Geodetic Science

The use of GPS for the estimation of orthometric heights in a given region, with the help of existing levelling data requires the determination of a local geoid and the bias between the local levelling and the one implicitly defined when the geoid is calculated which is generally based on the gravity anomalies data. The heights of new data can

The very accurate measuring of three-dimensional models of complex surfaces and objects in general (and their creation, as well), are subjects of the three-dimensional Metrology (3D-Metrology). In order 3D-Metrology to connect effectively the physical world with the virtual world (and vice versa), there is a need of measurements, methodologies of measurements and calculations. In this area, the contribution of the science of Geodesy, a science of spatial measurements, is of paramount importance. In this paper, a review and analysis of both, methods (or principles) and measuring instruments are carried out. These methods and instruments, although they belong to Geodesy (specifically in a branch of it, also known as: Geodetic Metrology, Technical Geodesy or Industrial Geodesy), they also form fundamental milestones of 3D-Metrology.

Publisher / Botues:
Geo-SEE Institute, Skopje, Macedonia      www.geo-see.org

Editor-in-chief / Kryeredaktor:
Dr. Bashkim IDRIZI, State University of Tetova, Skopje, Macedonia

Associate editor / Zëvendës i Kryeredaktorit:
Dr. Afërdita Laska-Merkoci, University of Tirana, Institute of energy water and environment, Tirana, Albania

Technical editor / Redaktor teknik:
Dr. Subija IZEIROSKI, Geo-SEE Institute, Struga, Macedonia

Editorial board / Këshilli redaktues:
Dr. Temenoujka BANDROVA , University of Architecture, Civil Engineering and Geodesy, Sofia, Bulgaria
Dr. Rahmi Celik, Istanbul Technical University, Istanbul, Turkey
Dr. Joep CROMPVOETS, Public Governance Institute, KU Leuven, Leuven, Belgium
Dr. Mahesh GAUR, Central Arid Zone Research Institute, India
Dr. Ferim GASHI, University of Prishtina, Prishtina, Kosova
Dr. Ismail KABASHI, Angst, Vienna, Austria
Dr. Milan KONECNY, Geography department, Masaryk University, Brno, Czech Republic
Dr. Elena KOTEVSKA, Faculty of Technical Sciences, University "St. Kliment Ohridski", Bitola, Macedonia.
Dr. Pal NIKOLLI, University of Tirana, Tirana, Albania
Dr. Lyubka PASHOVA, National Institute of Geodesy, Geophysics and Geography, BAS, Sofia, Bulgaria
Dr. Gabor REMETEY-FULOPP, Hungarian Association for Geo-Information, Budapest, Hungary
Dr. Guenther RETSCHER, Department of geodesy and geoinformation, Vienna University of Technology, Vienna, Austria
Dr. Vladimir S. TIKUNOV, Faculty of Geography, M.V. Lomonosov Moscow State University, Moscow, Rusia
Dr. E. Lynn USERY, Center of Excellence for Geospatial Information Science, U.S. Geological Survey, Rolla, USA

http://mmm-gi.blogspot.com/p/number4year2015.html

Despite the harmful effects of invasive species, the mechanisms behind the invasion and dynamics of invasive alien species are poorly understood in Ethiopia. Geographical Information Systems are emerging as valuable and cost-effective tools for understanding invasion dynamics and prioritizing management efforts these days. Moreover, remote sensing is the only practical method to acquire spatially and temporal detailed data over a large area. Because images can be acquired multiple times and provides a way to directly assess changes over time. This study was done in Amibara woreda in the Afar National Regional State. The objectives were: to evaluate the land-use/land cover change in the last two decades, examine the spatial distribution of                P. juliflora in the study area, assess the temporal dynamics of P. juliflora invasion and to determine the rate of invasion, and identify the land-use/land cover types which are affected by P. juliflora and explore the possible causes. Post classification comparison change detection scheme was employed to discriminate spatial and temporal invasion of P. juliflora between 1986 and 2007. The invaded land which was 769 ha in 1986 changed to 3,849 ha by 2001 and highly increased to 11,579 ha by 2007 year. During this period, almost all the land-use/land cover has been invaded by P. juliflora. Shrub land was the most affected land-use/land cover having 2,742 ha area invaded by P. juliflora. Between 2001-2007, the overall change of all other land use/land cover to P. juliflora invaded land have showed at least two fold increase than during 1986-2001 period except the cultivated land that was reduced by half in percent invasion. Hence, the rate of change from other land-use/land cover to invaded land has shown an increasing pattern in 0.06% area per year in 1986-2001 to 0.37% per year of the study area in 2001-2007. If this situation continues with out proper management it will not take longer to see these areas reaching at climax invasion, where it reaches impossible to think of management. The consequence will not only be of the Woreda level or Regional level but also at the National level. Hence, a GIS Model and Remote Sensing application in order to show further risk zone and its invasion driving forces should be carried out in the area. This helps to plan an immediate control and management options and strong policy to organize different stakeholders starting from lower level to regional level on the invasive species P. juliflora.
Key words: ASTER, Landsat, invasive species, invaded land, livelihood, land-use/land cover

