Real Time Kinematic Mode Research Articles

Accuracy analysis of UAV aerial photogrammetry based on RTK mode, flight altitude, and number of GCPs

Abstract The optimization of an unmanned aerial vehicle (UAV) aerial photogrammetry scheme is crucial for achieving higher precision mapping results. Three representative factors, namely the real-time kinematic (RTK) mode, flight altitude, and the number of ground control points (GCPs) were selected to analyze their impact on UAV aerial photogrammetry accuracy. Four flight altitude tests were conducted separately in two RTK modes, and five GCP layout schemes were designed. Based on this, the root mean square error (RMSE) values of 40 aerial photogrammetric results were analyzed. The results showed a significant correlation between flight altitude and resolution of the UAV aerial photogrammetric results. Further, conversion formulas between actual image resolution and flight altitude for different GCP values were also derived in RTK and non-RTK modes. In the case of precise positioning, the horizontal and vertical accuracy of the aerial photogrammetric image decreased with increasing flight altitude. Under the same flight altitude, the addition or no addition of GCPs, including changes in GCP numbers, had no significant effect on improving the accuracy of aerial photogrammetry in RTK mode. However, in non-RTK mode, the number of GCPs significantly affected accuracy. The horizontal and vertical RMSE values decreased rapidly with the increase in GCP numbers and then stabilized. However, regardless of whether RTK was activated, an excessive number of GCPs was not conducive to improving the accuracy of aerial photogrammetric results. The mapping accuracy of UAVs in RTK mode without GCPs was equivalent to that in non-RTK mode with GCPs. Therefore, when using RTK-UAVs, deploying GCPs is unnecessary under suitable circumstances. Finally, practical suggestions for optimizing the UAV aerial photogrammetry scheme are provided as a reference for related applications.

Testing and Analysis of Selected Navigation Parameters of the GNSS/INS System for USV Path Localization during Inland Hydrographic Surveys.

One of the main methods of the path localization of moving objects is positioning using Global Navigation Satellite Systems (GNSSs) in cooperation with Inertial Navigation Systems (INSs). Its basic task is to provide high availability, in particular in areas with limited access to satellite signals such as forests, tunnels or urban areas. The aim of the article is to carry out the testing and analysis of selected navigation parameters (3D position coordinates (Northing, Easting, and height) and Euler angles (pitch and roll)) of the GNSS/INS system for Unmanned Surface Vehicle (USV) path localization during inland hydrographic surveys. The research used the Ellipse-D GNSS/INS system working in the Real Time Kinematic (RTK) mode in order to determine the position of the "HydroDron" Autonomous Surface Vehicle (ASV). Measurements were conducted on four representative routes with a parallel and spiral arrangement of sounding profiles on Lake Kłodno (Poland). Based on the obtained research results, position accuracy measures of the "HydroDron" USV were determined using the Ellipse-D GNSS/INS system. Additionally, it was determined whether USV path localization using a GNSS/INS system working in the RTK mode meets the positioning requirements for inland hydrographic surveys. Research has shown that the Ellipse-D system operating in the RTK mode can be successfully used to position vessels when carrying out inland hydrographic surveys in all International Hydrographic Organization (IHO) Orders (Exclusive, Special, 1a/1b and 2) even when it does not work 100% correctly, e.g., loss of RTK corrections for an extended period of time. In an area with limited coverage of the mobile network operator (30-40% of the time the receiver operated in the differential mode), the positioning accuracy of the "HydroDron" USV using the Ellipse-D GNSS/INS system working in the RTK mode was from 0.877 m to 0.941 m for the R95(2D) measure, depending on the route travelled. Moreover, research has shown that if the Ellipse-D system performed GNSS/INS measurements using the RTK method, the pitch and roll error values amounted to approx. 0.06°, which is almost identical to that recommended by the device manufacturer. However, when working in the differential mode, the pitch and roll error values increased from 0.06° to just over 0.2°.

