Flat Terrain Research Articles

Unravelling spatiotemporal patterns of solar photovoltaic plants development in China in the 21st century

Solar energy, as an environmentally sustainable power source, is gaining increasing popularity worldwide, driving a surge in the number of solar photovoltaic (PV) plants. China, which has a prominent role in this domain, requires continuous updates to its PV plant data for spatiotemporal analyses. However, there remains an absence of a comprehensive and timely dataset of PV plants across China, leaving PV installation dates and other crucial attributes for comprehensive analyses underexplored. This study leverages Sentinel-2 data as a primary source to propose an optimized deep learning approach for PV plant extraction in China. Statistical analyses of PV plant attributes, including its installation date, size, site slope, and site land cover, were implemented from multiple data sources. Comprehensive analyses were conducted to unravel their spatiotemporal development patterns in the 21st century. The results indicate that as of 2023, China boasts 4347 PV plants, collectively spanning 4146 km2, which are predominantly concentrated in Northwest and North China. 2016 and 2017 marked substantial growth in China’s PV plants, while other years exhibited stability. These plants exhibit the distinct spatial characteristics of installing smaller PV plants on flat terrain covered by vegetation or barren land. Over time, a notable trend in the installation of China’s PV plants has been the increasing preference for establishing larger ones in smooth terrain, with a focus on preventing damage to natural resources. The results reveal China’s optimization of PV plant site selection and construction strategies, aligning with global environmental goals and sustainable energy practices.

Design of Wheelchair Drive Unit Capable of Driving on Roads and Obstacles with Shape Conversion

Wheelchairs are widely used globally and are essential for providing autonomy and mobility to elderly and disabled people who have movement restrictions. Manual wheelchairs require operation through turning the wheels or pushing the wheelchair directly, thus posing mobility limitations for the user and caregiver. In contrast, electric wheelchairs, when used by the user, allow for improved flexibility by operating the wheelchair through a single control mechanism. However, the use of electric wheelchairs poses challenges in accessing areas with stairs and curbs, limiting the range of activity and thereby diminishing the quality of life for users and those reliant on electric wheelchairs. The electric wheelchair developed in this research incorporates a single motor for lightweight design. It uses a wheel travel variation actuator, eliminating the need for synchronization and allowing for low-power operation. This design reduces power loss from the caterpillar’s idling during wheel movement and includes the implementation of a pulley system. The optimal pulley belt length was calculated, and a deceleration device was installed inside the caterpillar, enabling a design that is compact, lightweight, and capable of high deceleration. On paved roads and flat terrain, the electric wheelchair is designed for high-speed travel using two pairs of front omni wheels and drive wheels. For terrains with stairs, speed bumps, unpaved roads, and unavoidable obstacles, the wheelchair is powered by caterpillars. The electric wheelchair developed through the research presented in this paper has verified the reliability of its transmission system through gear stress and deformation analysis. Additionally, an electric wheelchair based on the proposed concept was constructed to validate the drivability, safety, operability, and convenience of its driving unit. Furthermore, a user rode the constructed electric wheelchair to confirm that there were no issues with its drivability.

Performance-Determining Variables of a Simulated Sprint Cross-Country Skiing Competition.

To investigate performance-determining variables of an on-snow sprint cross-country skiing competition and the evolvement in their relationship with performance as the competition progresses from the individual time trial (TT) to the final. Sixteen national-level male junior skiers (mean [SD] age, 18.6 [0.8]y; peak oxygen uptake [VO2peak], 67.6 [5.5]mL·min-1·kg-1) performed a simulated sprint competition (1.3km) in the skating style, comprising a TT followed by 3 finals (quarterfinals, semifinals, and final) completed by all skiers. In addition, submaximal and incremental roller-ski treadmill tests, on-snow maximal speed tests, and strength/power tests were performed. VO2peak and peak treadmill speed during incremental testing and relative heart rate, rating of perceived exertion, blood lactate concentrations, and gross efficiency during submaximal testing were all significantly correlated with performance in the TT and subsequent finals (mean [range] r values: .67 [.53-.86], all P < .05). Relative VO2peak and submaximal relative heart rate and blood lactate concentration were more strongly correlated with performance in the semifinals and final compared with the TT (r values: .74 [.60-.83] vs 0.55 [.51-.60], all P < .05). Maximal speed in uphill and flat terrain was significantly correlated with performance in the TT and subsequent finals (r values: .63 [.38-.70], all P < .05), while strength/power tests did not correlate significantly with sprint performance. VO2peak and high-speed abilities were the most important determinants of sprint cross-country skiing performance, with an increased importance of VO2peak as the competition format progressed toward the final.