The use of GPS for the estimation of orthometric heights in a given region, with the help of existing levelling data requires the determination of a local geoid and the bias between the local levelling and the one implicitly defined when the geoid is calculated which is generally based on the gravity anomalies data. The heights of new data can be collected swiftly without using the orthometric heights from levelling; it is what one calls commonly levelling by GPS. In this framework, the Least Squares Collocation method (LSC) has been used to evaluate the quality of the available GPS-Levelling data, to determine a gravimetric geoid in the North region of Algeria and to estimate the constant datum bias. The data used in the setting of this study are: The geopotential model EGM96, a total number of 2534 gravity anomalies, as well as 43 GPS points connected to the geodetic network levelling present on the whole North part of Algerian.

Land Surveying techniques are rapidly changed from conventional methods towards modern technological methods during the past two decades. The invasions of Global Navigation Satellite Systems (GNSS) in surveying applications have made it more efficient and cost effective. The uses of GNSS have substantially increased the requirement of a high resolution geoid model in converting the ellipsoidal height to orthometric height which has a physical meaning, as GNSS systems provides height and location information with respect to World Geodetic System 1984 (WGS84). Conventional geoid determination techniques require dense and homogeneous gravity measurements. In most of the regions gravity measurements are confined to more accessible low elevation terrain and also to establish such dense gravity network requires much cost and effort which is a highly concerned matter for most of the developing countries. Hence the observed gravity anomalies do not represent the true anomalies over the topography. This study concerns geoid modeling using a high resolution geopotential model and terrain data termed combined geoid determination through Residual Terrain Model (RTM) reduction method, where no dense land gravity data is required.
This method was applied for Ratnapura district in Sri Lanka which covers an area of 3,275 km2 and located to the southwest and south of the Central Highlands and lies between 6° 15' N~ 6°55'N latitude and 80° 10'.E~ 80°57'E longitude. In estimation of the local geoid model, the high resolution global geopotential model Earth Gravitational Model (EGM2008) is used as the reference field. It is capable of representing long to medium wavelength gravity field whilst truncation at its maximum degree and order leads to omission error where short wavelength features are not represented. Global Positioning System (GPS) leveling data is used to constrain long wavelength geoid errors. RTM reduction method accounts for the omission errors. Shuttle Radar Topography Mission (SRTM3) data and Digital Terrain Model (DTM2006.0) spherical harmonic model elevation data are used to calculate the RTM effect. The topographic corrections were applied through rectangular prism forward modeling methods and Bruns formula. Hence the correction was applied to the reference global geoid model for better vertical accuracies in deriving orthometric heights. A polynomial was fitted to the final correction model and estimated coefficients are presented in results with 95% confidence. Accuracy assessment of the estimated model through cross validation and real time filed data is yet to be done.

One of the major challenges of satellite altimetry (SA) is to produce accurate sea surface heights data up to the shoreline, especially in geomorphologically complex sea areas. New advanced re-tracking methods are expected to deliver better results. This study examines the achievable accuracy of Sentinel-3A (S3A) and Jason-3 (JA3) standard retrackers (Ocean and MLE4) with that of improved retrackers adapted for coastal and sea ice conditions (ALES+ SAR for S3A and ALES+ for JA3). The validation of SA data was performed by the integration of tide gauges, hydrodynamic model and high-resolution geoid model. The geoid being a key component that links the vertical reference datum of the SA with other utilized sources. The method is tested in the eastern section of Baltic Sea. The results indicate that on average reliable sea surface height (SSH) data can be obtained 2–3 km from the coastline for S3A (for both Ocean and ALES+SAR) whilst an average distance of 7–10 km for JA3 (MLE4 and ALE...