Multi-Sensor and Analytical Constraints Tightly Augmented BDS-3 RTK for Vehicle-Borne Positioning

The third generation BeiDou Navigation Satellite System (BDS-3) can provide high-accuracy service for vehicle-borne positioning and navigation. The performance of BDS-3 in terms of accuracy, continuity, and reliability, however, are significantly degraded in environments with weak satellite observability. To improve the positioning performance of BDS-3 around the partial and complete signal-blocked areas, this paper presents a multi-sensor and analytical constraints tightly augmented BDS-3 Real-time Kinematic (RTK). The Non-holonomic Constraint (NHC), vehicle-odometer, and dual-antenna-based attitude constraints applied to restrain the drift of the position estimate from Inertial Measurement Units (IMU). Compared to previous work, it’s the first time to reveal that the Ambiguity Resolution (AR) performance of RTK can be augmented by integrating these measurements. To validate the performance of this proposed method, the drifts of position and attitude during the poor satellite observability and the impacts of those sensors and constraints on ambiguity fixing are analyzed based on an urban vehicle-borne test. The test results illustrate that the presented model brought 52.73%, 55.56%, and 49.44% positioning accuracy improvements in the north, east, and vertical components compared to the RTK mode. Meanwhile, 10.87% and 57.20% attitude accuracy enhancements in roll and heading were obtained compared to the traditional RTK/IMU tight integration mode. In addition, this presented model can retain the accuracy of position and attitude during the partial and complete satellite signal outage periods, and can also improve the ambiguity resolution performance significantly.

Tightly Coupled Integration of BDS-3 B2b RTK, IMU, Odometer, and Dual-Antenna Attitude

Real Time Kinematic (RTK) based on single-frequency observation is still widely used in many fields due to the characteristics of low-cost and low-power consumption. However, the positioning performance of single-frequency RTK in terms of accuracy, stability, and continuity would be significantly degraded during the harsh satellite environments. To improve the performance, this contribution presented a model of multi-sensor and analytical observations augmented the single frequency RTK tightly based on a modified Psi-angle state model. In such a model, the single frequency observations of the new signal of BDS-3 B2b are tightly integrated with inertial measurements, odometer data, dual-antenna attitude, and non-holonomic constraint. To evaluate the presented model, the typical navigation performance and the ambiguity resolution performance are analyzed based on a set of vehicle-borne data. Results illustrated that the Inertial Navigation System (INS) would bring about 13.5%, 16.2%, and 12.3% position enhancements to the BDS-3 B2b RTK mode. Such improvements could be up to 15.9%, 16.2%, and 25.2% while adding the non-holonomic constraint and odometer data. Besides, non-holonomic constraint and odometer also upgrade the attitude accuracy visibly in pitch and heading directions, with enhancements of about 16.9% and 62.9%. In contrast, augmentations from the dual-antenna attitude are mainly presented in terms of heading angle with about 29.5% compared to the RTK/INS/Odometer/NHC tight integration mode. Besides, the convergence time of yaw angle is visibly enhanced while using the odometer/NHC, the dual-antenna heading, or the two together. Moreover, the ambiguity resolution performance could also be improved while using the presented model. Due to the enhancements in position and attitude brought by different sensors, the ADOP performance would be improved to varying degrees. Besides, the fixed rate and reliability of ambiguity resolution could also be enhanced.

Production of orthophoto map using mobile photogrammetry and comparative assessment of cost and accuracy with satellite imagery for corridor mapping: a case study in Manesar, Haryana, India