The Relation between Geodiversity and Biodiversity of Al-Salman Depression, Al-Muthana Governorate, Southern Desert of Iraq

The study area is located in the southern desert of Iraq, near the Al-Salman Depression, about 130 km southwest of Al-Samawa City. The Collection of data of this study depends mainly upon field surveys, sample collection of rocks, soil, plants, and animals besides interviews with locals as well as photographing of interesting aspects. The geodiversity of the study area comprises geological features, geomorphological features, soil types, and water resources. The exposed rocks of study area are composed mainly of carbonate rocks, in addition to marl, sandstone, and claystone, which belong to the Middle member of the Dammam Formation (L. Eocene). The main landforms found near the Al-Salman area are flat terrain, depressions (faidhats), wadis, caves, and sinkholes. Three types of soils were recognized; silty clay, clayey silt, and sandy soils. The main water resources are the ephemeral streams (wadis), and water wells in sinkhole, besides the mechanical and hand-dug wells. Geodiversity features formed many habitats in the study area such as Wadi Al-Owja, depressions (faidhats), flat terrain, and sinkhole. The present study reveals that biodiversity includes a wide diversity of plants, invertebrates, and vertebrates. Some species were restricted to certain habitat types in the study area, while other species proved to be more generalist.

Landscape ecological risk assessment across different terrain gradients in the Yellow River Basin

The Yellow River Basin is an important ecological barrier zone in China, and the landscape pattern has changed greatly due to intense human activities. It is of great significance to explore the dynamic forecasting of ecological risk based on terrain gradient for the ecological security of the Yellow River Basin. In this study, the distribution characteristics of ecological risk from 2000 to 2040 are evaluated by CA-Markov and ERI models. We put forward a new method of landscape ecological risk assessment based on terrain gradient and further analyzed the relationship between ecological risk and terrain index. The results showed that the proportion of the cultivated land and the grassland in the Yellow River basin is more than 73%, with the largest dynamic change in 2020. The ecological risk in the study area showed a spatial pattern of “high in the northwest and southwest, low in the east and south-central.” During the study period, the overall ecological risk showed a decreasing trend, and the high risk was reduced by four times. The future ecological risk of all terrain gradient will show a decreasing trend, the high risks mainly occurred in areas with “flat terrain with low terrain gradient and low vegetation coverage.” This study will provide a new perspective for the dynamic forecasting of ecological risk and the analysis of the change of ecological risk through terrain gradients.

Modeling the Environmental Impact of Passenger Cars Driven on Hilly Roads in Austria: A More Accurate Valuation of Greenhouse Gas Emissions and Further Environmental Indicators for Integral Life Cycle Assessments of Road Infrastructures

Previous studies of road or railway infrastructures have shown that traffic emissions outweigh the environmental impacts of the product stage and construction stage over the entire life cycle. Traffic usage is therefore the main emitter over the life cycle (A1–C4). Due to the small number of sustainability assessment systems, the question of how to consider traffic emissions in detail in an integral life cycle assessment has arisen. This study examines Austrian car traffic and investigates environmental impacts beyond the scope of carbon dioxide and particulate matter. The results were determined for a selection of common impact indicators. In addition to driving in flat terrain, an approach is presented that enables the evaluation of emissions due uphill and downhill driving. Thus, route options and route closures/detours due to maintenance work can be evaluated in a simple way. During the analyses, a traffic calculator was developed, which can currently assess different cars depending on the route specifics (flat/hill). The tool can be expanded to include other road vehicles (buses, trucks, motorcycles) and trains as well. This will simplify evaluations and decision-making processes and provide optimal support for a future-proof sustainable built environment.

