GNSS Techniques Research Articles

A global grid model for calibration of zenith hydrostatic delay

The determination of zenith hydrostatic delay (ZHD) is a key step to obtain water vapor information using GNSS technique, and it can be used to separate zenith wet delay (ZWD) with high accuracy from GNSS measurements. Estimates of ZHD are generally of higher accuracy when obtained from accurate pressure information and using the Saastamoinen model rather than when obtained from climatology. To improve this model, we analyzed the differences between the integrated ZHD and the Saastamoinen modeled ZHD, explored the relationship between the ZHD differences and meteorological parameters, and proposed a calibration model based on a global 2.5°×2° grid using the 5 years of pressure levels from the ERA5 reanalysis data provided by European Center for Medium-Range Weather Forecasts (ECMWF). The performance of the calibration model was assessed against the Saastamoinen model using different data sources in 2016, i.e., the ERA5 data and globally distributed radiosonde data. The numerical results show that the calibration model outperforms the Saastamoinen model with a global 59%/89% improvement of RMSE and bias in the ECMWF comparison. In comparison with the radiosonde data, the mean bias/RMSE of the calibration model improves by 5.14/3.24, 1.73/1.47 and 3.15/2.84 mm against the Saastamoinen model in the latitude zones of <30°, 30–60°, and >60°, respectively.

A novel ENSO monitoring index and its potential for drought application

The El Niño–Southern Oscillation (ENSO) changes the air flow in the tropics, causing global droughts, floods, typhoons, and other natural disasters. Therefore, monitoring and forecasting of ENSO events effectively play an important role in disaster prevention and mitigation. This paper proposes a novel ENSO monitoring index using GNSS-derived zenith tropospheric delay (ZTD) and temperature (T), which is called the standardized ENSO monitoring index (SEMI), and validated its performance by introducing the standardized precipitation evapotranspiration index (SPEI). Multichannel singular spectral analysis (MSSA) and Lomb-Scargle periodogram are first applied to determine the periodic signals of ZTD and T. Empirical Orthogonal Function (EOF) is then used to analyze the spatio-temporal characteristics of ZTD and T. Finally, the response thresholds of ZTD and T to ENSO events are determined using the moving window correlation analysis (MWCA) method, and the SEMI is established based on the relationship between abnormal changes of sea surface temperature anomaly (SSTa) and ZTD/T. ZTD and T of 97 GNSS stations and the corresponding SPEI over the period of 2006–2016 in Taiwan province has been obtained to validate the capacity of the proposed SEMI for ENSO monitoring. Experimental results reveal that (1) annual and semi-annual periods existed in ZTD and T with the values of 365.25 and 182.625 days, respectively. (2) ZTD and T have good correlations with SSTa, and the coefficients are 0.64 and 0.70, respectively. (3) The response thresholds of ZTD and T to ENSO events in Taiwan province are [−1.13 °C, 0.84 °C] and [−1.09 °C, 0.69 °C], respectively. (4) The proposed SEMI has a good relationship with SSTa with a correlation coefficient of 0.77 and has been proven to have good ENSO monitoring capacity by comparing with SPEI with a correlation coefficient of 0.83. This result is of great significance for drought and flood disaster monitoring by the GNSS technique.

GNSS and RPAS Integration Techniques for Studying Landslide Dynamics: Application to the Areas of Victoria and Colinas Lojanas, (Loja, Ecuador)

This research tests the application of GNSS and RPAS techniques to the spatiotemporal analysis of landslide dynamics. Our method began by establishing non-permanent GNSS networks on the slope surfaces to perform periodic measurements by differential GNSS. Similarly, RPAS flights were made to acquire high-resolution images, which were oriented and georeferenced using ground control points and structure-from-motion algorithms to ultimately obtain digital surface models and orthophotos. Based on GNSS measurements, the direction and velocity of displacements were accurately calculated, and orthophotos and DSMs were used to calculate horizontal and vertical displacements in a set of significant points throughout the study area, reaching accuracies higher than 0.035 m in the GNSS data and 0.10 m in the RPAS data. These values were within the accuracy required for such studies. Based on the field observations and the results from the photogrammetric studies, the two studied landslides were classified as very slow flows. These techniques are the basis for establishing early warning systems in areas of natural hazards based on the calculation of displacement speeds of the surface of slopes.

