span Steel Truss Bridges
(Addis Ababa University, 2012-04) mebratie, Leule; Adamu, Asnake(PhD)
Safe and economic design of a structure is an indication of good computational process which has been followed in this work. This intensive computation of analysis and design of structural elements had great value in the transfer of loads. During the structural analysis of truss elements and design of the elements; joints between the truss chords play great role in transferring the force. The very custom of designing a connection element is standard detail information and even without an adaptation of the connection design and this situation is hardly very risky, for especially to Ethiopian case; because we even do not have a manual or a guide line for such a long span steel truss bridge connections. This problem calls for the study of long span steel truss bridge connections. Failure stresses of Connections of steel structural elements are verified and have got recommendations to handle or to minimize it. Thus, this research is intended to assess the reliable connection design process for all designers and for concerned governmental body who are responsible in code book or standard preparation.
Developing Correlation Between DCP And CBR For Locally Used Subgrade Materials
(Addis Ababa University, 2012-06) Yitagesu, Desalegn; Samuel, Tadesse (PhD)
California Bearing Ratio (CBR) is a commonly used indirect method to assess the sub grade soil strength in pavement design works. However, since CBR cannot be easily determined in the field, civil engineers always encounter difficulties in obtaining representative CBR values for design of pavement. Consequently, prediction of CBR va1ues from other direct soil field tests such as Dynamic Cone Penetrometer (DCP) is found to be a valuable alternative. The dynamic cone Penetrometer (DCP) is the most versatile rapid, in situ evaluation device currently available. Its correlations to CBR and its use in performance evaluation of pavement layers make it an attractive alternative to more expensive and time consuming procedures. Many useful correlations had been proposed by various researchers for soils of their locality in which the DCP penetration index was used to develop these correlations. A study was carried out to find the correlation between Cone Penetrometer (DCP) with CBR values that best suit the type of soils in Ethiopia. Accordingly, several laboratory tests and field tests on Jimma – Mizan, Contract 1: Jimma – Bonga road project from km 100+000 to km 105+000 has been conducted. From the tests, the Atterberg limits (PI, LL, PL), In situ density, classification (sieve analysis, hydrometer analysis), California bearing ratio, insitu Moisture Content, and Dynamic cone penetration results are acquired. Based on this laboratory and field test results analyses were carried out using SPSS software and the applicability of the existing correlations for Ethiopia soil on the aforesaid data was checked. From the analysis results, it is observed that the published correlations are not suitable to be used in Ethiopia. Consequently, a correlation had been proposed in the study to predict the CBR values of the sub grade soil from dynamic cone penetration test results. The relation obtained from statistical analysis relationship has an R 2 of 0.943 and is shown below. log (CBR) = 2.954 – 1.496log (DCPI) with R 2 = 0.943 The results of the statistical analysis show that good correlation does exist between the dynamic cone penetration indexes (DCPI) and unsoaked CBR values.
Evaluation Of EGM2008 by Means Of GPS/Levelling In Uganda
(Addis Ababa University, 2013-04) Dianah Rose Abeho; Roger Hipkin (PhD)
The global gravity model EGM2008 is evaluated in various regions of the country to assess if it is good enough for geodetic applications. The evaluation method involves comparison of geoid heights computed from the model with those computed at irregularly distributed GPS/levelling stations. For testing the model, a total of seven levelled benchmarks available in Uganda which belong to the New Khartoum datum are used. The spatial positions of these benchmarks were determined at mm accuracy, with respect to ITRF2008. The agreement between the EGM2008 geoid and the geoid undulation derived from GPS/levelling over the seven irregularly distributed benchmark points has a standard deviation of 0.255m, with a mean of -0.859m. The datum offset may be due the choice of Wo (potential of the geoid) and Uo (potential on the surface of the ellipsoid); using GRS80 for the gravitational reference system and WGS84 for the geometrical reference system; some possibly different tidal conventions; but, by using the same method of analysis for Ethiopia and Uganda, these absolute offset effects are eliminated when comparing the two so that the computed difference [0.118 m] in datum offset for the two states does tell us something about the differences in levelling datums. The standard deviation of 26 cm suggests that sparser, irregularly-distributed and inhomogenous gravity data for Uganda was used in the development of EGM2008 not ruling out errors in levelling since there is barely any documentation pertaining the accuracy of results obtained regarding the levelling network in Uganda.