Breakdown of the velocity and turbulence in the wake of a wind turbine – Part 1: Large-eddy-simulation study

Abstract. A new theoretical framework, based on an analysis in the moving and fixed frames of reference (MFOR and FFOR), is proposed to break down the velocity and turbulence fields in the wake of a wind turbine. This approach adds theoretical support to models based on the dynamic wake meandering (DWM) and opens the way for a fully analytical and physically based model of the wake that takes meandering and atmospheric stability into account, which is developed in the companion paper. The mean velocity and turbulence in the FFOR are broken down into different terms, which are functions of the velocity and turbulence in the MFOR. These terms can be regrouped as pure terms and cross terms. In the DWM, the former group is modelled, and the latter is implicitly neglected. The shape and relative importance of the different terms are estimated with the large-eddy-simulation solver Meso-NH coupled with an actuator line method. A single wind turbine wake is simulated on flat terrain, under three cases of stability: neutral, unstable and stable. In the velocity breakdown, the cross term is found to be relatively low. It is not the case for the turbulence breakdown equation where even though the cross terms are overall of lesser magnitude than the pure terms, they redistribute the turbulence and induce a non-negligible asymmetry. These findings underline the limitations of models that assume a steady velocity in the MFOR, such as the DWM or the model developed in the companion paper. It is also found that as atmospheric stability increases, the pure turbulence contribution becomes relatively larger and pure meandering relatively smaller.

Virtual Shake Robot: Simulating Dynamics of Precariously Balanced Rocks for Overturning and Large-displacement Processes

Understanding the dynamics of precariously balanced rocks (PBRs) is important for seismic hazard analysis and rockfall prediction. Utilizing a physics engine and robotic tools, we develop a virtual shake robot (VSR) to simulate the dynamics of PBRs during overturning and large-displacement processes. We present the background of physics engines and technical details of the VSR, including software architecture, mechanical structure, control system, and implementation procedures. Validation experiments show the median fragility contour from VSR simulation is within the 95% prediction intervals from previous physical experiments, when PGV/PGA is greater than 0.08 s. Using a physical mini shake robot, we validate the qualitative consistency of fragility anisotropy between the VSR and physical experiments. By overturning cuboids on flat terrain, the VSR reveals the relationship between fragility and geometric dimensions (e.g., aspect and scaling ratios). The ground motion orientation and lateral pedestal support affect PBR fragility. Large-displacement experiments estimate rock trajectories for different ground motions, which is useful for understanding the fate of toppled PBRs. Ground motions positively correlate with large displacement statistics such as mean trajectory length, mean largest velocity, and mean terminal distance. The overturning and large displacement processes of PBRs provide complementary methods of ground motion estimation.

Extreme Value Analysis for Peak Heliostat Wind Load Predictions

This study investigated high-frequency load fluctuations on a rectangular heliostat model in a boundary layer wind tunnel experiment. Statistical methods for peak wind load predictions were compared with load distributions through load cell and surface pressure measurements on the heliostat model placed in two simulated atmospheric boundary layers (ABLs) representing a flat desert terrain and open country terrain. It was found that statistical peak predictions based on horizontal wind gust velocity amplitude underestimates the load coefficients in stow and at oblique azimuth angles for maximum azimuth moments. In addition, it was shown that the distributions of the centre of pressure position and the hinge moment in stow position are non-Gaussian. It is therefore recommended that the frequency and amplitude of the vertical wind velocity component must be considered for peak load predictions of hinge moments and azimuth moments.

Pedestrian dynamics on slopes: Empirical analysis of level, uphill, and downhill walking

Pedestrian safety on inclined walking facilities merits greater attention than that on level surfaces. Crowd accidents and domino effects are more likely to occur on slope walkways, especially at high crowd densities, as in the tragic case of the 2022 Itaewon Halloween crowd crush in South Korea. However, experimental investigations of the pedestrian dynamics on slopes with varying inclinations are scarce. In this study, a controlled experiment involving 48 participants was conducted to investigate the differences in pedestrian movement characteristics during level, uphill, and downhill slope walking. A wide range of slope inclinations was considered, namely 0°, 3°, 7°, 12°, 17°, and 22°. The results demonstrated that walking speeds uphill are lower than those on flat terrains, and uphill speeds decrease with increasing inclination. In contrast, increased slope inclinations do not always correspond to reduced downhill speeds. Notably, at inclinations of 3° and 7°, the downhill speed exceeds that of level walking, suggesting that a mild downhill slope can facilitate faster movement. Compared with downhill walking, pedestrians exhibit more lateral motion and significantly lower speeds (p < 0.01) when walking uphill at the same inclination. However, the average flow rate during downhill walking is lower than those observed on flat ground and uphill terrain. This difference may be attributable to the lower pedestrian density during downhill walking to reduce the likelihood of falling. These findings can enhance the understanding of pedestrian dynamics on ramps and have significant implications for the design of safer inclined walking facilities and prevention of potential disasters on such walkways.

