Geodetic Control Network Research Articles

Key Technology on Constructing Modern Geodetic Control Network in Shandong Province

This document illustrates the overall technical requirements of constructing modern geodetic control net in Shandong. Besides, it discusses the key technology of following aspects: the layout, observation and data processing of A, B and C-order GPS control net; the repetition measurement of second-class level net throughout the entire Shandong; the repetition and filling-in measurement of third-class level net of Shandong; geoid refining. What’s more, it demonstrates the vital significance and expected precision indexes of constructing recent geodetic control net in Shandong.

Progress and prospects in Chinese Antarctic surveying,mapping and remote sensing studies

Antarctic surveying, mapping and remote sensing is one of the important aspects of the Chinese Antarctic geoscienceresearch program that stretch back over 25 years, since the first Chinese National Antarctic Research Expedition (CHINARE) in1984. During the 1980’s, the geodetic datum, height system and absolute gravity datum were established at the Great Wall andZhongshan Stations. Significant contributions have been made by the construction of the Chinese Great Wall, Zhongshan andKunlun Stations in Antarctica. Geodetic control and gravity networks were established in the King George Islands, Grove Mountainsand Dome Argus. An area of more than 200 000 km 2 has been mapped using satellite image data, aerial photogrammetry andin situ data. Permanent GPS stations and tide gauges have been established at both the Great Wall and Zhongshan Stations. Studiesinvolving plate motion, precise satellite orbit determination, the gravity field, sea level change, and various GPS applications foratmospheric studies have been carried out. Based on remote sensing techniques, studies have been undertaken on ice sheet andglacier movements, the distributions of blue ice and ice crevasses, and ice mass balance. Polar digital and visual mapping techniqueshave been introduced, and a polar survey space database has been built. The Chinese polar scientific expedition managementinformation system and Chinese PANDA plan display platform were developed, which provides technical support for Chinesepolar management. Finally, this paper examines prospects for future Chinese Antarctic surveying, mapping and remote sensing.

Positional Accuracy Improvement Using Empirical Analytical Functions

We define as Positional Accuracy Improvement the problem of putting together maps A and B of the same area, with B of higher planimetric accuracy. To do so, all objects in A might have to be slightly moved according to a mathematical transformation. Such transformation might ideally be of a specific type, like analytical or conformal functions. We have developed a theory to find a suitable analytical transformation despite it is not well defined because the only data available is the displacement vectors at a limited number of homologue control points. There exists a similar problem in fluid mechanics devoted on estimating the complete velocity field given just values at a limited number of points. We borrowed some ideas from there and introduced them into the positional accuracy improvement problem. We shall demonstrate that it is possible to numerically estimate an analytic function that resembles the given displacement at control points. As a byproduct, an uncertainty estimation is produced, which might help to detect regions of different lineage. The theory has been applied to rural 1:50.000 cartography of Uruguay while trying to diminish the discrepancies against GNSS readings. After the analytic transformation, the RMSE error diminished from 116 m to 48 m. Other problems with similar math requirements are the transformation between geodetic control networks.

Analysis of accuracy of determination of eccentric point coordinates of the KRAW permanent geodetic station in RTK GPS measuring mode with the application of the NAWGEO service of the ASG-EUPOS system.

Over four years since ASG EUPOS permanent geodetic stations started functioning in Poland, and it can be said that geodetic measurements conducted using GPS technology, and particularly in RTK GPS mode, decidedly increased their share in geodetic works and are still broadening their range. The sanctioning of the new Ordinance of the Minister of Internal A airs and Administration of 9 November 2011 on technical standards of geodesic site and height measurements as well as for processing and transfer of the results of these measurements to the National Geodesic and Cartographic Resource was a very signi cant response to this state of a airs. This ordinance regulates many ma ers related to geodesic measurements and replaces many technical instructions used before it, but most importantly, it de nes the modes and principles of conducting measurements using GPS technology. A great deal of the content relating to measurements using this technology has been taken directly from technical guidelines G-1.12. One of the primary tasks of a geodesist conducting small, traditional site and height measurements is the creation of a geodetic control network. This is done most often by single or multiple measurement of a temporarily marked point (sign) using RTK GPS technology in picket measurement mode. At the same time, the new ordinance imposes the obligation of double measurement of every elements of the geodetic control point. Although it does not de ne the concept of double measurement of each element, based on the cited G-1.12 guidelines, it should be presumed that either measurement of such a point by double receiver initialization or by another measuring set, or measurement and development of observation in post-processing mode is being referred to here. In this case, if the accuracy of RTK GPS measurements