Study of Second and third Order Ionospheric Effect on Global Positioning System (GPS) Signals Along The Equatorial Regions
(Addis Ababa University, 2013-04) Chanie, Asmamaw; Hunegnaw, Adisu (PhD)
Ionosphere is the major source of error for geodetic applications despite the fact that it’s possible to remove most of the effect using its dispersive nature. However, it’s only the first order of the ionospheric effect that can be removed using dual frequencies signal observations. The second and third order ionosphere effect cannot be removed though we can model their effects on geodetic applications such as their effects on Global Positioning System (GPS) signals. The study mainly focuses on the assessment of higher order (second and third) ionosphere effects on GPS for accurate positioning along the equatorial regions. Some stations at higher latitudes were also included in our GPS data processing for comparison purposes. GAMIT/GLOBK software was used to process the GPS data including a suite of other ancillary information. The time series of the residuals from the final GAMIT/GLOBK result were compared with the geomagnetic field effects and solar cycle (sunspot activities). High ionopheric effects on the GPS signals from stations along the equator were observed relative to stations at higher latitudes due to the fact that total electron content density is high along the equator. In addition to this, the contribution of Equatorial Electrojet (EEJ) to ionospheric disturbances is higher along the equator. Higher total electron content was also observed for the stations from the equatorial region in particular on years 2002 and 2012 as these are the years where solar activity were at maximum. Keywords: GPS, Higher order ionosphereic effects, Total electron contents density, Geomagnetic field
Modelling The Azimuthal Dependence of The Tropospheric Delay on GPS Using Gamit/GLOBK and the Updated Vienna Mapping Function
(Addis Ababa University, 2013-04) Makabayi Brian; Addisu Hunegnaw (PhD)
In order to improve the accuracy of point coordinates obtained by the Global Positioning System (GPS), it is important to model the atmospheric delay caused by the Troposphere (Neutral atmosphere). Until now the atmosphere has been considered to be horizontally layered and azimuthally symmetric. Although for most applications this assumption is appropriate, azimuthal asymmetry may introduce significant errors in geodetic measurements where high precision is required. Azimuthal variation of 20% is quite commonly observed in humid areas. The assumption of azimuthal symmetry may cause significant errors when the local troposphere has large lateral temperature, pressure or humidity gradient variations. Recent VLBI studies indicate that azimuth asymmetry effects at 150 Elevation typically produce a Root Mean Square (rms) variation of 7mm, but at times this effect can be as much as 5times. This research investigates the effect of azimuth asymmetry on Tropospheric delay modelling using GPS. The dependence of the Tropospheric Delay on azimuth of the satellites was modelled using GAMIT/GLOBK software and the application of the updated Vienna Mapping Function (VMF1) in Tropospheric Delay modelling was analyzed. A combination of different mapping functions (Vienna Mapping Function (VMF), Niell Mapping Function (NMF) and the Global Mapping Function (GMF)) with the corresponding a priori constraints (U-file (UFL) and Global Pressure Temperature (GPT 50) were used. The combination of VMF and UFL for a different number of gradients estimated per day was done for North America, Europe and Uganda GPS data. The combinations made were evaluated using the Repeatability graphs developed using GLOBK. The results were also presented using tables and line graphs. When the gradients are modelled, the accuracy of fixing the GPS points increases. The accuracy obtained is very low when the gradient is not estimated. The accuracy of the East and North offsets increased more than the up offset in this research since there was no serious storm surge. When the gradient estimated per day is two (2) the accuracy is sufficient for fixing the East and North offsets well as for the up offset, more gradients have to be estimated especially when there is a serious storm surge. VMF1 with GPT50 fix well the East and North offsets well as VMF1 and UFL fix the up offset better. When there is a serious storm surge, gradients more than three should be estimated per day to model the Tropospheric delay well. Different MF/APRIORI combinations should be varied with the number of gradients estimated per day. Meteorological Rinex Files (RNX) should be used as a priori zenith constraints in modelling the Tropospheric delay in the future.