Characterization of sewage quality and its spatiotemporal variations in a small town in Eastern Guangdong, China

The domestic sewage in rural areas of South China is characterized by a relatively low concentration of organic pollutants; however, the factors causing this have not been carefully examined. This study conducted a comprehensive survey on two sewer networks in a small town of Eastern Guangdong, China, via grab water sampling at a frequency of once every 2 weeks lasting for 1 year. The sewage quality showed significant variations across the systems, while a gradual decrease in the concentrations of chemical oxygen demand (COD), total nitrogen (TN) and phosphorus (TP) from the upper to lower reaches of sewers could be observed. Storm events could have a flushing effect on TP in the upper reach of sewers, but a dilution effect on COD and TN in flat terrains. The diurnal pattern of sewage was largely impacted by the position of the manholes and water consumption difference between holidays and normal days. Both COD/TN and TN/TP ratios of the sewage showed a lognormal distribution dominating in the range of 2.0–3.0 and ~10.0, respectively. The low ratio of COD/TN in the morning discharge peak could be attributed to the wide use of septic tanks in the area, while groundwater infiltration played more important roles in the basal flow conditions. This study could serve as a basic reference for designing and managing sewage infrastructure in rural areas of South China and highlights that prevention of groundwater infiltration is crucial to improve the efficiency of sewage infrastructure in high water table areas.

Numerical modeling and simulation of cable barriers under vehicular impacts on a sloped median

Cable barriers are flexible barrier systems that are commonly used as median barriers in the United States for their general effectiveness and low installation and maintenance costs. The current cable median barrier (CMB) adopted by the North Carolina Department of Transportation was previously evaluated on flat terrain and found to satisfy the requirements of the National Cooperative Highway Research Program Report 350. Under in-service conditions (i.e., on a sloped median), the current CMB failed to stop small passenger cars in many incidents. The new roadside safety standard, Manual for Assessing Safety Hardware (MASH), recommends that CMBs be tested and/or evaluated on sloped medians. However, conducting full-scale crash tests on sloped median is extremely difficult and few experimental studies exist. In this study, finite element simulations were used to evaluate the performance of the current CMB design on a 6H:1V sloped median under MASH Test Level 3 conditions. To address the issue of vehicle underriding on the current CMB, two retrofit designs were developed and also evaluated on the sloped median. Two MASH compliant vehicles, a 1996 Dodge Neon and a 2006 Ford F250, were used to evaluate all three CMBs from both frontside and backside and with two initial impact points. The MASH exit-box criterion, MASH Evaluation criteria A, D, and F, vehicular responses, exit angles, and residual velocities were used to evaluate the CMB performance for structural adequacy, occupant risk, and post-impact trajectories. The simulation results showed that one of the retrofit designs could improve the CMB performance on a sloped median at MASH Test Level 3 conditions.

Terra-22: an aerial soil sampling in densely compacted agricultural fields

Soil sampling is used in agriculture to monitor fields and plan fertilizer application. This task is typically performed manually, but ground robots have recently been introduced. However, ground robots are often slow and heavy, which contributes to soil compaction. Fast-flying drones could provide an interesting alternative to ground robots. However, drones are severely limited in their payload and in the forces that they can apply to the soil. This paper presents the Terra-22, the first airborne system capable of sampling densely compacted agricultural soils. To do so, many challenges were addressed, including the development of (i) a high-power density drilling system that outperforms typical brushed DC gear motor by 39%, (ii) a drill design that is 48% lighter than traditional steel auger drills and that keeps cross-contamination under 4%, and (iii) a drill penetration rate controller that reduces the torque requirement by 33% and the axial force requirement by eight folds when compared to a constant penetration speed controller. Outdoor soil sampling tests in a corn field (sandy loam soil, compaction between 0.8 and 2 MPa) demonstrated a 94% success rate on flat terrain and a sampling duration under one minute.