Evaluation of quasi-geoid model based on astrogeodetic measurements: case of Latvia

AbstractSince the development of GNSS techniques, the determination of a precise quasi-geoid model has become even more actual. In terms of this project the staff of the Institute of Geodesy and Geoinformatics (GGI) has developed a new quasi-geoid model based on DFHRS (Digital Finite-element Height Reference Surface) approach additionally using astrogeodetic measurements – vertical deflections (VD), which can be observed by a Digital zenith camera. This paper evaluates a quasi-geoid model results based on vertical deflections, as a study area using the territory of Latvia: the standard deviation of the solution is equal to 0.006 m with observation residuals after the adjustment of minimum and maximum differences −0.012 and 0.012 accordingly. The standard deviation of quasi-geoid heights and h-H values from LGIA database is equal to 0.012 m with minimum and maximum differences −0.026 and 0.025 accordingly. The post-processed terrestrial VD observations have been compared to VD derivatives from EGM2008 and GGMplus geopotential models. The developed quasi-geoid has been compared to the national quasi-geoid model LV’14 and to the Scandinavian NKG2015.

Monitoring deformations of Istanbul metro line stations through Sentinel-1 and levelling observations

Turkey, as a developing country, is designing and performing massive construction projects around Istanbul. Beginning from the 1960s, rapid urbanization has been taking place due to industrialization, which brings an increase in the population. Yet, construction projects have been accelerated especially during the last decade, and many new projects are scheduled to be completed in a short time. Ground-based observations are generally carried out to monitor the deformations within construction sites, especially through geometric levelling, and GNSS techniques. However, in most cases, these monitoring measurements are only scheduled within the period of the construction process, and ensuing deformations are usually not considered. In addition to these techniques, the space-based interferometric technique can also be used to define the line of sight surface displacements with high accuracy, using the phase difference between image result for synthetic aperture radar images. In particular, Persistent Scatter Interferometry is one of the interferometric methods that are capable of defining the two-dimensional (vertical and horizontal) deformation for the desired epoch with a high temporal resolution. Thus it can be used as a complementary method for monitoring ground deformations, where the measurement is made by ground-based observations. In this study, the deforming areas related to underground metro construction are investigated through significant displacements between 2015 and 2018 of Sentinel-1 space-borne SAR data using the PSI technique. These results are validated by comparison with available levelling data corresponding to the new metro line.

An Investigation on the Performance of Soft Computing Techniques for Point Displacement Modeling for Suspension Bridge Using GNSS Technique

Bridges are playing a major role in the socio-economic development of any country over the world. Suspension bridges are one of the most sensitive structures to various external influences and loads. Therefore, the need for structural monitoring system, maintenance and deformation prediction for these types of structures is important and vital. Time of observations for the purpose of structural deformation can vary from a few hours, days to several months or even years. This paper investigates the performance of several soft computing techniques for point displacement modeling using GNSS technique during the process of monitoring the structural deformation of suspension highway bridge, taking into consideration the effect of wind, temperature, humidity and traffic loads during the operational and short-term measurements. Due to the availability of a large amount of positions data generated from GNSS data positions for monitoring the deformation of such structure, artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS) should be chosen. One of the main objectives of this paper is to investigate the optimum predictive soft computing model for processing GNSS positions and points displacement prediction. Several mathematical models and two cases of data amount (66.67% and 50% of all available data) for dynamic and kinematic state are applied and compared for prediction of suspension bridge displacement with confidence interval with a probability ρ = 0.95, Δ = ± 2σ. The resulting point displacement values by applying ANNs and ANFIS, which used a confidence interval with a probability of ρ = 0.95, Δ = ± 2σ when using 66.67% of all data, are more accurate and reliable than any other applied methods, and therefore, ANNs and ANFIS can provide a significant improvement of understanding and predicting the structure deformation values where conventional mathematical modeling techniques were not as accurate or capable especially in dynamic prediction of displacements.