ABSTRACT The study aims to find a low-cost alternate technology to get imagery, using mobile platform, and produce digital orthophoto for corridor mapping, with a higher degree of accuracy and which can reduce the lag time of acquisition of data. The present study uses digital single-lens reflex cameras, mounted on a mobile vehicle, and acquisition of data in the video format rather than still photographs, as traditionally used in mobile mapping systems. The videos are used to create a set of images and orthophotos. A widespread ground control points were recorded in the study area, using the global navigation satellite system receiver, which measured the control points in real-time kinematic mode. Generation of digital orthophoto has been completed using the captured mobile imagery and ground control point. Furthermore, procurement of satellite imagery and aerial triangulation using ground control points have been done. While comparing the planimetric accuracy of orthophoto against satellite imagery using the ground control points, the achieved root mean square error value of produced orthophoto is 0.171 m in X axis and 0.205 m in Y axis. However, for Cartosat -1 satellite imagery, the RMSE value for X is 1.22 m and for Y is 1.98 m. This research proposes the alternate low-cost mobile mapping method to capture the imagery for orthophoto production. The cost of orthophoto production from mobile image was found 77% cheaper than the orthophoto cost from fresh/latest satellite imagery procurement, while the overall production was 70% cost-effective than the orthophoto maps made from archived imagery.

Evaluation of Positioning Accuracy of Smartphones under Different Canopy Openness

This study focuses on evaluating the positioning accuracy of smartphones in a deciduous forest environment compared to various levels of Global Navigation Satellite System (GNSS) devices. In a mixed coniferous forest with 90% broad-leaved forest (deciduous season), the accuracy of 57 test points was evaluated according to different openness levels under the forest. Taking the coordinates obtained by survey-grade GNSS devices in RTK (Real-time Kinematic) mode as standard, the accuracy of the single-point positioning (SPP) mode and precise-point positioning (PPP) mode obtained by three smartphones (one single frequency and two dual frequency), one survey-grade receiver and one recreational-grade receiver are compared. It can be found that there was a significant positive correlation between canopy openness and carrier-to-noise density(C/N0) (p < 0.05). Meanwhile, the C/N0 of survey-grade devices is significantly higher than that of smartphones. The results show that the positioning accuracy of dual-frequency smartphones under forests is better than that of single-frequency smartphones. Furthermore, the positioning accuracy of the smartphone corrected by PPP mode is better than that of the recreational-grade GNSS receiver and can achieve an accuracy of about 2.5 m in the horizontal direction, which can be used for forestry stakeout, reset and determination of forest area boundaries in environments with high openness (R > 0.7). However, in an environment with low openness (R < 0.7) and relatively complex forest area positioning, survey-grade GNSS devices are still required to cooperate with the PPP or real-time differential positioning method to obtain accurate sub-meter-level positioning data.

Light and Shadow in Mapping Alpine Snowpack With Unmanned Aerial Vehicles in the Absence of Ground Control Points

AbstractRecent developments in unmanned aerial vehicles (UAV) and structure from motion (SfM) algorithms have shown reliable results for retrieving snow depth distribution. However, their ability to obtain accurate results usually relies on deploying and measuring the exact position of ground control points (GCP) for georeferencing the information. Commercial UAVs can now provide real time kinematic (RTK) positioning of the images with centimetric accuracy. Nonetheless, their operational applicability for observing snow distribution in highly heterogeneous mountain areas has not been evaluated. This study presents a complete assessment of the reliability of snow depth observations from a fixed‐wing UAV working in RTK mode with an RGB camera. During the 2018–2019 season, seven field campaigns (13 UAV flights) were undertaken covering 0.48 km2 in complex alpine terrain in the Pyrenees. The UAV observations obtained under different light conditions and flight block configurations (altitude and image overlaps) in the same day were evaluated with terrestrial laser scanner acquisitions. Two SfM processing options of the UAV images were also compared. When the study area received direct solar light, the results were comparable to previous studies that had used GCPs, with an average root mean squared error of 0.19 m and an average absolute snow volume discrepancy lower than 4%. However, when large areas were under shadow from the terrain, or solar light was affected by clouds, the estimated error tripled. The quality of the snow depth maps was little affected by the snow covered area and the flight mission configurations.