Extraction of the deterministic ingredient of a dynamic geodetic control network

Extraction of the deterministic ingredient of a dynamic geodetic control networkA minimum constraints solution, which resolves the datum defect of a control network, is an arbitrary solution that may result in a systematic error in the estimation of the deformation parameters. This error is not derived from measurements and is usually inconsistent with the geophysical reality. A free network is affected only by errors of measurement and, therefore, a free network is an accepted way of coping with this problem. Study of deformations, which is based on the use of geodetic measurements, is usually performed today by defining a kinematic model. Such a model, when used to describe a complex geophysical environment, can lead to the partial estimation of the deterministic dynamics, which characterize the entire network. These dynamics are themselves expressed in measurements, as the adjustment systems' residuals. The current paper presents an extension of the definition of the parameters that are revalued. This extension enables the cleaning of measurements by means of the extraction of datum elements that have been defined by geodetic measurement. This cleaning minimizes the effects of these elements on the revaluated deformation. The proposed algorithm may be applied to achieve the simultaneous estimation of the physical parameters that define the geophysical activity in the network.

Developing rehabilitation design for the abandoned mine excavations in Central Sardinia, Italy

In central Sardinia, several talc–chlorite–feldspar bodies have long been mined by open-pit operations. The mining activity has deeply modified the original landscape of the Lasasai-Bonucoro area in the district of Orani. Thus, the rehabilitation of this area, in particular the open-pit works that are now occupied by pools filled with ground water from aquifers, should be considered as an overall project of landscape restoration. Particular conditions, such as the constant outflow of good-quality water and the scenic nature of the surrounding countryside, are favourable to the accomplishment of the recovery plan. On the basis of the naturalistic and geographical contexts of the mining area and its surroundings, a few proposals concerning the re-utilisation of these excavations are presented in this article. The preparatory work included the characterisation of the study area with a topographic survey, the establishment of a geodetic control network with global positioning system to describe the morphologic features of the landscape and the representation of the study area using three dimensional analysis and geoprocessing by commercial geographical information system GIS/CAD software. The final step involved the use of a digital scenery generator, capable of integrating graphical data layers with geological and morphological maps, to create virtual 3D environments thereby giving a rendering of a present, past and future landscape development.

Accuracy of Static Differential GPS Techniques; Implications for Structural Deformation Monitoring

In recent years, the need to monitor for Deformation in Engineering Structures such as Dams, Bridges and Tall buildings have become more necessary as a result of reported failures of many of these structures with catastrophic consequences globally. Global Positioning System (GPS) is highly automated and less labour intensive than other conventional techniques used in structural deformation monitoring. For most applications, such as National Geodetic Control Network, Urban Control Network and other Engineering Control Network, an accuracy in the cm level for most GPS work is quite adequate. For Structural deformation monitoring however, the required accuracy is in millimeters. In this paper, the use of Static Differential GPS method with multiple receivers for high precision measurement was investigated using the monitoring Stations at Ikpoba Dam as case study Scenerio. Four units of LEICA 300 Dual Frequency GPS receivers were deployed for code and carrier phase measurements with observation session of 1hr at a sampling rate of 15 sec. Baseline Processing and Least Squares Adjustment of observation was carried out in WGS 84 and NTM reference frames using the LEICA SKI-PRO Processing software and Move. Analysis of the results revealed that the number of outliers in the observation were <5% and the accuracy of horizontal and vertical coordinates were 4mm maximum for horizontal and 2mm maximum for vertical. The study revealed that in areas with favourable satellite constellation and appropriate reduction or elimination of multipath and other noise like errors, Static Differential GPS techniques with a combination of code and carrier phase measurement gives good results for structural deformation monitoring.