This paper is concerned with the study of new turbulent method technique for the determining of vertical refraction when total stations are used. Required measurement accuracy of vertical refraction by conventional methods is extremely di cult due to rapid random changes in the angle of refraction. Geodetic observations are recommended to performing only during periods of indi erent temperature strati cation, while the refraction is close to zero and practically unvaried. However, this period is extremely short and its boundaries are not de ned, so the ine ciency of all known methods for determining refraction must be attention. The complete liberation of geodetic observations from the in uence of turbulent and uctuation processes in the atmosphere is possible only by directly measuring the angle of refraction at the time of observation. The creation of electronic total stations with automatic guidance to the target allows to successfully solving the problem of determining refractio...

This paper is concerned with the study of new turbulent method technique for the determining of vertical refraction when total stations are used. Required measurement accuracy of vertical refraction by conventional methods is extremely difficult due to rapid random changes in the angle of refraction. Geodetic observations are recommended to performing only during periods of indifferent temperature stratification, while the refraction is close to zero and practically unvaried. However, this period is extremely short and its boundaries are not defined, so the inefficiency of all known methods for determining refraction must be attention. The complete liberation of geodetic observations from the influence of turbulent and fluctuation processes in the atmosphere is possible only by directly measuring the angle of refraction at the time of observation. The creation of electronic total stations with automatic guidance to the target allows to successfully solving the problem of determining...

The performance of GOCE-based geopotential models is assessed for the estimation of offsets for three regional vertical datums in Canada with respect to a global equipotential surface using the GNSS benchmarks from the first-order vertical control network. Factors that affect the computed value of the local vertical datum offset include the GOCE commission and omission errors, measurement errors, the configuration of the network of GNSS/levelling benchmarks, and systematic levelling errors and distortions propagated through the vertical control network. Among these various factors, the effect of the GOCE omission error on the datum offsets is investigated by extending the models with the high resolution gravity field model EGM2008 and by means of Canada’s official high resolution geoid model CGG2010. The effect of the GOCE commission error in combination with errors from the GNSS/levelling data is also examined, in addition to the effect of systematic levelling errors. In Canada, th...

For many developing countries such as Uganda, precise gravimetric geoid determination is hindered by the low quantity and quality of the terrestrial gravity data. With only one gravity data point per 65 km2, gravimetric geoid determination in Uganda appears an impossible task. However, recent advances in geoid modelling techniques coupled with the gravity-field anomalies from the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission have opened new avenues for geoid determination especially for areas with sparse terrestrial gravity. The present study therefore investigates the computation of a gravimetric geoid model overUganda (UGG2014) using the Least Squares Modification of Stokes formula with additive corrections. UGG2014 was derived from sparse terrestrial gravity data from the International Gravimetric Bureau, the 3 arc second SRTM ver4.1 Digital Elevation Model from CGIAR-CSI and the GOCE-only global geopotential model GO_CONS_GCF_2_TIM_R5. To com...

This paper evaluates a number of latest releases of GOCE/GRACE global geopotential models (GGMs) using the GPS-levelling geometric geoid heights, terrestrial gravity data and existing local gravimetric models. We investigate each global model at every 5 degree of spherical harmonics. Our analysis shows that the satellite-only models derived by space-wise and time-wise approaches (SPW_R1, SPW_R2 TIM_R1 and TIM_R2), GOCO01S together with EGM08 (combined model) are very distinct and consistent to the local data, which guarantees one of them to be selected as the best of candidate models and then to be utilized in our further geoid studies. One of Satellite-only models will be employed for acquiring the long wavelength geoid component which is one of major steps in the geoid determination. EGM08 will be used to compensate and restore the missing gravity data points in the un-surveyed parts within the target area. We expect further improvements in geoid studies in Sudan due to the improved medium wavelength part of the gravity field from GOCE mission.

