Differential GPS Research Articles

Higher than present global mean sea level recorded by an Early Pliocene intertidal unit in Patagonia (Argentina)

Reconstructions of global mean sea level from earlier warm periods in Earth’s history can help constrain future projections of sea level rise. Here we report on the sedimentology and age of a geological unit in central Patagonia, Argentina, that we dated to the Early Pliocene (4.69–5.23 Ma, 2σ) with strontium isotope stratigraphy. The unit was interpreted as representative of an intertidal environment, and its elevation was measured with differential GPS at ca. 36 m above present-day sea level. Considering modern tidal ranges, it was possible to constrain paleo relative sea level within ±2.7 m (1σ). We use glacial isostatic adjustment models and estimates of vertical land movement to calculate that, when the Camarones intertidal sequence was deposited, global mean sea level was 28.4 ± 11.7 m (1σ) above present. This estimate matches those derived from analogous Early Pliocene sea level proxies in the Mediterranean Sea and South Africa. Evidence from these three locations indicates that Early Pliocene sea level may have exceeded 20m above its present level. Such high global mean sea level values imply an ice-free Greenland, a significant melting of West Antarctica, and a contribution of marine-based sectors of East Antarctica to global mean sea level.

Kinematic State Estimation Using Multiple DGPS/MEMS-IMU Sensors

Inertial measurement unit based motion capture (MOCAP) technology has put an end to subjective gait analysis and has allowed researchers to obtain quantitative measurements of the kinematic and kinetic variables associated with gait. However, these systems are prone to drift in the inertial frame, especially under conditions of high acceleration, which naturally occur during rapid maneuveres. In an effort to circumvent this, we explore the possibility of integrating differential global positioning systems (DGPSs) on each limb of interest. This novel configuration is compared to a traditional inertial based system as well as a popular method of differential global positioning systems (DGPS) processing (RTKLIB) by means of an extended Kalman smoother. The configurations are experimentally validated on a mechanical test rig with the effect of nonline of sight of the global navigation satellite systems antennae explored. The results demonstrate that the combination of multiple DGPS receivers facilitate improved accuracy of the multibody system during rapid acceleration movements and can improve the accuracy of future Motion capture (MOCAP) systems.

Study The Effect of High Voltage Power Lines on The Results of Differential Static - GPS Applications (Dept.c)

Some surveyors claimed that problems were experienced when one collects GPS observations beneath high voltage power lines. They had reported quite large anomalies. Still others had reported no problems beneath high voltage power lines. The current papers study the effect of High Voltage Power Lines HVPL on Differential Static GPS observations and results. The research introduces the comparative study for the results of a GPS network. The cases of study are chosen to illustrate the effect of different types and location of high voltage tower lines. Although the results of GPS network analysis have shown a very high accuracy away from tower lines, the worst case discrepancies in elevation ranged between 4 cm to 18 cm under or dear tower lines, and small values discrepancies in east and north (2-8) mm in position of points. Finally, available conclusions andrecommendations are obtained.

Ecological factors affecting the fitness of the threatened orchid Anacamptis robusta (Orchidaceae): Habitat disturbance, interactions with a co-flowering rewarding orchid and hybridization events.

The food-deceptive species Anacamptis robusta is threatened in the Balearic Islands, and its habitat has recently been transformed through human disturbance. This study investigated how human disturbance affects the reproductive output of A. robusta and how its fitness is affected by competition with rewarding relatives, fungal infections and hybridization processes. To evaluate the impact of habitat loss on plant fitness, data on reproductive measures were obtained in two well-conserved subpopulations and the unique disturbed subpopulation. Photo-trapping cameras were installed to determine the floral visitation rate. All flowering individuals in 2019 were georeferenced using differential GPS to examine the influence of geospatial patterns on the reproductive success of A. robusta. In addition, hand-pollination treatments were performed to evaluate the hybridization between A. coriophora and A. robusta and the origin of A.×albuferensis. The human-disturbed subpopulation of A. robusta had a lower fruit set success than the subpopulations in well-conserved areas. The presence of A. coriophora is negatively affecting the reproductive output of A. robusta. Moreover, A. robusta can only act as the pollen donor during hybridization. The complexity of the ecological system, which is enhanced by the strong pollinator dependence of the threatened species, must be considered when making conservation decisions. Although human disturbance directly affects plant population stability, other ecological issues must be considered, such as pollinator interaction, interspecific competition for pollinators, fungal infection and hybridization events.