Validation of the 2008 Earth Gravity Model Using Gps/Leveling Data – A Case Study Around Debre Birhan
(Addis Ababa University, 2013-06) Worku, Ermias; Besha, Tulu(PhD)
The accuracy of the 2008 Earth Gravity Model (EGM08) is evaluated using GPS/ Leveling data around Debre Birhan town. Now, the advents of satellites gravimetery and Global Positioning System have revolutionized the way Geopotential number is computed on the earth’s surface. The Space Domain Spherical Harmonic Analysis of the EGM08 Stokes’ dimensionless coefficients Cn,m and Sn,m provides Geopotential height at GPS observation points. This study compared the EGM08 derived orthometric height, normal height, geoid and height anomaly with GPS/Leveling data. Three first order Blue Nile leveling benchmarks available around Deber Birhan town with a tie to the port of Alexandria mean sea level tide gauge datum were used for evaluating the quality of EGM08. A total length of 1200 m first order geodetic leveling work was done to shift all the three old Blue Nile leveling benchmarks to new locations that have good GPS satellite visibility. The spatial GPS coordinates of these benchmarks through which the Geopotential heights are computed were determined within few millimeter accuracy using GAMIT/GLOBK software. The accuracy of the EGM08 derived Geopotential heights are in general good to few centimeters when compared to GPS/Leveling data. The agreement between the orthometric height derived from EGM08 and level heights has a standard deviation of 2.41cm with a mean of -3.14cm. This error is reduced to 1.09cm when the prey assumption for mean gravity is constrained by surface gravity observation. Besides, the comparisons of the gravimetric geoid and gravimetric height anomaly (zeta) with the geoid undulation derived from GPS/Leveling, have a standard deviation of 2.24cm & 2.26cm, respectively. In general, the comparison of orthometric height with level height gave the best result with datum offset of -3.73 cm between the gravimetric geoid defined by Wo=Uo and leveling datum. The datum offset may be attributed to the choice of the Wo value and real displacement between the mean sea level and the geoid. Key words: Geopotential height, leveling height, EGM08, GPS coordinates.
Modern Geodetic 2d and 3d Cadastral Mapping-A Case Study of Arat Kilo Campus
(Addis Ababa University, 2013-06) Firdisa, Diriba; Besha, Tulu
This study used satellite Global Positioning System and optical ground-based total station positioning system in an integrated approach to determine a modern geodetic measurement based 2D and 3D cadastral system for Addis Ababa University Science Faculty usually called Arat kilo campus. This provides a parcel-based land and cadastral property spatial and non-spatial registration with a tie to an absolute and global geodetic positioning reference system. Previously, cadastral land property registration was determined traditionally on a paper map using simple architectural drawing that describes the relative location of a particular land parcel and properties on it with respect to a well known locality names (e.g., street name, building name, etc) – the old cadastral system has no spatial component. Now, with the advent of GPS positioning system and optical total station this conventional cadastral system which has been based on non-spatial parcel based registration becomes obsolesce. The modern cadastral registration system has to tie the non-spatial administrative cadastral component to its corresponding spatial component. The new approach uses GPS receiver and optical total station to map the 2D and 3D representations of the cadastral properties. GAMIT/GLOBK was used to eliminate the errors from GPS observations to establish first order cadastral surveying fundamental control points accurate to centimeter level. This provides a unique opportunity to establish a well distributed high accuracy (~ 5cm) second order cadastral surveying control benchmarks using optical total station measurements with a tie to the first order GPS-based survey control points so as to carry out high resolution 2D and 3D cadastral mapping. The combined GPS and Total station surveying techniques have registered the 2D and 3D spatial information of about five cadastral properties occupying an area of 34376 square meters. 26% of the 2D cadastral registration corresponds to buildings, while 1%, 1%, 2%, 1% corresponds to Green area, playground, walkway and asphalt road respectively.
