GNSS RTK Research Articles

Combining UAS LiDAR, Sonar, and Radar Altimetry for River Hydraulic Characterization

Accurate river hydraulic characterization is fundamental to assess flood risk, parametrize flood forecasting models, and develop river maintenance workflows. River hydraulic roughness and riverbed/floodplain geometry are the main factors controlling inundation extent and water levels. However, gauging stations providing hydrometric observations are declining worldwide, and they provide point measurements only. To describe hydraulic processes, spatially distributed data are required. In situ surveys are costly and time-consuming, and they are sometimes limited by local accessibility conditions. Satellite earth observation (EO) techniques can be used to measure spatially distributed hydrometric variables, reducing the time and cost of traditional surveys. Satellite EO provides high temporal and spatial frequency, but it can only measure large rivers (wider than ca. 50 m) and only provides water surface elevation (WSE), water surface slope (WSS), and surface water width data. UAS hydrometry can provide WSE, WSS, water surface velocity and riverbed geometry at a high spatial resolution, making it suitable for rivers of all sizes. The use of UAS hydrometry can enhance river management, with cost-effective surveys offering large coverage and high-resolution data, which are fundamental in flood risk assessment, especially in areas that difficult to access. In this study, we proposed a combination of UAS hydrometry techniques to fully characterize the hydraulic parameters of a river. The land elevation adjacent to the river channel was measured with LiDAR, the riverbed elevation was measured with a sonar payload, and the WSE was measured with a UAS radar altimetry payload. The survey provided 57 river cross-sections with riverbed elevation, and 8 km of WSE and land elevation and took around 2 days of survey work in the field. Simulated WSE values were compared to radar altimetry observations to fit hydraulic roughness, which cannot be directly observed. The riverbed elevation cross-sections have an average error of 32 cm relative to RTK GNSS ground-truth measurements. This error was a consequence of the dense vegetation on land that prevents the LiDAR signal from reaching the ground and underwater vegetation, which has an impact on the quality of the sonar measurements and could be mitigated by performing surveys during winter, when submerged vegetation is less prevalent. Despite the error of the riverbed elevation cross-sections, the hydraulic model gave good estimates of the WSE, with an RMSE below 3 cm. The estimated roughness is also in good agreement with the values measured at a gauging station, with a Gauckler–Manning–Strickler coefficient of M = 16–17 m1/3/s. Hydraulic modeling results demonstrate that both bathymetry and roughness measurements are necessary to obtain a unique and robust hydraulic characterization of the river.

Accuracy analysis of photogrammetric and GNSS RTK based land parcels mapping and measurement on area with dense vegetation and varied topography

Abstract To accelerate the land registration process, Ministry of ATR/BPN of Indonesia instructed to use the photogrammetric method in the Pendaftaran Tanah Sistematis Lengkap (PTSL) started in 2023, stated in the PTSL technical instructions (JUKNIS) 2023 and 2024. Mapping of land parcels on PTSL carried out by digitizing orthophoto by community participation with additional measurements of land parcels that cannot be identified on orthophoto using GNSS RTK, which is an efficient measurement method that can measures high quantity coordinates within centimeter accuracy in a short duration. Banjarnegara Land Office, an office under ATR/BPN which in 2023 carried out PTSL project in accordance with JUKNIS, on the Kemiri and Karangmangu villages, Sigaluh District. The villages located next to each other, have varied topographic with tall and dense vegetation which can greatly influences the process and accuracy of land parcels mapping with photogrammetric method and measurements using the RTK method. In this research, an analysis will be carried out to determine the accuracy suitability of land parcel mapping and measurement based on JUKNIS in the area with varied topography and dense vegetation. This research shows that the mapping and measurement of land parcels as per JUKNIS and other regulations is satisfactory. The orthophoto map’s CE90 and LE90 accuracy is 0.281 meters and 0.673 meters, respectively, with the accuracy variability influenced by GCP coordinates quality and geometry. All digitized land parcel samples achieved planimetric accuracy standards (100%). And the RTK usage still suitable with 98.756% points that met the tolerance, but the accuracy is still affected with vegetation.

