Geodetic Control Research Articles

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.

Geometrically accurate time series of archived aerial images and airborne lidar data in a forest environment

Reconstructing three-dimensional structural changes in the forest over time is possible using archived aerial photographs and photogrammetric techniques, which have recently been introduced to a larger audience with the advent of digital photogrammetry. This paper explores the feasibility of constructing an accurate time-series of archived aerial photographs spanning 42 years using different types of geometric data and estimation methods for image orientation. A recent airborne laser scanning (lidar) data set was combined with the image block and assessed for geometric match. The results suggest that it is possible to establish the multitemporal geometry of an image block to an accuracy that is better than 0.5 m in 3D and constant over time. Even geodetic ground control points can be omitted from the estimation if the most recent images have accurate direct sensor orientation, which is becoming a standard technique in aerial photography. This greatly reduces the costs and facilitates the work. An accurate multitemporal image block combined with recent lidar scanning for the estimation of topography allows accurate monitoring and retrospective analysis of forest vegetation and management operations.

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.

Geodetic Control of Structures of the Bratsk Hydropower Plant

Geodetic Control of Structures of the Bratsk Hydropower Plant

Seasonal to Interannual Morphodynamics along a High-Energy Dissipative Littoral Cell

RUGGIERO, P.; KAMINSKY, G.M.; GELFENBAUM, G., and VOIGT, B., 2005. Seasonal to interannual morphodynamics along a high-energy dissipative littoral cell. Journal of Coastal Research, 21(3), 553‐578. West Palm Beach (Florida), ISSN 0749-0208. A beach morphology monitoring program was initiated during summer 1997 along the Columbia River littoral cell (CRLC) on the coasts of northwest Oregon and southwest Washington, USA. This field program documents the seasonal through interannual morphological variability of these high-energy dissipative beaches over a variety of spatial scales. Following the installation of a dense network of geodetic control monuments, a nested sampling scheme consisting of cross-shore topographic beach profiles, three-dimensional topographic beach surface maps, nearshore bathymetric surveys, and sediment size distribution analyses was initiated. Beach monitoring is being conducted with stateof-the-art real-time kinematic differential global positioning system survey methods that combine both high accuracy and speed of measurement. Sampling methods resolve variability in beach morphology at alongshore length scales of approximately 10 meters to approximately 100 kilometers and cross-shore length scales of approximately 1 meter to approximately 2 kilometers. During the winter of 1997/1998, coastal change in the US Pacific Northwest was greatly

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.

Exploitation of Very High Resolution Satellite Data for Tree Species Identification

With the emergence of very high spatial resolution satellite images, the spatial resolution gap which existed between satellite images and aerial photographs has decreased. A study of the potential of these images for tree species in “monoculture stands” identification was conducted. Two Ikonos images were acquired, one in June 2000 and the other in October 2000, for an 11- by 11-km area covering the Sonian Forest in the southeastern part of the Brussels-Capital region (Belgium). The two images were orthorectified using a digital elevation model and 1256 geodetic control points. The identification of the tree species was carried out utilizing a supervised maximum-likelihood classification on a pixel-by-pixel basis. Classifications were performed on the orthorectified data, NDVI transformed data, and principal components imagery. In order to decrease the intraclass variance, a mean filter was applied to all the spectral bands and neo-channels used in the classification process. Training and validation areas were selected and digitized using detailed geographical databases of the tree species. The selection of the relevant bands and neo-channels was carried out by successive addition of information in order to improve the classification results. Seven different tree species of one to two different age classes were identified with an overall accuracy of 86 percent. The seven identified tree species or species groups are Oaks (Quercus sp.), Beech (Fagus sylvatica L.), Purple Beech (Fagus sylvatica purpurea), Douglas Fir (Pseudotsuga menziesii (Mirb.) Franco), Scots Pine (Pinus sylvestris L.), Corsican Pine (Pinus nigra Arn. subsp. laricio (Poir.) Maire var. corsican), and Larch (Larix decidua Mill.).

Predicting Missing Field Boundaries to Increase Per-Field Classification Accuracy