We analyzed the noise characteristics of 112 continuously operating GPS stations in eastern North America using the Spectral Analysis and the Maximum Likelihood Estimation (MLE) methods. Results of both methods show that the combination ofwhite plus flicker noise is the best model for describing the stochastic part of the position time series. We explored this further using the MLE in the time domain by testing noise models of (a) powerlaw, (b)white, (c)white plus flicker, (d)white plus randomwalk, and (e) white plus flicker plus random-walk. The results show that amplitudes of all noise models are smallest in the north direction and largest in the vertical direction. While amplitudes of white noise model in (c–e) are almost equal across the study area, they are prevailed by the flicker and Random-walk noise for all directions. Assuming flicker noise model increases uncertainties of the estimated velocities by a factor of 5–38 compared to the white noise model.

The existing Canadian Geodetic Vertical Datum of 1928 (CGVD28) does not meet the needs of the modern user in terms of accuracy and accessibility. As a result, Canada plans to implement a geoid-based and global navigation satellite system (GNSS)-accessible vertical datum by 2013. One of the primary concerns in realizing this new vertical datum is to determine a W0 value that will represent the potential of the zero height surface. The objective of this study is to evaluate W0 by averaging the potential of points on the mean sea water surface utilizing tide gauge recordings and gravity field and steady-state ocean circulation explorer (GOCE)-based global geopotential models. In order to assess the performance of the GOCE-based models for the computation of W0, the models are extended with the high resolution gravitational model EGM2008. Regional gravimetric geoid models are also used for the estimation of W0. Additionally, local sea surface topography models are utilized in order to v...

https://www.ijert.org/geochemical-characterization-and-provenance-study-of-ilmenites-from-fluvial-sediments-of-river-cauvery-in-parts-of-tamil-nadu-southern-india

https://www.ijert.org/research/geochemical-characterization-and-provenance-study-of-ilmenites-from-fluvial-sediments-of-river-cauvery-in-parts-of-tamil-nadu-southern-india-IJERTV9IS010035.pdf

The Cauvery river is the third longest flowing river in South India. This river flows through three Southern Indian states (Karnataka, Tamil-Nadu, and Puducherry). The river Cauvery takes its birth at a place called Talacauvery in the state of Karnataka, and after a long journey of 800Kms from the Western-Ghats finally forms a delta and joins the Bay of Bengal in the east. This river traverses high grade metamorphic rocks. Ilmenites are good indicators of provenance and several researchers throughout the globe have contributed on this aspect. The present study is focused on chemical characterization of the detrital ilmenite from the fluvial sediments of downstream of the river Cauvery. The TiO2 content of ilmenites varies from 46.42 to 51.28 wt%, whereas iron oxide values range between 46.35-50.68 wt. %. The detrital ilmenite grains are primary in nature and not subject to any alteration. Bychemistry we can conclude that basic suites are source for the ilmenites in fluvial sediments of river Cauvery.