Slip rates and paleoearthquakes along the east segment of the Guanggaishan–Dieshan fault zone, West Qinling Range, NW China

The WNW-trending Guanggaishan–Dieshan fault (GDF) is located in the West Qinling Range at a site of tectonic junction between the Tibetan plateau, the Sichuan basin and the Ordos block. Tectonically, this region is bounded by the East Kunlun fault to the southwest, the West Qinling fault to the north, and the Longmenshan fault to the southeast. The activity of the GDF is essentially related with the northeastward expansion of the Tibetan Plateau and associated strain partition between the East Kunlun fault and the West Qinling fault. This study reported the sense of fault movement, rate of fault slip, and the timing of three paleoseismic events on the east segment of the Guanggaishan–Dieshan fault (EGDF) with which no historical earthquake has been documented before. We focused our investigation on three branch faults in the central part of the EGDF using a range of study methods, e.g. structural mapping, paleoseismological trenching, unmanned aircraft vehicle photogrammetry, differential GPS survey, as well as radiocarbon and optically stimulated luminescence dating. Our new results highlighted: (1) the EGDF is dominated by the left-lateral sense of movement with a minor component of dip slip, (2) the range-bounding branch is characterized by a maximum left-lateral slip rate of 0.72 ± 0.34 mm/year and a maximum vertical-slip rate of 0.13 ± 0.03 mm/year, respectively. Kinematics of the EGDF is similar to many other active faults in the West Qinling Range, together they play a joint role in accommodating and transferring the residual left-lateral slip of the East Kunlun Fault. Three paleoseismic events were identified on the range-bounding fault based on two types of event markers: cut-cover relation and colluvial deposition. The ages of the most recent two events are estimated to be 2765–3320 cal. year BP and 12,775–13,005 cal. year BP and the age of the oldest event is as early as 18,495–32,950 cal. year BP. In contrast, there is no compelling evidence to show paleoseismic event along the rest two branches, and further work is needed to demonstrate this.

Correction of water column height variation on 2D grid high-resolution seismic data using dGPS based methodology

Variations in the physical properties of water column usually impede exact water column height correction on high-resolution seismic data, especially when the data are collected in shallow marine environments. Changes in water column properties can be attributed to variation in tides and currents, wind-generated swells, long and short amplitude wave-fronts, or variation in salinity and water temperature. Likewise, the proper motion of the vessel complicates the determinability of the water column height. This study provides a less time-consuming and precise differential Global Positioning System based methodology that can be applied to most types of high-resolution seismic data in order to significantly improve the tracking and quality of deduced geological interpretations on smaller depth scales. The methodology was tested on geophysical profiles obtained from the German sector of the North Sea. The focus here was to identify, distinguish and classify various sub-surface sedimentary structures in a stratigraphically highly complex shallow marine environment on decimeter small-scale. After applying the correction to the profiles, the sea floor, in general, occurs 1.1 to 3.4 m (mean of 2.2 m) deeper than the uncorrected profiles and is consistent with the sea floor from published tide corrected bathymetry data. The corrected seismic profiles were used in plotting the depth of the base of Holocene channel structures and to define their gradients. The applied correction methodology was also crucial in glacial and post-glacial valley features distinction, across profile correlation and establishing structural and stratigraphic framework of the study area.

A marker-free method for structural dynamic displacement measurement based on optical flow

Information on dynamic displacement is an effective indicator for structures condition evaluation and provides a quantised insight into the structural analysis. This paper proposes a low-cost system based on computer vision using a smartphone to measure dynamic displacement, and then identify the dynamic properties of structures. Conventional sensors like linear variable differential transformers (LVDT), GPS, and accelerometer in monitoring systems have limitations of high price, inaccessibility, and accuracy. However, some new technologies eliminate these disadvantages. For example, a smartphone with a high-resolution camera becomes more affordable, which is regarded as appropriate equipment for structural health monitoring (SHM). Based on the optical flow, this method allows users to track points with a specific interval in the chosen region and reduces the displacement drift induced by the Kanade–Lucas–Tomasi (KLT) method. With the method applied, the region of interest is relocated according to pixel motion, and feature points are reselected. The accuracy of the system is verified on a laboratory suspension bridge model, and the results of modal frequency are confirmed with an accelerometer and FEM simulations.