Monitoring Deformation of Thai Geodetic Network due to the 2004 Sumatra-Andaman and 2005 Nias Earthquakes by GPS

The Thai geodetic network has been regularly observed with GPS since 1994. The continuous tectonic motions in Thailand located on the Sundaland block are well determined with uncertainties ∼1mm∕yr. The mega thrust earthquake occurred near Banda-Aceh on Dec. 26, 2004 with Mw 9.3 magnitude and caused significant surface displacements in many surrounding countries. The geodetic network within Thailand was also significantly deformed during the earthquake at the cm to dm level and the geodetic network will continue to deform for many months and possibly even years to come. The magnitude of displacements certainly has a direct impact on the Thai geodetic control network. The Royal Thai Survey Department (RTSD) has been carrying out GPS field campaigns in an attempt to monitor the postseismic displacement. However, the situation became more complicated when the second major earthquake occurred near Nias Island, Sumatra on Mar. 28, 2005 with Mw 8.7 magnitude. This paper will analyze the GPS observations obtained from the RTSD GPS campaigns and existing permanent GPS stations in Thailand up to the end of 2006 using the precise point positioning strategy of the GIPSY-OASIS II software. Results obtained from the latest campaign (Nov. 2006) indicated that the earthquakes have resulted in the horizontal displacements, ranging from 55cm in the south to about 6cm in the north of Thailand. The behavior of postseismic motions is investigated in this study and it was found that the postseismic motions can be fitted well by a logarithmic decay function. Finally, a strategy for updating the Thai geodetic network is proposed.

How well can online GPS PPP post-processing services be used to establish geodetic survey control networks?

Establishing geodetic control networks for subsequent surveys can be a costly business, even when using GPS. Multiple stations should be occu- pied simultaneously and post-processed with scien- tific software. However, the free availability of online GPS precise point positioning (PPP) post-processing services oer the opportunity to establish a whole geodetic control network with just one dual- frequency receiver and one field crew. To test this idea, we compared coordinates from a moderate- sized (P550 km byP440 km) geodetic network of 46 points over part of south-western Western Australia, which were processed both with the Bernese v5 scien- tific software and with the CSRS (Canadian Spatial Reference System) PPP free online service. After re- jection of five stations where the antenna type was not recognised by CSRS, the PPP solutions agreed on average with the Bernese solutions to 3.3 mm in east, 4.8 mm in north and 11.8 mm in height. The average standard deviations of the Bernese solutions were 1.0 mm in east, 1.2 mm in north and 6.2 mm in height, whereas for CSRS they were 3.9 mm in east, 1.9 mm in north and 7.8 mm in height, reflect- ing the inherently lower precision of PPP. However, at the 99% confidence level, only one CSRS solution was statistically dierent to the Bernese solution in the north component, due to a data interruption at that site. Nevertheless, PPP can still be used to estab- lish geodetic survey control, albeit with a slightly lower quality because of the larger standard devia- tions. This approach may be of particular benefit in developing countries or remote regions, where geo- detic infrastructure is sparse and would not normally be established without this approach.

Geodetic height determination in 2005 Qomolangma survey

Determining the geodetic height of Mount Qomolangma was one of the very important missions in the 2005 Qomolangma height survey. There were three GPS networks in the survey: regional GPS crustal deformation network, geodetic GPS control network, and GPS measurement on the mountain summit. Data collection and processing were introduced. The final data processing strategy and reasonable geodetic height were fairly determined based on careful data analysis.

The Use of GPSSIT (GPS Virtual Station Technique) With Total Station for the Measurement of Details in Residential Areas

GPS become one of the most important tools used in several surveying missions during last one and half decade. It is confidently and intensively used in several surveying tasks from establishment of precise geodetic control networks to the measurement of features and details on land. To fulfill those tasks, there are several techniques that GPS suggests and are available to be used according to the required precision and the requirements of special applications. Under this concept, these GPS techniques can be stated as static, kinematic, semi-kinematic and on the other hand, with respect to the special precision requirements of different applications, they can also be stated as relative, absolute and DGPS techniques. Even if GPS ease the surveying processes for these applications when we use GPS, GPS can some times put forward some limitations. Therefore, it can be said here that GPS has still some difficulties and limitations especially when GPS signals are blocked by some obstacles such as buildings in urban areas. Therefore, one can experience with those cases frequently during the detail measurements in an urban area. Tall buildings, trees and etc in an urban environment can be the main constraints that can cause those GPS signal blockages. Here in this paper, it is argued if a technique is available and allows us to use GPS even for measuring those urban details without worrying about GPS signal blockages.GPSSIT is a technique that can provide this opportunity. So, any measurement process which uses GPS to collect details in an open land by utilizing GPS measurement method that does not need established control into the ground, can be carried out even in residential areas without worrying about the established ground controls.The paper introduces the technique and shows the test results with a standard deviation of ±4.84 cm obtained from the test carried out in the campus area of Selcuk University.