Innovative and Cost‐Effective Approaches to the Measurement of Sediment Levels in Small Water Reservoirs

ABSTRACTSedimentation in small water reservoirs poses a critical challenge with significant environmental, economic, and social implications. To address this issue, this study will employ three measurement techniques—GNSS RTK Trimble R8s, Echolot HDS LIVE 7 with Active Imaging 3‐in‐1, and the Mivardi Carp Scout bait boat—to assess sediment levels in Žebětínský Pond in Brno, Czech Republic. The research reveals that each method offers distinct advantages and limitations. Through measurement and triangulated networks, the study creates a digital terrain model that facilitates the determination of reservoir volume and sediment levels. The comparison shows that the cost‐effective alternatives, Echolot HDS LIVE 7 and Mivardi Carp Scout, provide sufficiently accurate results. The evaluation shows that while the GNSS RTK Trimble R8s has the highest level of accuracy and is unique in its ability to measure both along the shoreline of the reservoir and the hard bottom, it comes with increased costs and logistical challenges. The Echolot HDS LIVE 7 and Mivardi Carp Scout offer efficient, cost‐effective solutions that are suitable for a quick estimate of sediment thickness. This research contributes to the use of reliable mathematical models and water management strategies, advocating for a pragmatic approach to the selection of methods based on the project characteristics. The study provides valuable insights into sediment measurement techniques, guiding future endeavors in reservoir management and environmental conservation. It is also used to easily indicate the loss of arable land in the catchment upstream of the reservoir.

4Seasons: Benchmarking Visual SLAM and Long-Term Localization for Autonomous Driving in Challenging Conditions

AbstractIn this paper, we present a novel visual SLAM and long-term localization benchmark for autonomous driving in challenging conditions based on the large-scale 4Seasons dataset. The proposed benchmark provides drastic appearance variations caused by seasonal changes and diverse weather and illumination conditions. While significant progress has been made in advancing visual SLAM on small-scale datasets with similar conditions, there is still a lack of unified benchmarks representative of real-world scenarios for autonomous driving. We introduce a new unified benchmark for jointly evaluating visual odometry, global place recognition, and map-based visual localization performance which is crucial to successfully enable autonomous driving in any condition. The data has been collected for more than one year, resulting in more than 300 km of recordings in nine different environments ranging from a multi-level parking garage to urban (including tunnels) to countryside and highway. We provide globally consistent reference poses with up to centimeter-level accuracy obtained from the fusion of direct stereo-inertial odometry with RTK GNSS. We evaluate the performance of several state-of-the-art visual odometry and visual localization baseline approaches on the benchmark and analyze their properties. The experimental results provide new insights into current approaches and show promising potential for future research. Our benchmark and evaluation protocols will be available at https://go.vision.in.tum.de/4seasons.

Estimation of Surface Water Level in Coal Mining Subsidence Area with GNSS RTK and GNSS-IR

Ground subsidence caused by underground coalmining result in the formation of ponding water on the ground surface. Monitoring the surface water level is crucial for studying the hydrologic cycle in mining areas. In this paper, we propose a combined technique using Global Navigation Satellite System Real-Time Kinematic (GNSS RTK) and GNSS Interferometric Reflectometry (GNSS-IR) to estimate the surface water level in areas of ground subsidence caused by underground coal mining. GNSS RTK is used to measure the geodetic height of the GNSS antenna, which is then converted into the normal height using the local height anomaly model. GNSS-IR is employed to estimate the height from the water surface to the GNSS antenna (or, the reflector height). To enhance the accuracy of the reflector height estimation, a weighted average model has been developed. This model is based on the coefficient of determination of the signal fitted by the Lomb-Scargle spectrogram and can be utilized to combine the reflector height estimations derived from multiple GNSS system and band reflection signals. By subtracting the GNSS-IR reflector height from the GNSS RTK-based normal height, the proposed method-based surface water level estimation can be obtained. In an experimental campaign, a low-cost GNSS receiver was utilized for the collection of dual-frequency observations over a period of 60 days. The collected GNSS observations were used to test the method presented in this paper. The experimental campaign demonstrates a good agreement between the surface water level estimations derived from the method presented in this paper and the reference observations.