Small-UAV Radar Imaging System Performance with GPS and CDGPS Based Motion Compensation

The present manuscript faces the problem of performing high-resolution Unmanned Aerial Vehicle (UAV) radar imaging in sounder modality, i.e., into the vertical plane defined by the along-tack and the nadir directions. Data are collected by means of a light and compact UAV radar prototype; flight trajectory information is provided by two positioning estimation techniques: standalone Global Positioning System (GPS) and Carrier based Differential Global Positioning System (CDGPS). The radar imaging is formulated as a linear inverse scattering problem and a motion compensation (MoCo) procedure, accounting for GPS or CDGPS positioning, is adopted. The implementation of the imaging scheme, which is based on the Truncated Singular Value Decomposition, is made efficient by the Shift and Zoom approach. Two independent flight tests involving different kind of targets are considered to test the imaging strategy. The results show that the CDGPS supports suitable imaging performance in all the considered test cases. On the other hand, satisfactory performance is also possible by using standalone GPS when the meter-level positioning error exhibits small variations during the radar integration time.

Coastal Boulders on the SE Coasts of Cyprus as Evidence of Palaeo-Tsunami Events

Cyprus has a long history of tsunami events, as noted by archaeological and geological records. At Cape Greco (southeastern Cyprus) large boulders have been noted, however, no detailed geomorphological research has taken place so far and the related high energy event was undated until now. Our research aims to record in detail and interpret these large boulders deposits. The boulders, located between ≈3 and 4.5 m a.m.s.l., are fragments of an upper Pleistocene aeolianite, which is overlaying unconformly a lower Pleistocene calcarenite. Dimensions and spatial distribution of 272 small, medium, and large boulders were documented, while their precise distance from the coastline was recorded by field mapping and remote sensing, using Differential GPS (DGPS), drone, and Geographic Information Systems (GIS) technics. Field data were subsequently combined with hydrodynamic equations, in order to determine the extreme event(s) that caused their transport inland, and radiocarbon dating was accomplished on three samples of Vermetus sp. to determine the chronological context. Our findings appear to broadly correlate with the 1303 AD tsunami, which has displaced at least part of the studied boulders, and one other undocumented event at AD 1512-1824. The large number of boulders and sizes in our study area further indicate that their dislocation is most likely owed to multiple events from various sources.

Application of UAV Remote Sensing Technology for Sand Quarry Volumetric Audit and Environmental Impact Assessment: A Case Study Done in Neyvasal Sand Quarry, Cuddalore District, Tamil Nadu—India

Illicit sand quarry in riverbeds will become a menace to the worldwide environment and will lead to changes in the river morphology, physical habitation and ecosystem. The excavation of sand in the riverbed is essential because it helps to maintain the river path and avoid flood inundation during the rainy season. But the excess sand removal only creates a negative impact to the surrounding environment. Hence, effective monitoring and scientific audit method are required to identify the illicit sand quarry. The assessment of excess sand excavated area and volume is a major task for the Economic and Revenue Sector Audit (E&RSA) officials. Also, the volume calculation of sand quarry is a tedious and time-consuming process when using a traditional survey instrument like total station. Integration of unmanned aerial vehicle (UAV) remote sensing (R/S) technology with modern survey instrument like differential global positioning system (DGPS) will reduce the survey time, cost and manpower. In this study, the UAV-based aerial survey and DGPS observation were done in Economic and Revenue Sector Audit (E&RSA), a specified sand quarry site. The acquired UAV aerial images and DGPS points were subsequently used to generate orthomosaic map, digital terrain model (DTM), digital surface model (DSM) and 3D mesh. The UAV-derived outputs have been compared with lease map and revenue records. All the findings related to violations in approved lease boundary, volume and depth were reported to E&RSA to estimate the revenue loss to the government.