Global equivalent slab thickness model of the Earth’s ionosphere

The shape of the vertical electron density profile is a result of production, loss and transportation of plasma in the Earth’s ionosphere. Therefore, the equivalent slab thickness of the ionosphere that characterizes the width of vertical electron density profiles is an important parameter for a better understanding of ionospheric processes under regular as well as under perturbed conditions. The equivalent slab thickness is defined by the ratio of the vertical total electron content over the peak electron density and is therefore easy to compute by utilizing powerful data sources nowadays available thanks to ground and space based GNSS techniques. Here we use peak electron density data from three low earth orbiting (LEO) satellite missions, namely CHAMP, GRACE and FORMOSAT-3/COSMIC, as well as total electron content data obtained from numerous GNSS ground stations. For the first time, we present a global model of the equivalent slab thickness (Neustrelitz equivalent Slab Thickness Model – NSTM). The model approach is similar to a family of former model approaches successfully applied for total electron content (TEC), peak electron density NmF2 and corresponding height hmF2 at DLR. The model description focuses on an overall view of the behaviour of the equivalent slab thickness as a function of local time, season, geographic/geomagnetic location and solar activity on a global scale. In conclusion, the model agrees quite well with the overall observation data within a RMS range of 70 km. There is generally a good correlation with solar heat input that varies with local time, season and level of solar activity. However, under non-equilibrium conditions, plasma transport processes dominate the behaviour of the equivalent slab thickness. It is assumed that night-time plasmasphere–ionosphere coupling causes enhanced equivalent slab thickness values like the pre-sunrise enhancement. The overall fit provides consistent results with the mid-latitude bulge (MLB) of the equivalent slab thickness, described for the first time in this paper. Furthermore, the model recreates quite well ionospheric anomalies such as the Night-time Winter Anomaly (NWA) which is closely related to the Mid-latitude Summer Night-time Anomaly (MSNA) like the Weddell Sea Anomaly (WSA) and Okhotsk Sea Anomaly (OSA). Further model improvements can be achieved by using an extended model approach and considering the particular geomagnetic field structure.

The performance assessment of Precise Point Positioning (PPP) under various observation conditions

Two different methods, absolute and relative positioning, are used in determining point positions with GNSS techniques. Precise Point Positioning (PPP) technique, which is one of the absolute positioning methods, is a powerful position determination method.In this study, the accuracy of PPP has been investigated in terms of session durations, online web services, satellite visibility and urbanization. For this purpose, three of CORS-Tr stations were selected in residential, semi-residential and non-residential areas. Consecutive 31-day data of these stations for the year 2019 were downloaded from server. The 31-day consecutive coordinates were obtained by sending the downloaded RINEX data to AUSPOS. The average of these coordinates was considered as true quantity value. Then, the RINEX data were binned four groups as 1 h, 2 h, 4 h, 6 h. The binned data were evaluated with web-based online PPP services (CSRS-PPP, magicGNSS, APPS) and compared with the true quantity value. In conclusion, it was seen that the best result was obtained in the non-residential area and CSRS-PPP yielded the most accurate results for all session durations.

An Analysis of the Eurasian Tectonic Plate Motion Parameters Based on GNSS Stations Positions in ITRF2014.