Seit zehn Jahren veranstalten die Forschungsbibliothek Gotha und das Forschungszentrum Gotha der Universität Erfurt die „Gothaer Kartenwochen“. In diesem Jahr wird die jährlich stattfindende Ausstellung (Kurator: Matthias Rekow) sowie ein Teil des Begleitprogramms vom Sammlungs- und Forschungsverbund Gotha durchgeführt, zu dem sich Forschungsbibliothek und Forschungszentrum mit der Stiftung Schloss Friedenstein Gotha zusammengeschlossen haben. Die Kartenwochen rücken die geodätischen und kartografischen Traditionen Gothas verstärkt in das Bewusstsein der Öffentlichkeit. Bedeutendstes Zeugnis dieser Tradition ist die Sammlung Perthes, die aus dem Firmenarchiv des Verlages Justus Perthes Gotha hervorging. Allein Thüringen betreffend enthält dieser Bestand rund 2.500 Einzelkarten und Kartenwerke.
Anspruch der „Gothaer Kartenwochen“ ist es, den Reichtum und das Potenzial der Gothaer Sammlungen über den engeren wissenschaftlichen Kreis hinaus der Öffentlichkeit bekanntzumachen und neueste Forschungen zu präsentieren. Unter dem Titel „Meridian Gotha. Zur Triangulation und Vermessung Thüringens um 1800“ thematisieren die Kartenwochen die historischen Bemühungen um eine wissenschaftlich fundierte geodätische Erfassung der Region. Eckpunkte bilden dabei die Aktivitäten des Gothaer Herzogs Ernst II. (1745–1804) und seines Astronomen Franz Xaver Freiherr von Zach (1754–1832) in den Jahren von 1786 bis 1804 und die Königlich-Preußische Landesaufnahme der thüringischen Lande von 1851 bis 1857. Der Titel spielt auf die präzise Meridianbestimmung des Passageinstruments in der Sternwarte Seeberg bei Gotha an. Davon ausgehend erkundete Zach eine Basislinie, die Grundlage einer Landesvermessung Thüringens und einer ersten Gradmessung auf deutschem Boden werden sollte.
Auf dem Programm stehen wöchentliche Abendvorträge, Führungen und ein mit dem Landesamt für Vermessung und Geoinformation Erfurt veranstalteter Projekttag für Schülerinnen und Schüler der Sekundarstufen, der einen Einblick in die Praxis und das Berufsfeld von Geodäsie und Kartografie geben wird. Ein internationaler Workshop des Forschungszentrums Gotha in Kooperation mit der École des Hautes Études en Sciences Sociales (EHESS) und der University of Cambridge erweitert die regionale Thematik mithilfe eines vergleichenden Blicks auf außereuropäische Vermessungsvorhaben in Asien.
Umrahmt wird das Programm von einer Ausstellung zur Geschichte der Geodäsie in Thüringen (Kurator: Matthias Rekow). Zu diesem Anlass werden erstmalig einzigartige Funde aus den Beständen der Forschungsbibliothek Gotha, einschließlich der Sammlung Perthes, und des Thüringischen Landesarchivs sowie der Stiftung Schloss Friedenstein Gotha zusammengeführt. Ergänzt werden diese durch attraktive Leihobjekte aus dem Mathematisch-Physikalischen Salon der Staatlichen Kunstsammlungen Dresden und von privaten Leihgebern.

We apply a novel approach for the gravimetric marine geoid modelling which utilise the boundary element method (BEM). The direct BEM formulation for the Laplace equation is applied to obtain a numerical solution to the linearised fixed gravimetric boundary-value problem in points at the Earth's surface. The numerical scheme uses the collocation method with linear basis functions. It involves a discretisation of the Earth's surface which is considered as a fixed boundary. The surface gravity disturbances represent the oblique derivative boundary condition. The BEM approach is applied to determine the marine geoid model over the study area of the Southwest Pacific Ocean and Tasman Sea using DNSC08 marine gravity data. The comparison of the BEM-derived and EGM2008 geoid models reveals that the geoid height differences vary within -25 and 18 cm with the standard deviation of 6 cm. The DNSC08 sea surface topography data and the new marine geoid are then used for modelling of the mean dynamic topography (MDT) over the study area. The local vertical datum (LVD) offsets estimated at 15 tide-gauge stations in New Zealand are finally used for testing the coastal MDT. The average value of differences between the MDT and LVD offsets is 1 cm.

The Australian Height Datum (AHD) is the national vertical datum for Australia, and AUSGeoid09 is the latest quasigeoid model used to compute (normalorthometric) AHD heights from Global Navigation Satellite System (GNSS) derived ellipsoidal heights. While previous studies have evaluated the AUSGeoid09 model across Australia, such studies have generally not focused on mountainous terrain. This paper investigates the performance of AUSGeoid09 in a relative sense in the MidHunter and Snowy Mountains regions of New South Wales, from a user’s perspective. Relative (i.e. height difference between two points) comparisons were undertaken between AUSGeoid09-derived heights and officialAHDheights. The performance of AUSGeoid09 was compared to its predecessor AUSGeoid98. In both study areas, an overall improvement was evident when applying AUSGeoid09 to compute AHD height differences. AUSGeoid09 generally provided AHD height differences at the ±0.05mto ±0.09m level (1 sigma) and substantially ...