THE USE OF UNMANNED AIRCRAFT IN THE PRODUCTION PROCESS OF DRILLING AND BLASTING AT SURFACE MINES

Surface mines that have solid rocks in their geological structure require considerable dedication to the work processes of drilling and blasting. Drilling and blasting, as one of the first work processes in surface mines - quarries, affects all subsequent work processes (loading, transport and crushing) as a result. By improving the effects of drilling and blasting, KPI results are significantly improved on all subsequent work processes, as well as on the reduced impact of mining on the environment. The paper shows the use of UAVs (unmanned aerial vehicles) for the purpose of optimizing the results of drilling and blasting in the Anhovo quarry (carbonate mineral - R. Slovenia), whose entire annual production of 1.5×106 t goes to the cement industry (Alpacem cement d.d. Slovenia). The equipment used in the aforementioned quarry is a handheld Leica GNSS RTK device, a DJI Mavic 3E drone with RTK positioning, a Sandvik Ranger DX800i drilling rig with RTK positioning, as well as BlastMetrix software for processing data obtained from drone images and projecting minefields.

The integration of GNSS RTK and IMU with extended particle filter

The integration of GNSS RTK and IMU with extended particle filter

Design and Development of an Automatic Layout Algorithm for Laser GNSS RTK.

At the current stage, the automation level of GNSS RTK equipment is low, and manual operation leads to decreased accuracy and efficiency in setting out. To address these issues, this paper has designed an algorithm for automatic setting out that resolves the common problem of reduced accuracy in conventional RTK. First, the calculation of the laser rotation center is conducted using relevant parameters to calibrate the instrument's posture and angle. Then, by analyzing the posture information, the relative position and direction of the instrument to the point to be set out are determined, and the rotation angles in the horizontal and vertical directions are calculated. Following this, the data results are analyzed, and the obtained rotation angles are output to achieve automatic control of the instrument. Finally, a rotating laser composed of servo motors and laser modules is used to control the GNSS RTK equipment to locate the set-out point, thereby determining its position on the ground and displaying it in real-time. Compared to traditional GNSS RTK equipment, the proposed automatic setting out algorithm and the developed GNSS laser RTK equipment reduce the setting out error from 15 mm to 10.3 mm. This reduces the barrier to using GNSS RTK equipment, minimizes human influence, enhances the work efficiency of setting out measurements, and ensures high efficiency and stability under complex conditions.

Comparison between aerial imagery and conventional cadastral mapping methods in Ekiti State Nigeria; towards a fit-for-purpose approach

Towards achieving Fit-for-Purpose (FFP) cadastral mapping, this study compares conventional cadastral mapping methods of theodolite traverse, total station and Real Time Kinematic Global Navigation Satellite System (RTK GNSS) with high-resolution aerial imagery in Ekiti State, Nigeria. Evaluating time, cost, accuracy, and coverage, it finds that high-resolution aerial imagery can achieve results comparable to conventional instruments with wider coverage, thereby expediting land registration and fostering sustainable development. However, challenges in obtaining high-resolution imagery necessitate regulatory reform for UAV use. The study recommends adoption of innovative solutions to improve the spatial, legal, and institutional frameworks in the state and enhance land governance.