The article is the fourth part of our research program concerning an analysis of tectonic plates’ motion parameters that is based on an observation campaign of an array of satellite techniques: SLR, DORIS, VLBI, and now GNSS. In this paper, based on the International Terrestrial Reference Frame 2014 (ITRF2014) for observations and using the GNSS technique, the Eurasian tectonic plate motion was analyzed and the plate motion parameters Φ, Λ (the position of the rotation pole), and ω (the angular rotation speed) were adjusted. Approximately 1000 station positions and velocities globally were obtained from the GNSS campaign over a 21-year time interval and used in ITRF2014. Due to the large number of data generated using this technique, the analyses were conducted separately for each tectonic plate. These baseline data were divided into a number of parts related to the Eurasian plate, and are shown in this paper. The tectonic plate model was analyzed on the basis of approximately 130 GNSS station positions. A large number of estimated station positions allowed a detailed study to be undertaken. Stations that agree with the plate motion were selected and plate parameters were estimated with high accuracy. In addition, stations which did not agree with the tectonic plate motion were identified and removed. In the current paper, the influence of the number and location of stations on the computed values and accuracy of the tectonic plate motion parameters is discussed. Four calculation scenarios are examined. Each scenario contains 30 stations for the common solution of the European and Asiatic part of the Eurasian plate. The maximum difference between the four calculation scenarios is 0.31° for the Φ parameter and 0.24° for the Λ parameter, indicating that it is at the level of the value of the formal error. The ω parameter has the same value for all the scenarios. The final stage of the analysis is the estimation of parameters Φ, Λ, and ω based on all of the 120 stations used in the four calculation scenarios (i.e., scenario 1 + scenario 2 + scenario 3 + scenario 4). The following results are obtained: Φ = 54.81° ± 0.37°, Λ = 261.04° ± 0.48°, and ω = 0.2585°/Ma ± 0.0025°/Ma. The results of the analysis are compared with the APKIM2005 model and another solution based on the GNSS technique, and a good agreement is found.

Epoch-by-epoch phase difference method to evaluate GNSS single-frequency phase data quality

The quality of Global Navigation Satellite SystemsGlobal Navigation Satellite Systems Global Navigation Satellite Systems (Global Navigation Satellite Systems Global Navigation Satellite Systems Global Navigation Satellite Systems GNSS) data is one important factor for precise navigation and positioning by using GNSS technique. We proposed a new method to monitor GNSS single-frequency phase data quality by using high-rate epoch-by-epoch phase difference (EEPD). We analyzed the influence of ephemeris, carrier frequency (L1, L2 and L3) and latitude (high latitude, middle latitude and low latitude) on the phase data quality evaluation. It is concluded that the use of broadcast and final orbit has little effect on the phase data quality evaluation with EEPD. The broadcast ephemeris can be used while analyzing GNSS single-frequency data quality in real time. The results obtained by using L1, L2 and L3 observations are almost the same and the GNSS phase quality evaluation can be analyzed by using single-frequency data. The latitudes of stations have a great influence on the quality evaluation of phase data using EEPD. At the same time, Bernese software is used to analyze the feasibility and reliability of EEPD. The results obtained with EEPD are compared with those obtained by Bernese. The results by different methods show good consistency, which shows that EEPD can be reliably used to evaluate the GNSS data quality.&nbsp; &nbsp

The worldwide physical height datum project

The definition of a common global vertical coordinate system is nowadays one of the key points in Geodesy. With the advent of GNSS, a coherent global height has been made available to users. The ellipsoidal height can be obtained with respect to a given geocentric ellipsoid in a fast and precise way using GNSS techniques. On the other hand, the traditional orthometric height is not coherent at global scale. Spirit levelling allows the estimation of height increments so that orthometric heights of surveyed points can be obtained starting from a benchmark of known orthometric heights. As it is well known, this vertical coordinate refers to the geoid, which is assumed to be coincident to the mean sea level. By means of a tide gauge, the mean sea level is estimated and thus a point of known orthometric height is defined. This assumption, which was acceptable in the past, became obsolete given the level of precision which is now required. Based on the altimetry observation, one can precisely quantify the existing discrepancy between geoid and mean sea level that can amount to 1 ÷ 2 m at global scale. Therefore, different tide gauges provide biased estimates of the geoid, given the discrepancy between this equipotential surface and the mean sea level. Also, in the last years, another vertical coordinate was used, the normal height that was introduced in the context of the Molodensky theory. In this paper, a review of the existing different height systems is given and the relationships among them are revised. Furthermore, an approach for unifying normal height referring to different tide gauges is presented and applied to the Italian test case. Finally, a method for defining a physical height system that is globally coherent is discussed in the context of the definition of the International Height Reference System/Frame, a project supported by the Global Geodetic Observing System of the International Association of Geodesy (IAG). This project was established in 2015 during the XXVI IAG General Assembly in Prague as described in IAG Resolution no. 1 that was presented and adopted there.