With the emergence of very high spatial resolution satellite images, the spatial resolution gap which existed between satellite images and aerial photographs has decreased. A study of the potential of these images for tree species monoculture stands identification was conducted. Two Ikonos images were acquired, one in June 2000 and the other in October 2000, for an 11- by 11-km area covering the Sonian Forest in the southeastern part of the Brussels-Capital region (Belgium). The two images were orthorectified using a digital elevation model and 1256 geodetic control points. The identification of the tree species was carried out utilizing a supervised maximum-likelihood classification on a pixel-by-pixel basis. Classifications were performed on the orthorectified data, NDVI transformed data, and principal components imagery. In order to decrease the intraclass variance, a mean filter was applied to all the spectral bands and neo-channels used in the classification process. Training and validation areas were selected and digitized using detailed geographical databases of the tree species. The selection of the relevant bands and neo-channels was carried out by successive addition of information in order to improve the classification results. Seven different tree species of one to two different age classes were identified with an overall accuracy of 86 percent. The seven identified tree species or species groups are Oaks (Quercus sp.), Beech (Fagus sylvatica L.), Purple Beech (Fagus sylvatica purpurea), Douglas Fir (Pseudotsuga menziesii (Mirb.) Franco), Scots Pine (Pinus sylvestris L.), Corsican Pine (Pinus nigra Arn. subsp. laricio (Poir.) Maire var. corsican), and Larch (Larix decidua Mill.).

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.

Monitoring Crustal Movements in West Anatolia by Precision Leveling

In a previous study, the author investigated the best suited static and kinematic models for deformation analysis. In that study, the best results were obtained with the Kalman-filtering technique for the kinematic model. In addition, the best kinematic surface model was determined. In this study, the conclusions of the previous work have been tested in the city of Aydin in the West Anatolia region of Turkey. Because the crustal movements are very slow, periodic observations have to be performed in the longterm. In addition, such observations have to be done with high precision. For this, precision leveling has been preferred for this study. Precision leveling data were already in place from the observations made each year from 1978 to 1985 in the West Anatolian city of Aydin. From this data, the vertical crustal movements have been determined using the best static and kinematic models determined by the author’s previous work. In conclusion, the average movements of geodetic control points have been deter...

Transfer of vertical geodetic control using only one GPS receiver: a case study

Abstract Normally, the precise transfer of vertical geodetic control by GPS requires two receivers operating simultaneously in carrier-phase mode. This paper describes the transfer of vertical control into areas that have sparse existing geodetic control using only a single GPS receiver. The GPS data were processed using the Australian Surveying and Land Information Group's (AUSLIG's) AUSPOS on-line GPS processing facility (www.auslig.gov.au/geodesy/sgc/wwwgps/wwwgps.htm). These GPS-estimated ellipsoidal heights were transformed to the Australian Height Datum (AHD) using AUSGeoid98. In the case study area of Western Australia, a small bias had to be applied to account for the absolute difference between AUSGeoid98 and the AHD before the detailed spirit-levelling traverses, tied to these single-GPS-derived heights, were integrated with a digital elevation model.

Transfer of vertical geodetic control using only one GPS receiver: a case study

Transfer of vertical geodetic control using only one GPS receiver: a case study

EVALUATION PRACTICE ON AIRBORNE GPS DATA QUALITY

Since July 1,1991 the GPS signals transmitted by each satellite have been activated by the Selective Availability (SA) techniques that mean unauthorized users can only acquire 120m-accuracy qf real-time positions. To match air photogrammetric engineering we have developed successffully an airborne GPS kinematic carrier phase measurement technique, with new software based on the Kalman filter processing for pseudorange/double difference data of carrier phase measurements, and can complete the ambiguity resolution On The Fly(0TF) on the carrier phase measurements, defining as DDKlN software. DDKlN was used to solve precisely for seven dimension state parameters of 10 types of aircraft making over 200 flights between 1994 and 2000. It is known from the analysis using 103 ground geodetic controls with millimetre accuracy, that the coordinate accuracies of Trimble 4000SST receiver installed in the aircraft have achieved ± 7.9 cm for 2D positions and ± 18.1 cm for heights above the ground. This paper discusses only three evaluations: kinematic figuration check, flight velocity evaluation and dual initialization evaluation.

Geodetic control on recent tectonic movements in the central Mediterranean area

During the Neogene and Quaternary, the western Mediterranean geodynamics was apparently dominated by the nearly eastward migration of the Apenninic arc and the associated opening (spreading) of the back-arc basin (Tyrrhenian Sea). However, during the last 5 My, the collision of the arc with the Apulian platform led to a dramatic change in the tectonic setting of the area. As geological processes require a long period of time to register the displacements of the different blocks, it is indispensable to take into account the present-day motion given by space geodesy data analysis in order to better constrain the geological models. Geodetic motions were derived from Global Positioning System (GPS), Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) observations collected from different networks. All the geodetic solutions have been computed and combined at the Centre of Space Geodesy (CGS), at Matera, Italy. The geodetic results show a NNE motion of the Adriatic plate with a small component of counter-clockwise rotation, in good agreement with the geological and geophysical observations. In the southern Tyrrhenian area, the lengthening of the Matera–Cagliari baseline should imply that convergence cannot be considered as the driving mechanism for the Apenninic subduction process. The estimated motion of Noto is in quite good agreement with the estimated motion of the African plate.