Hydrogeological Implications of Slope and Land Use/Land Cover Distribution in Part of Southern, Nigeria

The study focuses on the hydrogeological implications of slope and Land Use/Land Cover (LULC) distributions in the Aniocha and Oshimili regions of Nigeria. Understanding the spatial variations in these parameters is critical for effective groundwater management and sustainable land use planning in these areas. The aim is to assess the spatial distribution of slopes and LULC types and their impact on groundwater recharge and surface runoff in the study area. The study employs spatial analysis techniques to categorize slope data into five classes and LULC data into seven types for the years 2017 and 2023. The analysis covers Aniocha North, Aniocha South, Ika North, Ika South, Oshimili North, and Oshimili South. The slope analysis reveals that the largest area (1022.73 km²) falls within the 0-1.52° slope category, indicating predominantly flat terrain with high infiltration potential. The LULC analysis shows that in 2017, trees covered the most extensive area (2143.21 km²), which decreased to 1573.76 km² by 2023, indicating significant deforestation. Built areas expanded from 281.76 km² to 391.99 km², reflecting increased urbanization. Flat terrains (0-3.51°) are conducive to groundwater recharge due to their high infiltration rates, whereas steeper slopes (3.51-26.00°) exhibit higher runoff potential, impacting groundwater recharge negatively. The reduction in tree cover and expansion of built areas have significant hydrogeological implications. Deforestation reduces groundwater recharge potential, while urbanization increases surface runoff, potentially leading to flooding and reduced groundwater levels. The study highlights the need for integrated land and water management strategies to balance development with environmental sustainability. Protecting and managing flat areas for groundwater recharge, implementing soil conservation in steeper regions, and promoting sustainable agricultural practices are essential. Urban planning should incorporate green infrastructure to mitigate the impacts of increased impervious surfaces. This study provides a comprehensive analysis of slope and LULC changes over time and their hydrogeological implications, offering valuable insights for sustainable land and water resource management in the Aniocha and Oshimili regions.

Finite-frequency modeling of regional tropospheric infrasound using realistic atmospheres and terrain.

Infrasonic waves have been observed to propagate to regional (greater than 15 km) distances through the troposphere. Infrasound propagation in the geometric acoustics approximation has shown that realistic terrain can scatter acoustic energy from tropospheric ducts; however, ray methods cannot intrinsically capture finite-frequency behavior such as diffraction. A two-dimensional finite-difference time-domain (FDTD) method has been developed to solve linearized equations for infrasound propagation with realistic terrain. Acoustic wave propagation over 100 km with both flat terrain and a Gaussian hill was first simulated in order to compare finite-frequency propagation with ray predictions. The effects of realistic terrain and atmospheres on infrasound signals from a 2012 surface explosion at the Utah Testing and Training Range are then investigated. Propagation through the troposphere is suggested by array processing results, but eigenrays are not predicted due to weak to nonexistent ducting conditions. FDTD modeling suggests that the inclusion of terrain and finite frequency effects helps explain much of the observed signal in a realistic scenario. These results suggest that geometric acoustics may underestimate propagation through the troposphere, and that recorded waveforms at regional distances may be noticeably affected by terrain.

Geology and Landslide Susceptibility Using GIS at Kampung Belahat, Jeli, Kelantan

The geological study of Kampung Belahat in Jeli, Kelantan, Malaysia, which is located close to the Thai border in northeastern Peninsular Malaysia, is the main subject of this research. The Jeli district, which spans an area of roughly 2,552 square kilometers, has three different geomorphological types: low, hills, and mountainous. Kampung Belahat is surrounded by a mix of flat, hilly, and mountainous terrain due to the area’s height range of 80m to 900m. The goal of the study is to update Kampung Belahat’s geological map, with a particular emphasis on geomorphology, lithology, and structural geology and to determine the landslide susceptibility of study area. Comprehensive geological data was gathered by laboratory work, sampling, and traversing during the geological mapping process. The area’s lithology consists of high-grade metamorphic rock types and intrusive igneous rock, with granite and gneiss being the main rock types. The granite rock shows signs of metamorphic processes, including 33% biotite, 46% quartz, 11% alkali feldspar, and 10% plagioclase. Gneiss rock, on the other hand, has flattened minerals as a result of metamorphism; it contains 13% alkali feldspar, 35% quartz, and 52% biotite. Granite was the primary geological structure observed, combined with visible quartz veins and joint and fault structures. The study took into account five factors: aspect, drainage density, lithology, slope, and land use. The Weightage Overlay Method (WOM) was used to process the data. The study area is categorized into three risk levels on the resulting landslide susceptibility map: low (5%), moderate (30%), and high (65%). This knowledge is essential for putting safety precautions in place, reducing potential harm during future development in the area, and reducing the likelihood of landslides.