Comparison of Ppp And Double Differencing Solutions Case Study Campaign Gps Stations in Tanzania
(Addis Ababa University, 2013-07) Vincent, Leonard; Hunegnaw, Addisu(PhD)
Satellite Positioning systems are world-wide precise positioning systems and very useful for geodetic surveys, crustal deformation studies, station coordinates, absolute and relative station velocities. Two techniques for GPS data processing to obtain station position coordinates exist. The two methods are Differencing of observations, and Zero differencing techniques, known as Precise Point Positioning. The main aim of this study was to assess the accuracy of PPP Solution, using the already known accurate Double differencing solution. The data used in this study are three episodes’ campaign GPS stations in Tanzania established in 2006, 2008 and 2010. The data sets are available in RINEX format from the UNAVCO website. Double differencing was done using GAMIT_GLOBK software, in this case, the campaign data were combined in a solution experiment with reference GPS data for IGS stations in Africa, active from 2006-2010. The PPP solution was obtained from APPS (online-GIPSY/OASIS). Other available online PPP solution services were also used for comparison purposes. The results from APPS PPP solution were compared with GAMIT/GLOB DGPS solution in order to assess the accuracy of PPP. From 330, 24hours epochs of observations the results show that the range of the difference between GAMIT/GLOBK and APPS PPP solution is -3.7 to 5.6cm in X component, -3.8 to 5.0cm in Y component and -1cm to 3.4cm in the Z component. The residuals of coordinates (δX, δY and δZ) from the two solutions have mean value of 5.9mm in X component, 1.2mm in Y component and 0.4mm in Z component. Also the standard deviations in δX, δY and δZ are 11mm, 10mm and 4mm respectively. From the results analysis it has been shown that in most cases, for the data set used, PPP solution is very close to DGPS solution. Key words: Precise Point Positioning (PPP) Differential GPS (DGPS)
Deformation Analysis at the Northeastern Part of Semera Town Centeral Afar Using Insar and Gps
(Addis Ababa University, 2013-07) Temtime, Tesfaye; Hipkin, Roger(PhD)
This study is conducted to analyze the deformation pattern at a locality in the central part of Afar, northeast of Semera town, within the triple junction that is formed by the Arabian, Nubian and Somalian diverging plates. The study area is bordered by Manda Harraro rift in the northwest and Tendaho rift in the south. The region is one of the tectonically active areas in the world, where the episode of plate movement resulted in seafloor spreading that causes the earth‟s surface to deform in the form of surface cracking, sliding and faulting. Presently this dynamic process of earth‟s deformation in space and time can be accurately detected by satellite space geodetic observations. This study used Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) to study earth surface deformation. InSAR data from Envisat, image mode, with track 028 ascending and track 278 descending is used to detect surface deformation over the study area. To constrain the InSAR observations, continuously recorded GPS data obtained from DASM (2007-2012) and DASA (2008-2009) are used to investigate possible surface deformation changes in the area. The three dimensional position coordinates acquired from the DASM and DASA GPS stations over their period of observations have suggested a ground surface deformation rate of 48.5+0.2mm/yr North, 39.5+0.2mm/yr East and -9.5+0.7mm/yr Up; and 27.8+0.4mm/yr North, 43.9+0.5mm/yr East and -21.8+1.4mm/yr Up for DASM and DASA GPS stations, respectively in an absolute sense. The Up component of DASM shows two characteristics, 2.8 mm/yr up to doy 150, 2008 and -25mm/yr afterwards. The DASA shows also -10mm/yr up to doy 147, 2008 and -29mm/yr afterwards. The InSAR time-series shows -44mm/yr Line of Sight (LOS) rate in both track. The correlation between the DASM GPS and track 028 is 0.75 and it has a correlation of 0.79 with track 278. Generally, the result from this investigation suggested that there is an active subsidence in the area which needs further attention. Keywords: Deformation, InSAR, GPS, LOS
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
Ground Response Analysis of Selected Sites in Hawassa Area
(Addis Ababa University, 2017-11) Besrat, Eshetu; Alemayehu, Teferra (Prof.)
Hawassa, a lakeside city in southern Ethiopia found at the heart of the East African Rift system, has been frequented with a series of minor to strong earthquakes reaching up to a magnitude of 7. A recent minor earthquake caused structural distresses in the city that tempts one to hypothesize that this may be principally attributed to the young lacustrine deposit typical of the city. Primary data from refraction and resistivity tests and secondary data from available geotechnical reports were collected from different locations of the city so as to model respective soil profiles. Due to lack of measured strong ground motion records in the area, input motions were selected from PEER database using relevant filtering criteria and scaled according to the local seismic hazard. The selected ground motions are used in a one-dimensional ground response analysis software, DEEPSOIL, and responses at the surface and at various depths are obtained. A typical geotechnical profile across the city consists of a thick silty sand soil with a thin horizon of welded-tuff at a shallow depth. The results obtained from the study show that ground motions are greatly influenced by local site soils across the selected locations, with amplifications much exceeding the prediction of design spectra specified by current codes. This led to the proposal of a design spectrum that fitted the analysis outputs from 56 cases.
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.
Remote Sensing Based Microclimate Change Study in Clustered Industrial Areas of Addis Ababa City.