The possibility of Using the Low-Cost External Antenna with Smartphone for Accurate Surveying Applications by RTX Technology

Real Time Extended (RTX) technology works to take advantage of real-time data comes from the global network of tracking stations together with inventor locating and compression algorithms to calculate and relaying the orbit of satellite, satellite atomic clock, and any other systems corrections to the receivers, which lead to real-time correction with high accuracy. These corrections will be transferred to the receiver antenna by satellite (where coverage is available) and by IP (Internet Protocol) for the rest of world to provide the accurate location on the screen of smartphone or tablet by using specific software. The purpose of this study was to assess the accuracy of Global Navigation Satellite System (GNSS) low-cost external antenna and possibility for using it with a smartphone to measure the points in Real Time Kinematic (RTK) and (RTX) modes, obtaining the same accuracy by using high-cost (GNSS) receiver with same modes. The assessment has applied through comparing the control points measured in static mode (3 to 5 hours) and corrected by Online Positioning User Service (OPUS) web-based processing software with same control points measured in RTX mode by GNSS low-cost external antenna (5 minutes). The results of an assessment were obtained horizontal and vertical location error in real time, by receiver getting the RTX correction data over the satellite link were RMS (east 41cm, north 35 cm, elevation 94 cm), that means it’s more suitable for automotive, agriculture, and forestry application, As for the RTK mode, the comparison of the differences in RTK mode between the two antennas were RMS (north 5 cm, east 6 cm, elevation 10). This result indicates that the GNSS low-cost external antenna might be very useful in accurate surveying application.

Coastal Mapping Using DJI Phantom 4 RTK in Post-Processing Kinematic Mode

Topographic and geomorphological surveys of coastal areas usually require the aerial mapping of long and narrow sections of littoral. The georeferencing of photogrammetric models is generally based on the signalization and survey of Ground Control Points (GCPs), which are very time-consuming tasks. Direct georeferencing with high camera location accuracy due to on-board multi-frequency GNSS receivers can limit the need for GCPs. Recently, DJI has made available the Phantom 4 Real-Time Kinematic (RTK) (DJI-P4RTK), which combines the versatility and the ease of use of previous DJI Phantom models with the advantages of a multi-frequency on-board GNSS receiver. In this paper, we investigated the accuracy of both photogrammetric models and Digital Terrain Models (DTMs) generated in Agisoft Metashape from two different image datasets (nadiral and oblique) acquired by a DJI-P4RTK. Camera locations were computed with the Post-Processing Kinematic (PPK) of the Receiver Independent Exchange Format (RINEX) file recorded by the aircraft during flight missions. A Continuously Operating Reference Station (CORS) located at a 15 km distance from the site was used for this task. The results highlighted that the oblique dataset produced very similar results, with GCPs (3D RMSE = 0.025 m) and without (3D RMSE = 0.028 m), while the nadiral dataset was affected more by the position and number of the GCPs (3D RMSE from 0.034 to 0.075 m). The introduction of a few oblique images into the nadiral dataset without any GCP improved the vertical accuracy of the model (Up RMSE from 0.052 to 0.025 m) and can represent a solution to speed up the image acquisition of nadiral datasets for PPK with the DJI-P4RTK and no GCPs. Moreover, the results of this research are compared to those obtained in RTK mode for the same datasets. The novelty of this research is the combination of a multitude of aspects regarding the DJI Phantom 4 RTK aircraft and the subsequent data processing strategies for assessing the quality of photogrammetric models, DTMs, and cross-section profiles.

ОЦЕНКА ТОЧНОСТИ ОПРЕДЕЛЕНИЯ КООРДИНАТ СПУТНИКОВЫМИ ПРИЕМНИКАМИ ЕFT M3 GNSS И EFT M4 GNSS В РЕЖИМЕ RTK

The paper presents the test results of satellite receivers EFT M3 GNSS and EFT M4 GNSS in Real Time Kinematic (RTK) mode. At ten points near the NSKW permanent operating base station, measurements were made in the RTK mode by the tested receivers and in the "static" mode by the Trimble 5700 receiver. In addition, the normal heights of points from leveling of class II with the N-05 level were determined. The points are removed from the base station at distances from 39 m to 1227 m. The accuracy was estimated by the differences of double non-equal measurements in the RTK and "static" modes. For additional control of the accuracy estimation in determining the heights, differences of normal and geodetic heights are used. The work shows that the mean square error of measurements in the RTK mode does not exceed 16 mm in plan and height. In RTK mode, modern GNSS receivers EFT M3 GNSS and EFT M4 GNSS can achieve a centimeter level of accuracy in determining the spatial coordinates of points. The errors of the tested receivers in RTK mode are comparable.