Improving the fixed solution by processing the unmodeled errors in GNSS RTK long baseline positioning

Improving the fixed solution by processing the unmodeled errors in GNSS RTK long baseline positioning

Tightly coupled integration of vector HD map, LiDAR, GNSS, and INS for precise vehicle navigation in GNSS-challenging environment

ABSTRACT High-precision positioning and navigation are necessary for autonomous driving. GNSS RTK and INS integrated system is commonly used in vehicular navigation. But it suffers from severe signal reflections and blockages of GNSS signals and error accumulation of INS with MEMS-IMU in GNSS-challenging environment. In addition, high-definition (HD) maps in vector format and light detection and ranging (LiDAR) are two common options for intelligent vehicles. A tightly coupled localization method with vector HD map, LiDAR, GNSS RTK, and INS is proposed to take advantage of their complementary characteristics to accurately navigate a vehicle in a GNSS-challenging environment. The method is based on a particle filter (PF) framework. Lateral positions of particles are constrained by LiDAR measurements and lane information in the vector HD map. A constrained and damped LAMBDA searching method is proposed to update particle weights, aiming to find accurate longitudinal localization. Experimental results prove that our method can maintain sub-meter level horizontal positioning accuracy in GNSS-challenging environment, with improvements of (77%, 75%, 64% and 65%), regarding to three-dimensional position and yaw, compared to traditional GNSS-RTK/INS integration, while the improvement of the popular GNSS-RTK/INS/LiDAR integrated framework LIO-SAM is (16%, 53%, 48% and 51%).

Use of UAV imagery for land consolidation: analysis of the accuracy of the resulting orthophotomosaic in relation to the GNSS RTK measurement

Use of UAV imagery for land consolidation: analysis of the accuracy of the resulting orthophotomosaic in relation to the GNSS RTK measurement

Study on the positioning efficiency of GNSS RTK for road profile surveys - case study in Vietnam

Study on the positioning efficiency of GNSS RTK for road profile surveys - case study in Vietnam

Improving Urban Mapping Accuracy: Investigating the Role of Data Acquisition Methods and SfM Processing Modes in UAS-Based Survey Through Explainable AI Metrics

In this study, we investigated the accuracy of surface models and orthophoto mosaics generated from images acquired using different data acquisition methods at different processing levels in two urban study areas with different characteristics. Experimental investigations employed single- and double-grid flight directions with nadir and tilted (60°) camera angles, alongside the Perimeter 3D method. Three processing levels (low, medium, and high) were applied using SfM software, resulting in 42 models. Ground truth data from RTK GNSS points and aerial LiDAR surveys were used to assess horizontal and vertical accuracies. For the horizontal accuracy test, neither the oblique camera angle nor the double grid resulted in an improvement in accuracy. In contrast, when examining the vertical accuracy, it was concluded that for several processing levels, the tilted camera angle yielded better results, and in these cases, the double grid also improved accuracy. Feature importance analysis revealed that, among the four variables, the data acquisition method was the most important factor affecting accuracy in two out of three cases.

An Optimization-Based Indoor–Outdoor Seamless Positioning Method Integrating GNSS RTK, PS, and VIO

An Optimization-Based Indoor–Outdoor Seamless Positioning Method Integrating GNSS RTK, PS, and VIO

Beach surface model construction: A strategy approach with structure from motion - multi-view stereo

In contrast to traditional beach profiling methods like topographic surveys and GNSS, which pose significant challenges in terms of cost and time, this research underscores the efficiency, cost-effectiveness, and simplicity of terrestrial photogrammetry employing the Structure from Motion-Multi View Stereo (SfM-MVS) method. Notably, this approach enables the utilization of commonplace devices such as smartphones for data capture. The methodology integrates a 12-megapixel camera for image acquisition, processed through Agisoft Metashape Professional software, and validated for accuracy using ground control points (GCPs) and checkpoints (CKPs) calibrated via GNSS. Findings reveal substantial disparities in positional accuracy according to the Ground Control Points distribution. The study underscores the critical role of strategically distributing GCPs and CKPs in effectively mapping coastal areas, thus affirming the potential of SfM-MVS as a powerful and accessible tool for coastal monitoring initiatives. This research contributes significantly to advancing the efficiency and accessibility of beach profile monitoring, offering invaluable insights for researchers and practitioners in coastal management and environmental conservation efforts.•A simplified beach profile modeling methodology is proposed.•The method is faster and more cost-effective than traditional surveys (RTK GNSS, lidar, RPA).•The study highlights the importance of GCP and CKP distribution in enhancing SfM-MVS accuracy for coastal mapping.