(Addis Ababa University, 2018-10) Kemal, Husen; Degefie, Tibebe (PhD)
Microclimatic warming is the major effect of industrial expansion in urban areas like Addis Ababa. Monitoring of microclimatic warming at local scale is very required to take proper decision. However, microclimatic warming with respect to recent industrial development in Addis Ababa city is not yet investigated. Thus, in this study multi temporal Landsat satellite images are used to evaluate the spatio-temporal trend of microclimate warming in urban areas of Addis Ababa. Thermal infrared and near infrared portion of the electromagnetic spectrum of Landsat satellite imageries are employed to compute land surface temperature which is used as a warming indicator of microclimatic warming. Landsat imageries which were taken up during 1985 G.C to 2018 G.C are considered in this study. Apart from satellite imageries, temperature data from ground station is obtained from National Meteorological Agency of Ethiopia. This data is used to evaluate against satellite derived land surface temperature. Result from this study shows that in general temperature in Addis Ababa has been increased in the last 33 years and this particularly exhibited in clustered industrial zones of the city whereby the rate of temperature increment is higher compared to the whole city. This clearly indicates that the association of industries expansion and temperature rise is directly associated. Based on this information, solutions are suggested to manage the effect of industrial expansion on local microclimatic warming.
Horizontal Accuracy Assessment of Digital Aerial Photograph in Urban Cadaster: The Case of Wereda 10, Gulelie Sub-City, Addis Ababa
(Addis Ababa University, 2018-10) Azeneg, Eneyew; Andinet, Ashagrie (Mr.)
Positional accuracy deals with the accuracy 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. This research focused on the following problems: Coordinate shifting, area variation and shape difference between the ground measurement, line maps and digital aerial image. The main objective of this study is to assess the horizontal position accuracy of aerial photogrammetric image generated coordinates of Wereda 10, Gulelie sub city. There are three basic data sources used to assess horizontal accuracy assessment: Such as Geo referenced digital aerial photograph, digital line map and GPS data. This research contains the following steps: First step created twenty sample GCP points by using static GPS. The seconded step is process sample GCP points by using Leica Geo office combined software. While, the third step is measured hundred parcel corners points by using RTK GPS as a reference used the established GCP points. In addition, the fourth step is digitized parcel corner points and polygons from aerial photograph and digital line map. Finally, assessed horizontal accuracy, standard deviation, means value, minimum and maximum values. The paper describes the visualization possibility of estimated results of horizontal positional accuracy of digital aerial photographs and established cheek points and area, side length and coordinates comparison for digital aerial image and digital line map based on RTK GPS. The root mean square error results of twenty check points and digital aerial photograph the easting and northing component is 18.1cm and 18.8cm, respectively. The RTK GPS and aerial image comparison coordinates results show that the root mean square error of easting and northing component is 37.6cm and 38cm respectively. The RTK GPS and digital line map coordinates comparison results show that the root mean square error of easting and northing component is 39.2cm and 39.8cm respectively. The root mean square error is 5.828 m2 and 5.852 m2 in aerial photograph and digital line map respectively. The root mean square error is 38.1cm and 40 cm in aerial photograph and digital line map side lengths respectively. Therefore, these variations come from different factors: Such as shadows, topographic factors, vegetation covers and there are some limitations to these techniques as it solely on visual interpretation.
Urban Landscape Dynamics and the Implication on Surface Urban Heat Island: The Case of Hawassa Town and Surrounding Area, Ethiopia
(Addis Ababa University, 2018-11) Mohammed, Habtamu; Berhan, Gessesse (PhD)
The Hawassa Town was experienced a rapid urban expansion over the past two decades because of accelerated economic growth and increase in population which resulted in unplanned urbanization. Due to this, land use land cover change has been formed and will result environmental problems and challenges. To notice the above-mentioned problems, exploring the land use land cover dynamics which will finally resulted in the emergency of Urban Heat Island (UHI) will be assessed that will value` both the communities and local government in the cities. This research work was conducted on the relationship between land use transformation and its implication on land surface temperature change at the heart of rift valley, Hawassa Town, Ethiopia. Remote sensing, GIS techniques and statistical methods were mainly employed for data analysis. A series of Landsat data was used to assess and analyze urban landscape dynamics and land surface temperature. It does so by generating land use land cover maps derived from Landsat 5 TM for 1986, 1998 and 2010, and Landsat 8 OLI for 2017, using supervise classification techniques. Spatial pattern analysis of LST was performed using thermal band of landsat images. Cross tabulation methods, regression analysis and hotspot analysis was employed to study to urban landscape dynamics and land surface temperature. Based on the analysis done, it was obtained that the areal extant of urban (built-up) area has increased considerably by 121.68%.The increasing difference of Surface Heat Intensity (SHIn) between urban area and non-urban area was distinguished. For instance, non-urban area was cooler than the urban area except the agriculture sector. As per calculation performed, the difference of the mean of hotspot and mean of cold spot areas ranged from 8.8 °C to 14.37 °C. Therefore, increasing surface heat intensity was observed between 1986 and 2017. The surface temperature was found to be greater for agriculture and urban (built-up) land use land cover types. Finally, it has been concluded that, with rapid urbanization, surface thermal intensity increased but relationships with vegetation, water bodies and swampy area suggest that optional for mitigating urban warming in tropical climate may be available. The use of hotspot analysis and the investigations of the Urban Heat Island (UHI) will fill the research gaps for the rest of Ethiopian city for studies of urban thermal variations.