Accurate Three Dimensional Coordinates Measurements Using Differential GPS Real Time Kinematic Mode

The accurate 3-D coordinate's measurements of the global positioning systems are essential in many fields and applications. The GPS has numerous applications such as: Frequency Counters, Geographic Information Systems, Intelligent Vehicle Highway Systems, Car Navigation Systems, Emergency Systems, Aviations, Astronomical Pointing Control, and Atmospheric Sounding using GPS signals, tracking of wild animals, GPS Aid for the Blind, Recorded Position Information, Airborne Gravimetry and other uses. In this paper, the RTK DGPS mode has been used to create precise 3-D coordinates values for four rover stations in Baghdad university camp. The HiPer-II Receiver of global positioning system was used to navigate the coordinate value. The results will be compare with the Google Earth viewer coordinates values, the comparison shows that absolute error was few millimeters between actual and measured coordinate's values.

Quality Assessment of DSMs Produced from UAV Flights Georeferenced with On-Board RTK Positioning

High-resolution Digital Surface Models (DSMs) from unmanned aerial vehicles (UAVs) imagery with accuracy better than 10 cm open new possibilities in geosciences and engineering. The accuracy of such DSMs depends on the number and distribution of ground control points (GCPs). Placing and measuring GCPs are often the most time-consuming on-site tasks in a UAV project. Safety or accessibility concerns may impede their proper placement, so either costlier techniques must be used, or a less accurate DSM is obtained. Photogrammetric blocks flown by drones with on-board receivers capable of RTK (real-time kinematic) positioning do not need GCPs, as camera stations at exposure time can be determined with cm-level accuracy, and used to georeference the block and control its deformations. This paper presents an experimental investigation on the repeatability of DSM generation from several blocks acquired with a RTK-enabled drone, where differential corrections were sent from a local master station or a network of Continuously Operating Reference Stations (CORS). Four different flights for each RTK mode were executed over a test field, according to the same flight plan. DSM generation was performed with three block control configurations: GCP only, camera stations only, and with camera stations and one GCP. The results show that irrespective of the RTK mode, the first and third configurations provide the best DSM inner consistency. The average range of the elevation discrepancies among the DSMs in such cases is about 6 cm (2.5 GSD, ground sampling density) for a 10-cm resolution DSM. Using camera stations only, the average range is almost twice as large (4.7 GSD). The average DSM accuracy, which was verified on checkpoints, turned out to be about 2.1 GSD with the first and third configurations, and 3.7 GSD with camera stations only.

Evaluation on real-time dynamic performance of BDS in PPP, RTK, and INS tightly aided modes

Since China’s BeiDou satellite navigation system (BDS) began to provide regional navigation service for Asia-Pacific region after 2012, more new generation BDS satellites have been launched to further expand BDS’s coverage to be global. In this contribution, precise positioning models based on BDS and the corresponding mathematical algorithms are presented in detail. Then, an evaluation on BDS’s real-time dynamic positioning and navigation performance is presented in Precise Point Positioning (PPP), Real-time Kinematic (RTK), Inertial Navigation System (INS) tightly aided PPP and RTK modes by processing a set of land-borne vehicle experiment data. Results indicate that BDS positioning Root Mean Square (RMS) in north, east, and vertical components are 2.0, 2.7, and 7.6 cm in RTK mode and 7.8, 14.7, and 24.8 cm in PPP mode, which are close to GPS positioning accuracy. Meanwhile, with the help of INS, about 38.8%, 67.5%, and 66.5% improvements can be obtained by using PPP/INS tight-integration mode. Such enhancements in RTK/INS tight-integration mode are 14.1%, 34.0%, and 41.9%. Moreover, the accuracy of velocimetry and attitude determination can be improved to be better than 1 cm/s and 0.1°, respectively. Besides, the continuity and reliability of BDS in both PPP and RTK modes can also be ameliorated significantly by INS during satellite signal missing periods.