GNSS ASSISTED PHOTOGRAMMETRIC RECONSTRUCTION FROM COMBINED 360° VIDEOS AND UAV IMAGES

Abstract. This paper introduces an integrated approach utilizing ground data consists of videos captured with a 360° (spherical) camera and aerial data acquired with a UAV equipped with a RTK GNSS module to reconstruct a portion of a small-town city center and/or a cultural heritage site. Previous research has demonstrated that image blocks oriented with RTK data on camera position can reach centimeter accuracies and can be efficiently used to reconstruct large areas and single monuments. However, some areas like porches, narrow passages and streets cannot be properly reconstructed from an aerial point of view. Conversely, ground-based 360° images offer detailed insights into the terrain and features that may be obscured from an aerial perspective. Integration of those two points of view can increase spatial resolution and coverage for 3D reconstruction. Indeed, the UAV captures large-scale features and topography, while ground-based 360° images focus on intricate details and ground-level characteristics. The possibility to exploit GNSS data acquired by UAV may also be used for GNSS-assisted image orientation with the aim of reducing or even avoiding, in specific situations, the need for GCPs. The paper explores practical applications of such data integration in the cultural heritage domain demonstrating the efficacy of the integrated approach in scenarios with complex architectures and inaccessible areas.

Research of measurement accuracy using GNSS RTK method for determining geodetic coordinates of vertical network points

Research of measurement accuracy using GNSS RTK method for determining geodetic coordinates of vertical network points

Quantifying the Reliability of Volumetric and Areal Calculation with UAV-Generated DEMs: A Comparative Study with Ground Truth Data

For performing an assessment of the volume estimation accuracy using Digital Elevation Models (DEMs) generated by Unmanned Aerial Vehicles (UAVs), an evaluation of suitability has been made. The study was operated at Tikrit University, on a man-made topographic depression in the form of fishponds. The generated DEM by using the images of the UAV followed by accuracy assessment using Ground Control Points (GCPs), the points distributed evenly throughout the pond. The results showed that the Root Mean Square Error (RMSE) calculated for the DEM at the optimum flight plane ranged between 0.14 to 0.45. Comparing the pond's predicted volume utilizing UAV DEMs to the ground truth volume obtained using GNSS RTK surveying, it was discovered that the UAV DEM calculation was 97% accurate. The study came to the conclusion that the UAV Structure from Motion (SFM) method and the generated DEMs are appropriate for precisely surveying the volumes utilizing the appropriate range of flying parameters based on prior knowledge.

Pilot study: Evaluating the feasibility of real‐time kinematic GNSS as a tool for tracking movable chairs in outdoor urban public spaces

AbstractAs urban public spaces evolve to accommodate human activities, there arises a pressing need for effective methodologies to understand public life within these environments. This pilot study assesses the accuracy of the Real‐Time Kinematic Global Navigation Satellite System (RTK GNSS) in the Toyohashi South Side Station Square, aiming to validate its utility as a privacy‐sensitive tool for studying public life, particularly in tracking movable chairs in urban settings. The findings indicate that RTK GNSS exhibits sufficient accuracy in recording the positions of movable chairs, thus facilitating public life studies. Given the variability of GNSS accuracy across environments, we propose the Silhouette Index as a metric for evaluating GNSS suitability across different scales. A Silhouette Index exceeding 0.9 signifies highly accurate data, suitable for comprehending the spatial arrangement and utilization of movable chairs in compact urban spaces. Conversely, an index below 0.8 indicates insufficient accuracy for this purpose. Nevertheless, RTK GNSS, akin to GPS, offers diverse applications in urban research. It can aid in analyzing pedestrian flows in city centers or expansive parks, as well as elucidating spatial behavioral patterns among distinct demographic groups in large‐scale urban public spaces.