Comparison of different digital elevation models for drainage morphometric parameters: a case study from South India

With a plethora of digital elevation models (DEM) available for elevation extraction and catchment morphometric analysis, it is essential to compare and investigate their accuracy and parameter uncertainty derived from them. To serve that purpose, in this study, we have compared the DEMs of different resolution obtained from Shuttle Radar Topography Mission (SRTM), CARTOSAT, and topographic maps (1:25000) in terms of vertical accuracy and morphometric parameters. The investigation was performed on a sub-basin of Champavathi River which is located in Andhra Pradesh, the southern part of India. The vertical accuracy of the DEMs was estimated using elevation from about 1180 points obtained from the Differential Global Positioning System (DGPS) survey. The morphometric analysis showed that the basin is elongated with low relief ratio, mild/rolling slopes, and medium drainage density, and the results were comparable from different DEM sources indicating that most of the morphometric parameters were not significantly dependent on the scale and source of the DEM. Further, vertical accuracy estimation showed that the CARTOSAT DEMs (10 m and 30 m) have a lower root mean square error (4.53 m and 5.89 m) when compared with the SRTM DEMs (6.11 m and 7.19 m).

Late Quaternary Tectonic Activity and Slip Rates of Active Faults in the Western Hexi Corridor, NW China

The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward extension of the Altyn Tagh fault. Based on geological and geomorphologic field survey, trench excavation, optically stimulated luminescence dating, we define the fault geometry and kinematic properties of the two faults. Based on fault scarps measurement using differential GPS and 10Be surface exposure dating, we determined vertical slip rate of 0.09±0.01 mm/yr for the Yinwashan fault and 0.1±0.02 mm/yr for the Xinminpu fault. Using the dips observed in trenches and natural sections, we estimated horizontal shortening rates of 0.05±0.03 and 0.23±0.06 mm/yr, respectively. No significant strike slip motion is observed on these two faults, and we infer that this region was dominated by horizontal shortening in the Late Quaternary. Although the shortening rate is quite low on each individual fault, together with other faults in this area, these two faults have an essential role in transferring slip from the eastern end of the Altyn Tagh fault and in accommodating the northeastward growth of Tibetan Plateau.

Measuring the Electron Density Roughness of the D‐Region Ionosphere

AbstractWe present a method of characterizing the horizontal and vertical electron density roughness of the D‐region ionosphere using Nationwide Differential Global Position System (NDGPS) transmitters as low‐frequency (LF; 30–300 kHz) and medium‐frequency (MF; 300–3,000 kHz) signals of opportunity. The horizontal roughness is characterized using an amplitude cross‐correlation method, which yields the correlation length scale metric. The vertical roughness is characterized using a differential phase height, which is needed to mitigate the effects of transmitter phase instability. The ranges and typical values of roughness metrics are investigated using data from several field campaign measurements. Finally, the roughness metrics for an NDGPS transmitter and very low frequency (VLF) transmitter are compared. It is found that the roughness detected by the VLF transmitter is significantly smoother and demonstrates the utility of this method to complement traditional VLF measurements.

Spatial Heterogeneity of Surface Topography in Peatlands: Assessing Overwintering Habitat Availability for the Eastern Massasauga Rattlesnake

The eastern massasauga rattlesnake (Sistrurus catenatus) relies on small-scale differences in peatland surface elevation to survive harsh overwintering conditions at the northern limit of its range. We characterized the spatial heterogeneity of surface topography in peatlands within the eastern Georgian Bay rock barrens landscape of Ontario, Canada, to assess available snake overwintering habitat. At six peatlands, we used a differential global positioning system to collect surface-elevation data. We created spatially-explicit surface models to map peatland surface topography, quantify habitat that was likely to remain unflooded during the overwintering period, and identify key characteristics associated with greater habitat availability. While surface elevations were spatially heterogeneous within and among sites, larger peatlands were associated with greater surface spatial variability relative to the lowest elevation measured within each site. However, even peatlands with very little spatial heterogeneity (average of 0.24 m above lowest elevation), provided unflooded overwintering habitat. Inter-annual weather conditions and peatland and watershed characteristics likely control the availability and distribution of unflooded overwintering habitat. We found that trees, specifically white pine (Pinus strobus) and maple (Acer spp.), were spatially associated with higher surface elevations and could be used to identify areas of unflooded winter habitat. Our findings are useful for landscape-scale assessments of available overwintering habitat to prioritize conservation and management efforts.