Localization Based on Magnetic Markers for an All-Wheel Steering Vehicle.

Real-time continuous localization is a key technology in the development of intelligent transportation systems. In these systems, it is very important to have accurate information about the position and heading angle of the vehicle at all times. The most widely implemented methods for positioning are the global positioning system (GPS), vision-based system, and magnetic marker system. Among these methods, the magnetic marker system is less vulnerable to indoor and outdoor environment conditions; moreover, it requires minimal maintenance expenses. In this paper, we present a position estimation scheme based on magnetic markers and odometry sensors for an all-wheel-steering vehicle. The heading angle of the vehicle is determined by using the position coordinates of the last two detected magnetic markers and odometer data. The instant position and heading angle of the vehicle are integrated with an extended Kalman filter to estimate the continuous position. GPS data with the real-time kinematics mode was obtained to evaluate the performance of the proposed position estimation system. The test results show that the performance of the proposed localization algorithm is accurate (mean error: 3 cm; max error: 9 cm) and reliable under unexpected missing markers or incorrect markers.

3D Subsoil Model of the San Biagio ‘Salinelle’ Mud Volcanoes (Belpasso, Sicily) derived from Geophysical Surveys

Mud volcanoes are common in active mountain fronts. At Mt. Etna, located just between the Apennine front in Sicily and its foredeep, there are some manifestations of mud volcanism in the lower border of the volcanic edifice. The activity of these mud volcanoes is characterized by persistent emission of muddy water mixed with salts, which rises to the surface due to the gas pressure in the subsoil. The San Biagio Salinelle is one of the three mud volcano fields located around the Paterno eruptive monogenic apparatus; this old volcanic structure was one of the first subaerial volcanic manifestations that formed in the pre-Etnean phase. It is not fully clear whether and how the activity of the mud fields is connected with the volcanic activity of Mt. Etna. Noninvasive geophysical surveys were carried out in the area of the active cone of the San Biagio Salinelle, in order to identify the probable ascent path of the emitted products. Seismic ambient noise records were collected at the nodes of a specially designed grid and, subsequently, the V s values were obtained from an active seismic survey. A digital elevation model (DEM) of the area was obtained by a topographic survey, carried out with the GNSS technique (global navigation satellite system), in real-time kinematic mode. The DEM and the topographic benchmark installed will represent the reference surface for future periodic monitoring of the ongoing deformation in the area. Our results provide an accurate and detailed 3D subsurface model showing the shallower feeding system of the investigated mud volcano.

Kinematic Models for Odometry of a Six-Wheeled Mobile Robot

Abstract: Paper describes kinematic models of a mobile robot with a six-wheeled chassis. These models can be used for estimation of its position and orientation using an odometry method. Basic model, advanced model, and model based on polynomial replacements are introduced. Steps of model identification are discussed. Described models are applied on data from a real mobile robot and there is evaluated position and azimuth error of odometry solution. Global navigation satellite systems in real time kinematic mode were used as a reference positioning system for evaluation of accuracy of odometry solution.

Precision Analysis of Trimble Rtx Surveying Technology with Xfill Function in the Context of Obtained Conversion Observations

Abstract As a result of traditional geodetic surveying we usually achieve observations which are then used for calculating rectangular coordinates onto a plane along with precision evaluation. In this article the surveying methods are presented in which the situation is different. Test measurements were carried out, consisting in the measurement of a fragment of detailed control network in RTK (Real Time Kinematic) and RTX (Real Time Extended) mode with xFill function. First, the rectangular coordinates onto a plane (through the transformation of data ellipsoidal) were obtained, on the basis of which the conversion observations were determined and they were compared with each other, as well as with reference parameters - conversion observations out of detailed control network adjustment with use of the method of least squares. The results of the study allow to verify the precision and application possibilities of conversion observations obtained thanks to Trimble RTX technology with xFill function. Application of this surveying method in typical geodetic tasks is fully justifiable. Nevertheless, it is recommendable to be aware of the correlations of absolute or relative values obtained in RTX procedure to reference parameters, which in turn will enable conclusive verification of the possibilities of Trimble RTX technology application in certain geodetic surveys.

