Differential GPS Research Articles

Ecological Impact Assessment of Permanent Site of Federal Polytechnic Oko Using Topographic Survey Method

Topographic survey based ecological impact assessment provides a mechanism for data integration, development, management and output presentation in a spatial environment. This research involved incorporating spatial data of all salient points at the Permanent Site of Federal Polytechnic, Oko, Anambra state to find a solution to the erosion menace. Differential Global Positioning System (DGPS) receiver was used to acquire spatial data of buildings, roads, spot height, drainages, catchment pits, etc. The topographic data were processed using ArcGIS software to analyze and produce the topographic maps. Presentations from the topographic survey revealed that the catchment topography runs between 160m – 198m height above the datum, the total area of the catchment area being 216320.653m2, perimeter is 2604.449m and the length of the mainstream is 1125.428m. Topographic maps of the area were used to assess the impact of the ecology on the area of study by analyzing the built up area, surface roughness, impervious and pervious surfaces. Hydraulic design of the drainage using best hydraulic section principle for most economic section to carry the flow was determined to solve the erosion problems in the catchment area. The flow rate obtained was 2.55m3/s and dimensions of the channel to be 1.1m depth and 2.2m width. The design of the selected structural members was done to mitigate against the erosion menace in the study area.

Geochemical and Documentary Topography of a Medieval Silver Valley: Detection of Workshops and Identification of Their Function

ABSTRACTThis paper presents the interdisciplinary investigation (archaeology, geochemistry, history) of a medieval silver and lead production site located in southern France, in the Minier valley (Occitanie, Aveyron, Le‐Viala‐du‐Tarn). In order to identify the production sites, in situ geochemical surveys were carried out using a portable X‐ray fluorescence spectrometer and differential GPS, guided on the analysis of medieval archival sources. The cartographic representation of the metal concentrations in the surface horizons shows significant enrichment of zinc and lead in the vicinity of the mines. This first type of enrichment makes it possible to highlight the activities of separation of sphalerite and silver‐bearing galena. The galena thus isolated on the hillsides is then transported to the vicinity of watercourses, where it is crushed, washed, and smelted. These secondary activities result in a last type of enrichment in which only lead is found in large quantities. The cross‐referencing of the information made it possible to overcome the challenges related to the location of the mineral processing workshops, which were often invisible on the surface. The medieval workshops have been located and a function suggested, outlining the first trends in the spatial and social division of labour and providing a solid corpus for future archaeological excavations. Finally, this study highlights the persistence of significant metal contamination in the soils of a rural valley and encourages the consideration of former mining areas when examining the environmental impact of metal production.

Quality Assessment of Multiple UAV-SfM DEMs Derived for Impact Assessment of a Co-Seismic Avalanche in the Himalayas

Combined with the structure from motion (SfM) technique, unmanned aerial vehicles (UAVs) are powerful tools for generating high-resolution digital elevation models (DEMs) for application in hazard assessments. During our field observations in October 2015 at Langtang Village, which was destroyed by the Gorkha earthquake in April 2015, three different UAVs with mounted cameras were operated to evaluate the volume of the avalanche deposit covering the village. This study evaluated the performance of DEMs created from the different cameras on board those UAVs. Multiple DEMs for the different cameras, including Sony-α7R (PA7), Ricoh-GR (XGR), and Canon-IXUS (EIX), were created using SfM software. All DEMs were compared with a base DEM created from differential global positioning system survey data, which was obtained simultaneously with the UAV campaigns. The results show that the elevation difference of PA7-, XGR-, and EIX-DEMs are within ±0.14 m; the standard deviations of elevation difference range from 0.33 to 0.40 m. Although there were slightly larger differences in elevation on the southwest-to-west sides of the XGR- and EIX-DEMs, which can be attributed mainly to the flight paths and ground control point network, our DEMs are still of high enough quality to be used in hazard assessments.