Orientation of the Geometrically Best fitting Triaxial Lunar Ellipsoid with Respect to the Mean Earth/Polar Axis Reference FrameThis study provides new estimates for the orientation of a geometrically best fitting lunar triaxial ellipsoid with respect to the mean Earth/polar axis reference frame calculated from the footprint positions of the Chang'E-1 (CE-1), SELenological and ENgineering Explorer (SELENE) laser altimetry measurements and Unified Lunar Control Networks 2005, (ULCN 2005) station coordinates. The semi-principal axes of the triaxial ellipsoid and the coordinates of its geometric center are also calculated simultaneously. All the estimated parameters from all three data sets are found to be consistent. In particular, the RMS differences of the semi-principal axes of the triaxial ellipsoids and the locations of their geometric centers from solutions with and without modeling Euler angles (orientation of the triaxial ellipsoid) using uniformly distributed laser altime...

The impact of the earth’s atmospheric layers, particularly the troposphere on Global Navigation satellite system (GNSS) signals has become a major concern in GNSS accurate positioning, navigation, surveillance and timing applications. For precise GNSS applications, tropospheric delay has to be mitigated as accurately as possible using tropospheric delay prediction models. However, the choice of a particular prediction model can signifi-cantly impair the positioning accuracy particularly when the model does not suit the user’s environment. A performance assessment of these prediction models for a suitable one is very important. In this paper, an assessment study of the performances of five blind tropospheric delay prediction models, the UNB3m, EGNOS, GTrop, GPT2w and GPT3 models was conducted in Ghana over six selected Continuously Operating Reference Stations (CORS) using the 1˚x1˚ gridded Vienna Mapping Function 3 (VMF3) zenith tropospheric delay (ZTD) product as a reference. The g...

The principal limiting error source in the Global Positioning System (GPS) is the mismodeling of the delay experienced by radio waves in propagating through the atmosphere. The atmosphere causing the delay in GPS signals consists of two main layers: the ionosphere and the troposphere. The ionospheric delay can be mitigated using dual frequency receivers, but the tropospheric delay is often corrected using a standard tropospheric model. The tropospheric delay can be described as a product of the delay at the zenith and a mapping function, which models the elevation dependence of the propagation delay. A large number of mapping functions have been developed for use in the analysis of space geodetic data. An assessment of most of these mapping functions including those developed by Niell (NMF), Herring (MTT), Davis (CfA-2.2), Ifadis, Chao, Black & Eisner (B & E), Yang & Ping, Moffett, Vienna (VMF), and Isobaric (IMF) have been performed. The behavior of these mapping functions was asse...

The free geodetic network considered in this work is a free two-dimensional trilateration network which is a set of physical points accessible through occupation, direct or indirect observation that provides to the users of parameters that allows us to know the shape and size of the Earth. The goal of this work is to find a LEast Square Solution (LESS) to the inverse problem of estimate the network points coordinates using the observed distances in an adjustment model of type Gauss- Markov Model (GMM). The positions of the network points are defined in a Local two-dimensional Geodetic Reference System (LGRS) using only Cartesian or plane coordinates (x,y). The LGRS is defined using attributes of a topocentric Terrestrial Reference System TRS described by Boucher,C. (2001) as one of the major types of TRS in use, hence, the LGRS is designated here as Terrestrial Reference Cartesian Coordinate System TRS(x,y).The origin “o” of the TRS(x,y) is on the Earth’s surface and the orientation...

This paper addresses the task of time separated aerial image registration. The ability to solve this problem accurately and reliably is important for a variety of subsequent image understanding applications. The principal challenge lies in the extent and nature of transient appearance variation that a land area can undergo, such as that caused by the change in illumination conditions, seasonal variations, or the occlusion by non-persistent objects (people, cars). Our work introduces several novelties: (i) unlike all previous work on aerial image registration, we approach the problem using a set-based paradigm; (ii) we show how local, pair-wise constraints can be used to enforce a globally good registration using a constraints graph structure; (iii) we show how a simple holistic representation derived from raw aerial images can be used as a basic building block of the constraints graph in a manner which achieves both high registration accuracy and speed. We demonstrate: (i) that the proposed method outperforms the state-of-the-art for pair-wise registration already, achieving greater accuracy and reliability, while at the same time reducing the computational cost of the task; and (ii) that the increase in the number of available images in a set consistently reduces the average registration error.