Precise Point Positioning Using the Regional BeiDou Navigation Satellite Constellation

On 27 December 2012 it was announced officially that the Chinese Navigation Satellite System BeiDou (BDS) was able to provide operational services over the Asia-Pacific region. The quality of BDS observations was confirmed as comparable with those of GPS, and relative positioning in static and kinematic modes were also demonstrated to be very promising. As Precise Point Positioning (PPP) technology is widely recognized as a method of precise positioning service, especially in real-time, in this contribution we concentrate on the PPP performance using BDS data only. BDS PPP in static, kinematic and simulated real-time kinematic mode is carried out for a regional network with six stations equipped with GPS- and BDS-capable receivers, using precise satellite orbits and clocks estimated from a global BDS tracking network. To validate the derived positions and trajectories, they are compared to the daily PPP solution using GPS data. The assessment confirms that the performance of BDS PPP is very comparable with GPS in terms of both convergence time and accuracy.

Visual monitoring method on fresh concrete vibration

An integrated visual monitoring system to determine trajectory and duration on each vibrating motion of vibrator during concrete placed on construction site was introduced, which could graphically display vibrating status of fresh concrete. Defects on concrete placing process such as missed vibration, insufficient vibration, or excess vibration could be quantifiably assessed, and therefore, precise and suitable remedy could be offered timely. The system consisted of four functional parts, namely, vibrating trajectory spatial coordinate collected subsystem, vibrating duration-collected subsystem, data process subsystem, and real-time display and assesses subsystem of vibrating status. The principle of operation was explained in this article. Firstly, accurate signals combined spatial coordinates were achieved by dual-satellite systems, e.g., GPS (Global Position System) and GLONASS (Global Navigation Satellite System), with RTK (Real Time Kinematics) mode and, duration of each vibration from start to end was determined by electrode device, respectively. Secondly, the wireless signals were sent to the terminal computer via MCC (Mono-Chip Computer) integrated. Finally, the worked status of vibrator on terminal was displayed simultaneously supported by assessment programm on compacting concrete. Tests results from outdoor and application in-situ proved that the system could monitor the vibration process in real-time reliably and quantifiably while fresh concrete was placed, and an innovative informationaized method might be realized.

A high spatio-temporal methodology for monitoring dunes morphology based on precise GPS-NRTK profiles: Test-case of Dune of Mónsul on the south-east Spanish coastline

Abstract The effects of erosion and accretion of sand dune systems are often underestimated due to the coarse spatial and temporal resolution data set. This paper shows a specific methodology to monitor, at local scale and high repeatability, the crescentic dune of Monsul in Almeria (SE Spain). Precise spatial information based on high resolution profiles has been obtained periodically by repeated GPS surveys. The dune morphology and associated changes due to erosion and accretion are investigated using the GPS methodology in RTK (Real Time Kinematic) mode. This technique introduces significant improvements compared to other techniques for monitoring small areas such as better repeatability, accuracy, reliability, etc. The availability of the Andalusian Positioning Network, an active network over the region, allowed us to monitor the dune throughout GPS profiles capturing its evolution for the period of April–September, 2010. Three GPS campaigns spaced over time were performed. The framework is established by the active network, avoiding the placement of a local control network in this protected area. The main objective of this study is to perform a control methodology based on NRTK (network RTK) positioning supported by a regional active network, with special emphasis on checking and filtering the surveyed data. The numerical and graphical results presented show a balance between the values of erosion and accretion of sand on the dune.