A Study on the Evaluation Method of Highway Driving Assist System Using Monocular Camera

In this paper, we propose a method to evaluate Highway Driving Assist (HDA) systems, a type of Advanced Driver Assistance System (ADAS), using a monocular camera, which eliminates the need of experts or expensive equipment and reduces the time, effort, and cost required in such tests. We use the information from the images captured by the monocular camera, such as the lane and rear tires of the lead vehicle, and from the geometrical composition, including the heading angle and the distance of the camera from the front bumper of the test vehicle. To verify the evaluation method, we used the image and geometric information to calculate the distances of the lead vehicle and the lane center from the test vehicle. We compared and analyzed the method using DGPS (Differential Global Positioning System), Data Acquisition(DAQ) and the method using monocular camera. Therefore, it was determined that the proposed method of evaluating HDA systems using a monocular camera is reliable because of the small margin of error between the theoretical with monocular camera and real vehicle test with DAQ and DGPS.

Aircraft positioning using DGNSS technique for GPS and GLONASS data

Purpose The purpose of this paper is to present the problem of implementation of the differential global navigation satellite system (DGNSS) differential technique for aircraft accuracy positioning. The paper particularly focuses on identification and an analysis of the accuracy of aircraft positioning for the DGNSS measuring technique. Design/methodology/approach The investigation uses the DGNSS method of positioning, which is based on using the model of single code differences for global navigation satellite system (GNSS) observations. In the research experiment, the authors used single-frequency code observations in the global positioning system (GPS)/global navigation satellite system (GLONASS) system from the on-board receiver Topcon HiperPro and the reference station REF1 (reference station for the airport military EPDE in Deblin in south-eastern Poland). The geodetic Topcon HiperPro receiver was installed in Cessna 172 plane in the aviation test. The paper presents the new methodology in the DGNSS solution in air navigation. The aircraft position was estimated using a “weighted mean” scheme for differential global positioning system and differential global navigation satellite system solution, respectively. The final resultant position of aircraft was compared with precise real-time kinematic – on the fly solution. Findings In the investigations it was specified that the average accuracy of positioning the aircraft Cessna 172 in the geocentric coordinates XYZ equals approximately: +0.03 ÷ +0.33 m along the x-axis, −0.02 ÷ +0.14 m along the y-axis and approximately +0.02 ÷ −0.15 m along the z-axis. Moreover, the root mean square errors determining the measure of the accuracy of positioning of the Cessna 172 for the DGNSS differential technique in the geocentric coordinates XYZ, are below 1.2 m. Research limitations/implications In research, the data from GNSS onboard receiver and also GNSS reference receiver are needed. In addition, the pseudo-range corrections from the base stations were applied in the observation model of the DGNSS solution. Practical implications The presented research method can be used in a ground based augmentation system (GBAS) augmentation system, whereas the GBAS system is still not applied in Polish aviation. Social implications The paper is destined for people who work in the area of aviation and air transport. Originality/value The study presents the DGNSS differential technique as a precise method for recovery of aircraft position in civil aviation and this method can be also used in the positioning of aircraft based on GPS and GLONASS code observations.

COMPARISON THE ACCURACY OF COMPUTING POINT COORDINATS BETWEEN DIFFERENT INSTRUMENTS AND APPLICATIONS OF GPS

The study was aimed to determine the coordinates of the points were measured by different ways and different instruments, the most precise way using the differential global positioning system (DGPS) that will be the reference measurements in comparison, less precise way using navigator GPS. Google earth (pro.), and the other applications of GPS mobile ( Samsung and I-phone). In this research (8 points) were chosen that are occasional in location. The comparison of the different observations can give us an idea of ​​the extent to which the accuracy of the observations differs from the different devices used in the observing, as well as through the knowledge of the best device and the best way to measure coordinates accurately to serve the desired purpose.