Planimetric Accuracy Assessment of Digital Spatial Data for Large Scale Planimetric Mapping: The Case Study on Dire Dawa City, Ethiopia
(Addis Ababa University, 2018-11) Ephrem, Mulugeta; Andinet, Ashagrie (Mr.)
This study assesses the planimetric (x, y) accuracy of digital spatial data used for mapping large scale planimetric maps in Dire Dawa city. These digital spatial data are Orthophoto and its line map (parcel and road center line) and Worldview-1 panchromatic satellite image. RTK GPS measurement technique was used as an independent source and point wise method were used to assess the planimetric accuracy the digital spatial data set. Due to unavailability of local CORS station which used as a reference during RTK GPS measurement second order GCPs which was established by E.G.I.A (Ethiopian Geospatial Information Agency) was used as a base station. But before conducting RTK GPS survey a 12 hour static GPS survey were conducted on selected two second order and one first order GCP established by E.G.I.A and the GPS data are processed with a tie to IGS CORS station found in Addis Abeba and two free online GPS data processing service provider that are AUSPOS and OPUS. For accuracy comparison OPUS processed coordinates result were taken. However, the positional accuracy of selected GCP has mean error of -0.77m and 2.4m on x and y direction respectively. Therefore due to discrepancy of coordinate obtained from E.G.I.A and processed coordinate planimetric accuracy of orthophoto was assessed twice for selected 20 points with reference to RTK survey coordinates computed from E.G.I.A GCP and computed coordinate from IGS station. The planimetric accuracy of orthophoto relative to GCP established by E.G.I.A has good accuracy than coordinate computed from current derived coordinate from IGS station. Based on this relative to E.G.I.A GCP the planimetric accuracy orthophoto for the selected 20 points has RMSE of 0.138m and 0.15m on X and Y direction respectively and with respect to computed coordinate the planimetric accuracy of orthophoto has RMSE of 0.67m and 2.498 on X and Y direction respectively. Thus to increase the significance and applicability of this study finding the remaining line and polygon feature of orthophoto and its line map and satellite image derived coordinate compared with RTK survey coordinate correction computed from reference E.G.I.A second order GCP. Therefore the planimetric accuracy of orthophoto for the selected parcels, line and points are computed separately relative to RTK survey results thus the RMSE of these feature lie between 0.138m-0.22m and 0.12m – 0.24m on x and y direction respectively and 95% confidence level lie between 0.37cm and 0.55 cm and the planimetric accuracy of digital line map (parcel) RMSE are 0.173m and 0.196m on x and y direction respectively and 0.45m with 95% confidence level. The digital line map (road center line) also assessed its planimetric accuracy relative to coordinates obtained from RTK GPS survey coordinates and has RMSE of 0.148m and 0.191m on x and y direction respectively and 0.41m at 95% confidence level. Similarly the planimetric accuracy of worldview-1 satellite image assessed on similar sample parcel and line (flood protection fence) feature with that of orthophoto. Thus planimetric coordinates extracted from selected sample feature from satellite image are compared with Coordinates obtained from RTK GPS survey on similar feature. Based on this parcel feature has an RMSE of 1.73m and 2.06m on x and y respectively and 4.67m at 95% confidence level. The planimetric accuracy of line feature (flood protection fence) has RMSE of 1.89m and 2.25m on x and y direction respectively and 5.09m at 95% confidence level. The planimetric accuracy assessment result obtained from orthophoto and its digital line map based national accuracy standard for legal cadastre 03/2015 and ASPRS international digital spatial data set accuracy standard are applicable for large scale urban cadastral map and . However the planimetric accuracy of worldview-1 satellite image is not applicable for large scale cadastral map production.

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