Use of Global Positioning System in mine landscaping and visual impact assessment: A case study

The satellite-based Global Positioning System (GPS) needs a clear view of sky for determining a geodetic position and hence it is particularly suitable in overall projects of open-pit recovery and landscape restoration. The purpose of such measurements is to make highly accurate topographic maps thus forming the backbone of a project. In the work presented here geodetic measurements are combined with advanced visualisation techniques and GIS applications in a possible recovery plan of the abandoned excavations of Bonucoro in the mining district of Orani, central Sardinia, Italy. Considering the naturalistic and geographic settings of the mining area and its surroundings, a few proposals concerning the re-utilisation of these excavations are presented. The preparatory work consisted of the area characterisation by carrying out a topographic survey followed by a geodetic control network establishment by the GPS to describe the morphological features of the landscape and for the subsequent three-dimensional analysis and geoprocessing. The final step involved the use of VueInfinite, a computer program capable to integrate graphical data with geological and morphological attributes. It was also able to create a virtual 3D scene of a present, past, or future landscape required for visual impact assessment.

MODELLING LANDSLIDE SURFACES BY KINEMATIC AND DYNAMIC SURFACE MODELS: A CASE STUDY IN NORTH EASTERN TURKEY

Landslides occurring over time can be visually monitored by surface models. In addition, point movements that have not been measured can be determined with these models using extrapolation. There are several surface models including kinematic and dynamic. In the kinematic surface model, the surface is determined as dependent on time. In the dynamic surface model, the surface is determined regarding cause of movement in addition to time. Landslides are not simple two-dimensional features but have a three-dimensional form and a complicated temporal context. They are dynamic systems that are complex in time and space. Therefore, in this study, a dynamic surface model regarding the cause of landslides was developed to monitor landslides and determine movement surface.Kutlugün Village, a landslide-prone area in Maçka County in the Province of Trabzon in Eastern Black Sea Region of Turkey, was selected for the study. Geological and geophysical investigations were made and it was determined that the change in the groundwater level was the most important cause of landslides. Groundwater level changes were taken into account in the formation of the dynamic surface model. Groundwater levels were measured at three bore holes and at two geophysical points. In addition, a geodetic control network covering the whole region and its surroundings was established. The point coordinates were determined by GPS. Using this data, a dynamic surface model was developed. The model includes computations of surface coefficients and groundwater effect coefficients. Through this model, dynamic surfaces were determined for the measurement periods. For the same measurements periods, kinematic surfaces were also determined. The results derived from both models were compared. It can be seen that groundwater changes affected surface changes. These surface changes which occurred over time were determined more realistic by the dynamic surface model.

Data Processing and Accuracy Analysis of National 2000' GPS Geodetic Control Network

The original data from a number of GPS campaigns carried out in the last 10 years are aggregated to construct the National 2000' GPS Geodetic Control Network and the positions of 2482 GPS sites at 2000.0 epoch with respect to the International Terrestrial Reference Frame (ITRF) are obtained. In this paper, we introduce the method for processing GPS data, deriving site velocities from GPS data, establishing the crustal motion velocity field of the Chinese mainland, and carrying out the network integrated adjustment employing a Kalman filter. The accuracy analysis of GPS daily solutions and final coordinate solutions are presented. A series of technical steps have ensured the rationality and reliability of our results.

POLYNOMIAL VERSUS SIMILARITY TRANSFORMATIONS BETWEEN GPS AND TURKISH REFERENCE SYSTEMS

Efforts to utilize GPS have increased and come a long way in recent years. GPS (Global Positioning System) is the most modern and reliable technique for surveying geodetic control networks. By using relative static GPS observation, it is possible routinely to obtain sub-centimetre positional accuracy for points in geodetic control networks. GPS uses WGS84 (World Geodetic System 1984) as its reference frame. Point position on the earth is obtained by GPS observation in this frame. However, in geodetic and engineering applications, different coordinate systems are used as local or national systems. Combination of GPS networks with the national coordinate system requires determination of the transformation parameters between WGS84 (or ITRF) and the relevant national coordinate system. Several models can be used for transformation. The main purpose of this research is examination of 2 and 3D polynomial transformation models instead of 2 and 3D similarity transformations for distorted networks. However, the study also aims to determine reliable transformation parameters between ITRF94 and Turkish National Reference frame ED50 for Istanbul.