ON THE COMBINATION OF PSINSAR AND GNSS TECHNIQUES FOR LONG-TERM BRIDGE MONITORING

Abstract. Satellite based monitoring techniques are nowadays an emerging tool for structural health monitoring. In this work, we are interested in the study of the deformations of a cable-stayed bridge using both PsInSAR and GNSS techniques. The content of this paper is mainly dedicated to the development and optimization of GNSS and PsInSAR equipments installed on the bridge. We also present the data processing tools with the aim of providing accurate and reliable measurements that will be used to understand the structure behaviour in medium and long terms. We are dealing also with the uncertainty of PsInSAR measurements points localisation to determine accurately where structural motions occur. Results from GNSS show that the bridge undergoes reversible daily and seasonal displacements in the order of few centimetres. PsInSAR results still not completely clear but reveal some limitations related to PS detection on such structures. Future works need to be made on PS detection improvement to exploit GNSS and PsInSAR conjointly for bridge monitoring.

Tuz Gölü Fay Zonu (TGFZ) Güney Kesimine ait Tektonik Hareketlerin GNSS Gözlemleri ile İzlenmesi

Günümüzde aktif fayların yakın alanlarına kurulan deformasyon ağlarının GNSS tekniği ile izlenmesi sonucunda depreme ait zamanı belirlemek mümkün olmasa da faylar üzerinde biriken gerilmeler yardımıyla muhtemel deprem konumları tahmin edilebilmektedir. Orta Anadolu Neotektonik Bölgesini, Konya-Eskişehir ve Kayseri-Sivas Neotektonik Bölgeleri olmak üzere iki alt neotektonik bölgeye ayıran bir geçiş zonu olan yaklaşık 220 km uzunluğundaki Tuz Gölü Fay Zonu (TGFZ)’nun kırılması durumunda büyüklüğü (M) yaklaşık 6-7 olan bir depreme sebep olabileceği bilinmektedir. Fay zonunun bu potansiyeli dikkate alınarak, bulunduğu alanda meydana gelen deformasyonların hesaplanması amacıyla Tuz Gölü Fay Zonu’nun Güney Kesiminde doğu-batı yönlü profil şeklinde 24 adet nirengi tesisi kurulmuştur. Oluşturulan ağda 2018-2019 yıllarında 3 periyot GNSS ölçüsü yapılmış ve elde edilen sonuçlar GAMIT/GLOBK yazılım takımı ile değerlendirilerek bölgenin güncel hız haritası elde edilmiştir. Yapılan çalışmada, Tuz Gölü Fay Zonu Güney kesiminde Avrasya referans sistemi sabit olmak üzere yıllık 10 ile 35 mm arasında batı ve kuzey batı yönünde bir hareket belirlenmiştir. Noktalara ait standart sapma değerleri 2-6 mm arasında değişmektedir. İlerleyen yıllarda yapılan yeni kampanya ölçüleri ile birlikte standart sapma değerlerinin azalacağı düşünülmektedir.