Age constraints on surface deformation recorded by fossil shorelines at Cape Range, Western Australia

Abstract Laterally continuous terraces along the western flank of Cape Range, Western Australia, record both past sea-level highstands and postdepositional vertical displacement. Four distinct fossil coral reef terraces extend nearly the entire length of the slowly uplifting anticlinal structure (∼100 km), enabling documentation of the timing and degree of deformation-induced elevation contamination of past sea-level estimates from fossil shorelines. Here, we present detailed elevations of the four terraces using differential global positioning system (DGPS) and airborne light detection and ranging (LiDAR) data sets, along with new ages for the three upper terraces. Geochemical dating using strontium isotope stratigraphy techniques revealed, from highest to lowest elevation: a late Miocene reef terrace, a late Pliocene shoreline, and a prominent mid-Pleistocene reef terrace (probably associated with the marine oxygen isotope stage 33–31 interglacial), along with a broad last interglacial (Eemian) reef terrace and lagoon, which terminate at the modern shoreline. Laterally variable elevation data integrated with newly defined ages for the terraces demonstrate a gradual and continuous relative deformation in the region that spans at least the last 6.5 m.y. and constrains the emergence of the Cape Range to sometime prior to the late Miocene. This data set also shows that the most recent interglacial shoreline has undergone <1.3 m of vertical warping, suggesting minimal deformation since deposition. By tracing relative uplift rates over multiple terraces for ∼100 km of coastline, we placed constraints on maximum relative sea level (RSL) for the older terraces. Most notably, we were able to place strict maximum RSL elevations of <+34 m on the Pliocene terrace and <+16.5 m on the mid-Pleistocene terrace, with probable RSL being somewhat lower.

Experimental Results and Posterior Cramér–Rao Bound Analysis of EKF-Based Radar SLAM With Odometer Bias Compensation

Radar mounted on a moving vehicle returns time-varying detections corresponding to unstable scattering points, unlike optical sensors, which produce relatively stable detections. We present an efficient extended Kalman filter-based simultaneous localization and mapping (EKF-SLAM) algorithm for radar, utilizing new techniques of clustering and sifting the time-varying detections. Velocity bias and yaw rate bias, which are inherent in any odometer are also estimated and compensated using the same EKF. For theoretical performance evaluation, the posterior Cramér-Rao bound (PCRB) for SLAM with odometer bias estimation is derived and compared with the root-mean-squared errors (RMSEs), with and without bias estimation. The simulation results show that the RMSE for SLAM with bias estimation is the closest to the PCRB. The proposed algorithm is also verified experimentally with field data. The comparison with the ground truth trajectory obtained from a differential global positioning system shows that the proposed algorithm yields an accurate trajectory estimate, even under large odometer bias. Also, the real-time capability of the proposed algorithm is verified.

Geospatial analysis to assess distribution patterns and predictive models for endangered plant species to support management decisions: a case study in the Balearic Islands

Species distribution modelling (SDM) has been used to support biodiversity management in recent years. However, the use of SDM at small scales with geolocation systems to obtain high-accuracy location data remains unexplored. In this study, we focused on Euphorbia fontqueriana, an endangered species to Mallorca (western Mediterranean basin), and we aimed to assess the spatial distribution patterns, and to generate a distribution map of the habitat suitability in a wider area. A differential GPS was used to geolocate all the ramets. We used the global Moran’s I index and local Getis Ord-Gi* method to assess the spatial patterns. We pre-selected derived topographic variables that were generated from LiDAR data (elevation, slope, northness and eastness), the connectivity index, normalised difference vegetation index, and soil type, as the environmental (predictor) variables. In addition, we ran the Maxent model using 1603 occurrence locations and seven environmental variables at a resolution of 2 × 2 m in grid size. The population consisted of 1625 ramets that were clustered (global Moran’s I index = 0.161, z score = 16.599, p value < 0.001) in several hotspots (i.e. areas with high plant density that were surrounded by areas with high plant densities). The Maxent model, which showed a good performance (AUC training score = 0.977), generated a habitat suitability map that displayed zones of high suitability in other areas away from the natural geographical area. Finally, we discuss the usefulness of this study to guide management purposes.