Global Positioning System and Strengthening of Geodetic Network of Nepal

Nepal is a country of mountains The higher order geodetic points were mostly established on the top of mountains and these points were used for the geodetic network extension. Lower order geodetic control networks were established at different times and used for the surveying and mapping activities of the country. It has been found that the rate of convergence between north and south borders of Nepal to be 21±2 mm each year and the rate translation of Kathmandu to 55±3 mm/year to the plates. The most intense deformation in Nepal occurs along the belt of high mountains along its northern border resulting in a strain contraction rate normal to the Himalayan Arc. This belt is approximately 40 km wide and extends into southern Tibet.( 13). Recently Survey Department of Nepal has lunched a program of strengthening the existing geodetic network of Nepal and re-observed the position of higher order geodetic points by using geodetic GPS receivers to evaluate their position and thus to define the precision of the control points once again. This paper describes the observation procedure and the adjustment results of the existing higher order control network of Nepal established in different time using different types of equipment and techniques; and highlights the observation procedure and the result obtained after the post processing of the GPS observation results. Attempt has been made to give the procedure and identify the methodology for the re observation of existing higher order geodetic points by using GPS receiver and post processing the observed data so that the existing higher order geodetic points are within the given accuracy standard.

Stability of the points of the Hungarian geodetic control networks

Following a short historical survey of the Hungarian geodetic control networks the author analyses four Hungarian networks measured after the introduction of the Schreiber angle measurement method (1878), namely those measured by the Milit\ärgeographisches Institut Wien (1878-1899), the first order network in Transdanubia measured in 1901-1908, the new triangulation network measured in 1925-1942 and the network HD72 started in 1950. The presented results are Ferrero's mean square angular errors (Table I), comparison of the form of the networks, determination of the co-ordinate differences of the point transfers (Table II), then for identical points the comparison of direction measurements from the station adjustment (Tables III-VIII). The conclusion of this study is that historical Hungarian triangulation measurements are not applicable for the detection of exact point movements.

CRUSTAL DEFORMATIONS FROM SPARCE GEODETIC DATA

During the last decade, the Higher Geodesy Laboratory of NTU and the Seismology Department of the Institut de Physique du Globe de Paris have carried out a research program concerning the evaluation of the tectonic behaviour of the Gulf of Corinth, in Greece, based on geodetic data. The area being one of the densely populated, seismically active parts of Greece, was considered suitable for monitoring deformations. Thus, a geodetic GPS control network of 193 points, spread over a broad area (of about 10000 km2) on both sides of the Gulf, was established within seven years. During this period several points were reoccupied. Thus the GPS data acquired are sparse both in space and time. In order to estimate the deformation over longer periods of time 142 of the network points were chosen to belong to the Hellenic triangulation network. In the present paper, statistically acceptable strain parameters are evaluated via a multi-epoch deformation model using GPS data alone as well as in combination with positional information from old geodetic surveys.

CRUSTAL DEFORMATIONS FROM SPARCE GEODETIC DATA

During the last decade, the Higher Geodesy Laboratory of NTU and the Seismology Department of the Institut de Physique du Globe de Paris have carried out a research program concerning the evaluation of the tectonic behaviour of the Gulf of Corinth, in Greece, based on geodetic data. The area being one of the densely populated, seismically active parts of Greece, was considered suitable for monitoring deformations. Thus, a geodetic GPS control network of 193 points, spread over a broad area (of about 10000 km2) on both sides of the Gulf, was established within seven years. During this period several points were reoccupied. Thus the GPS data acquired are sparse both in space and time. In order to estimate the deformation over longer periods of time 142 of the network points were chosen to belong to the Hellenic triangulation network. In the present paper, statistically acceptable strain parameters are evaluated via a multi-epoch deformation model using GPS data alone as well as in combination with positional information from old geodetic surveys.

Applications of graph theory to gross error detection for GPS geodetic control networks

This paper describes a broad perspective of the application of graph theory to establishment of GPS control networks whereby the GPS network is considered as a connected and directed graph with three components. In this algorithm the gross error detection is undertaken through loops of different spanning trees using the “Loop Law” in which the individual components ΔX, ΔY and ΔZ sum up to zero. If the sum of the respective vector components ΩX, ΩY and ΩZ in a loop is not zero and if the error is beyond the tolerable limit (ε>ω), it indicates the existence of gross errors in one of the baselines in the loop and therefore the baseline must be removed or re-observed. After successful screening of errors by graph theory, network adjustment can be carried out. In this paper, the GPS data from the control network established as refence system for the HP Dam at Baishan county in Liaoning province is presented to illustrate the algorithm.