Modeling the Topographic Effect on Directional Anisotropies of Land Surface Temperature from Thermal Remote Sensing

In mountainous surfaces, land surface temperature (LST) plays a vital role in surface energy budget and vegetation–soil ecosystems. Despite advancements in retrieving LST from thermal infrared measurements at various spatial and temporal scales, accurately estimating LST for complex terrain remains challenging. This challenge arises from the conflict between the topographic effect and the assumption of flatten surface in many existing studies. In the absence of a simple and practical model for the topographic effect on the directional anisotropies of LST (LSTDA) over mountainous areas, the equivalent slope method is introduced to bridge the gap between studies conducted on flat surfaces and complex terrain. The proposed thermal equivalent slope kernel-driven (TESKD) model is validated using measurements and simulations from an unmanned aerial vehicle (UAV) system and a 3-dimensional raytracing model, respectively. Results indicate the following: (a) Under varying topographic conditions, vegetation cover, and solar zenith angles, there is a significant impact of topography on LSTDA. The average effect is greater than 0.5 K and can reach up to 1.5 K at the higher solar zenith angle (50°). (b) Based on UAV data, TESKD provides a better explanation and fitting effect for LSTDA in 3 typical mountainous surfaces including valley, peak, and solo-slope, with an average root mean square error (RMSE) of 0.27 K and an average coefficient of determinations of 0.628 of the 3 conditions, compared to a flat model (0.35 K and 0.335). (c) Based on simulations, TESKD exhibits more than a 30% improvement in accuracy, and for sparsely vegetated surfaces, the difference in RMSE can be up to 0.8 K when considering the topographic effect compared to not considering it. The new model can help to understand the radiative transfer process in heterogeneous mountainous surfaces and serves as a valuable tool for studies associated with water and carbon cycles.

Short-Term Prediction of Vertical Deformation in Tidal Flat Terrains Based on PSO-VMD-LSTM

Short-Term Prediction of Vertical Deformation in Tidal Flat Terrains Based on PSO-VMD-LSTM

The effect of surface topography on the ball-rolling ability of Kheper lamarcki (Scarabaeidae).

The most effective way to avoid intense inter- and intra-specific competition at the dung source, and to increase the distance to the other competitors, is to follow a single straight bearing. While ball-rolling dung beetles manage to roll their dung balls along nearly perfect straight paths when traversing flat terrain, the paths that they take when traversing more complex (natural) terrain are not well understood. In this study, we investigate the effect of complex surface topographies on the ball-rolling ability of Kheper lamarcki. Our results reveal that ball-rolling trajectories are strongly influenced by the characteristic scale of the surface structure. Surfaces with an increasing similarity between the average distance of elevations and the ball radius cause progressively more difficulties during ball transportation. The most important factor causing difficulties in ball transportation appears to be the slope of the substrate. Our results show that, on surfaces with a slope of 7.5deg, more than 60% of the dung beetles lose control of their ball. Although dung beetles still successfully roll their dung ball against the slope on such inclinations, their ability to roll the dung ball sideways diminishes. However, dung beetles do not seem to adapt their path on inclines such that they roll their ball in the direction against the slope. We conclude that dung beetles strive for a straight trajectory away from the dung pile, and that their actual path is the result of adaptations to particular surface topographies.

A robust particle filter for ambiguous updates of underwater terrain-aided navigation

This paper proposes a novel method to improve the robustness of particle filtering (PF) in relatively flat terrain that lack sufficient features for accurate positioning. In terrain -aided navigation (TAN), similar terrain profiles lead to multimodality in the posterior distribution. It not only reduces the accuracy of current position estimation, but also affects the subsequent estimation of PF, and even causes filter divergence. When no additional information is available, the historical estimation is employed to correct ambiguous updates caused by multimodal posteriors. First, a strategy for identifying ambiguous updates is proposed by analyzing the particle set distribution using the clustering method and covariance. Inspired by out-of-sequence measurement (OOSM), once the ambiguous updates are detected, the ambiguous estimates are corrected by introducing high-quality previous information. Moreover, an efficient solution is provided for the storage and computation requirements of OOSM within the PF framework. To verify the effectiveness of the proposed algorithm, simulation and experimental validation are designed. By comparing with PF, mixture particle filtering (MPF), and OOSMPF algorithms, the proposed algorithm demonstrates better estimation accuracy and robustness in terrain flat areas.