Crustal movement derived by GNSS technique considering common mode error with MSSA

Common mode errors (CMEs) are a kind of space–time related error. In order to estimate the influence of CMEs on the estimation of station velocity and analyze the crustal movement, GPS data around the world from 2011 to 2016 were precisely processed to obtain precise coordinate time series with one optimal sub-network scheme. The multi-channel singular spectrum analysis (MSSA) and principal component analysis (PCA) are used to extract the CMEs. In order to justify the reliability of extracting CMEs by MSSA, the results of extracting CMEs by PCA are compared. The comparison results show that MSSA can extract CMEs more effectively. The accuracy of the reference frame origin was considered. The trend of GPS site movement determined by MSSA is linearly fitted with the least squares method to estimate the velocity. In order to analyze the influence of CMEs on the estimation of velocity, the velocity is estimated from the coordinate with/without CMEs andtheassociateduncertainties are analyzed. The results indicate that the standard deviation of uncertainty in N, E and U decreased by 11.76%, 4.76% and 28.17%, respectively. The results of IGS stations in the study are compared with the velocity released by the International Terrestrial Reference Frame (ITRF), and the results show that after removing the CMEs by MSSA, the standard deviation of differences in N, E and U decreased by 44.59%, 32.31% and 40.70%, respectively. The velocities before and after removing the CMEs were compared with the ITRF2014 plate motion model, and the results show that the standard deviation of differences in N, E and U decreased by 25.00%, 17.83% and 22.10%, respectively. Finally, a detailed analysis of the global crustal movement is made.

An Improved Method Using SINS/PPP Method for Land Vehicle Gravimetry

Differential GNSS has been successfully applied in the SINS/GNSS vehicle gravity measurement method over the past few decades. However, GNSS error source has the spatio-temporal correlation in the differential mode. The navigation resource utilization efficiency is degraded due to the limitation of the baseline distance and the satellite common view. Using only one satellite receiver with high precision satellite orbit parameters and clock parameters, establishing navigation error models and parameter estimation methods, and obtaining high-precision receiver dynamic positioning, Precise Point Positioning (PPP) is a promising non-differential mode GNSS technique. The advantages of PPP are that it is simple to operate, low in cost, and not limited by the requirements for establishing a base station. This paper presents an SINS/PPP method for land vehicle gravimetry. Based on the strapdown gravimeter SGA-WZ02 developed by the National University of Defense Technology (NUDT), a land vehicle gravimetry test was carried out on a road about 36 kilometres long. The test consists of four measuring lines back and forth in the north-south direction with an average speed of 40km/h. Using this method, the internal accuracy of four repeated lines is 0.52mGal/0.9km. Compared with the results obtained by traditional SINS/GNSS method, the internal accuracy is 0.51mGal/0.9km, which shows that the accuracy calculated by SINS/PPP method is comparable to the results calculated by SINS/DGNSS method. Practical gravimetry results indicate that the proposed SINS/PPP method in this paper can meet the requirements of vehicle gravimetry under ideal GNSS observation conditions, and the feasibility of PPP technology for vehicle gravimetry is verified. Finally, some discussions and suggestions about the applicability of the method and its further improvement are put forward.

Determination of the tram track axis using a multi receiver GNSS measurement system

This article refers to research, that has been conducted by an interdisciplinary research team from the Gdańsk University of Technology and the Maritime University in Gdynia since 2009. These investigation concerns the determination of a railway track axis using the mobile satellite measurement technique. Following the dynamic development of GNSS techniques, that could be seen in the last decade, the team carried out further experiments aimed at developing an effective measurement method. Using the acquired experience in this period, another measurement campaign was carried out on the tram tracks in Gdansk. The main goal of these measurements was to check how the new assumptions regarding the method of mounting the antennas as well as their placement on the measuring platform will work in various field conditions. For this purpose, ten sets of GNSS receivers offered by two independent manufacturers – currently market leaders – were used. The choice of testing track section made it possible to analyze the repeatability of results obtained from multiple measurements in conditions of varying GNSS signal availability. The article presents in a synthetic way the course of this research and the obtained results. Keywords: Tram track; Satellite measurements; Accuracy analysis

UAV Photogrammetry and Ground Surveys as a Mapping Tool for Quickly Monitoring Shoreline and Beach Changes

The aim of this work is to evaluate UAV photogrammetric and GNSS techniques to investigate coastal zone morphological changes due to both natural and anthropogenic factors. Monitoring morphological beach change and coastline evolution trends is necessary to plan efficient maintenance work, sand refill and engineering structures to avoid coastal drift. The test area is located on the Northern Adriatic coast, a few kilometres from Ravenna (Italy). Three multi-temporal UAV surveys were performed using UAVs supported by GCPs, and Post Processed Kinematic (PPK) surveys were carried out to produce three-dimensional models to be used for comparison and validation. The statistical method based on Crossover Error Analysis was used to assess the empirical accuracy of the PPK surveys. GNSS surveys were then adopted to evaluate the accuracy of the 2019 photogrammetric DTMs. A multi-temporal analysis was carried out by gathering LiDAR dataset (2013) provided by the “Ministero dell’Ambiente e della Tutela del Territorio e del Mare” (MATTM), 1:5000 Regional Technical Cartography (CTR, 1998; DBTR 2013), and 1:5000 AGEA orthophotos (2008, 2011). The digitization of shoreline position on multi-temporal orthophotos and maps, together with DTM comparison, permitted historical coastal changes to be highlighted.

Determination of the tectonic plates motion parameters based on SLR, DORIS and VLBI stations positions

Abstract On the base of International Terrestrial Reference Frame 2008 (ITRF2008) a new global plate model of station positions and velocities with accuracy 1–3 mm and 1 mm per year respectively was established. Next, this model was used in our paper for plate motion parameters estimation for the major plates as Eurasian, North American, Pacific and small plates as Australian, African and Antarctic on the base of the observation campaigns for three techniques: Satellite Laser Ranging (SLR), Doppler Orbitography by Radiopositioning Integrated on Satellite system (DORIS) and Very Long Baseline Interferometry (VLBI), each technique was analyzed separately. Investigation for GNSS technique is scheduled to take place in the future. The plate motion parameters were adjusted using least squares method and sequential solution. In the first stage, the plate motion parameters were determined for two selected stations and next stations were added until stability of the solution was observed. Final results of our solution were compared with the APKIM 2005 IGN model by H. Drewes. Agreement of solutions is order 2 degrees or better.

Research on Accurate Positioning-point and Setting-out of Hoisting Operation for Construction Tower Cranes Based on GNSS Techniques

GNSS receiver is one of sensors for accurate-control of tower crane. The low-accuracy of m-level navigation application based on pseudo-range is insatiable the development requirements of intelligent tower crane. In order to improve the positioning accuracy for tower crane based on GNSS techniques, a precise positioning method applied to positioning-point and setting-out via GNSS carrier phase observation is proposed. It is applied to intelligent command for construction tower crane, and a set of GNSS-based positioning-point and setting-out system of hoisting operation system, named as GNSS_PLS, is designed and developed. Finally, the experimental results show that the monitoring accuracy of intelligent command of GNSS_PLS system is cm-level, which verifies the effectiveness of the proposed algorithm in this paper.

Analysis of Accuracy of the Generous Orthophotomap on the Basis of Digital Aerial Photos Collected for the Airport Dęblin

Abstract The article presents the technological process of generating an orthophotomap based on photos obtained from the aviation ceiling. To achieve the intended goal, it was necessary to design and measure a field photogrammetric matrix. A method of GNSS technique measurement was chosen for the measurement of the photopoints. The aim of the research was to generate an orthophotomap and to evaluate the impact of parameter selection on the orthophotomap accuracy. The obtained ortho-images were compared with the orthophotomap obtained from the resources of the Central Geodesic and Cartographic Documentation Center. Based on the obtained results, it was found that the change of parameters during the generation of intermediate products does not significantly affect the accuracy of the resulting orthophotomap.