An Automatic Vehicle Navigation System Based on Filters Integrating Inertial Navigation and Global Positioning Systems

The key technologies for advanced autonomous vehicles include those relating to perception, decision making, and execution. Path-tracking control in autonomous vehicles is heavily dependent on their positioning system. Therefore, the development of low-cost and reliable positioning systems is crucial to improving perception and decision-making technologies for autonomous vehicles. Although the accuracy of the global positioning system (GPS) is extremely high, it is vulnerable to interference. Further, despite the low positioning accuracy of inertial navigation systems (INSs), their robustness is notably high. Therefore, an integrated navigation information method based on the Adaptive Particle Filter and the Iterative Kalman Filter (APF-IKF) was developed in this study. Firstly, an integrated navigation system model was established. Then, the IKF was adopted to estimate the speed, latitude and longitude errors of the INS. Thirdly, the newest estimated error results were introduced into the APF to optimize the distribution function, and the particle quality was improved. In this process, the APF can filter non-Gaussian noise, preliminarily estimate the error, optimize the result with the IKF and correct the output information of the INS with the final estimated error. Finally, by using differential GPS positioning as the benchmark, we built a real-vehicle test platform with a low-cost and low-precision GPS and inertial units and carried out a series of real-vehicle tests. The experimental results show that compared with the traditional KF method, APF-IKF can significantly improve the positioning accuracy and robustness of the system.

Performance Analysis of Internet-based DGPS and Commercial Satellite-based Augmentation System: A Case Study in Peninsular Malaysia

Global Navigation Satellite Systems (GNSS) has become an essential component in modern times for positioning, navigation, and timing. A fast-growing economic region in Malaysia required a GNSS-based augmentation positioning and navigation service. To improve navigation solution, several augmentation techniques exist, such as a differential Global Positioning System (DGPS) assisted by reference station, or augmentation service provided by commercial communication satellite. The DGPS correction is applied through a real-time communication medium and can be received at the user side by several communication methods including internet-based, and this method is favourable for land and near-coast areas. This case study aims to investigate the reliability of internet-based DGPS and SBAS along the Peninsular Malaysia. A test was conducted and data were collected over 15 hours at a rate of 1 Hz from the available GNSS satellite using a geodetic-grade receiver mounted on a moving vehicle. The obtained results showed that DGPS and SBAS perform better than the navigation solution with an accuracy of 1.536 m and 0.955 m respectively, compared to the navigation solution with an accuracy of 3.159 m. The limitations of both augmentation techniques were also analysed and discussed in this study.

Acquisition method based on differential global positioning system for land resource data

With the rapid development of the economy, many types of cultivated land have been occupied or transformed. Therefore, land-management departments need to grasp quickly the changes in land resources and utilise information technology to collect and process data on land resources. This can help with the scientific management of land resources. However, the traditional data collection strategy based on Global Positioning System (GPS)–Personal Digital Assistant (PDA) for land resource dynamic change data collection has noise issues. Therefore, a dynamic acquisition method of land resource data change based on differential GPS is proposed. In order to obtain the geometric data characteristics of land resources, the hierarchical division of land composition, the utilisation of land resource relationship and the combination of passive depth, combined with Kinect depth-acquisition equipment, the spatial geometric relationships of land resource data changes are obtained, and then differential GPS technology is used. The experimental results show that the proposed method can effectively overcome the noise problem of the GPS–PDA-based land resource dynamic change data collection method. It provides technical support for the planning and development of land-resource-management departments.

Climatically-driven development of late Quaternary fluvial geomorphology in the arid inland of Asia

The forcing mechanism behind river incision and terrace formation is one of hot topics in the study of fluvial geomorphology. This work focused on the late Quaternary alluvial sequence in the south piedmont of the Chinese Altay Shan in the arid inland of Asia. In order to reveal the mechanism controlling the development of late Quaternary fluvial features along the mountain front, we conducted detailed fluvial geomorphological investigations on eight rivers, including geomorphic mapping, optically stimulated luminescence (OSL) dating, and differential global position system (dGPS) surveying. By utilizing the Monte Carlo simulation with terrace data, the late Quaternary rates of river incision along the south piedmont of the Chinese Altay Shan were determined. The results show that (1) the terraces developed by the piedmont rivers are not more than four levels and the depth of river incision in the piedmont is only dozens of meters, with deeper valleys displayed by the western piedmont rivers; (2) terrace alluviums along the mountain front were accumulated during glacial stages, and the subsequent incision occurred during interglacial stages; (3) the rate of river incision was accelerated during the Holocene, when the regional climate was characterized by progressively increasing wetness. When combining with the regional tectonic setting, we propose that the climate could have played the key role in driving the alluvial accumulation and the subsequent incision in the south piedmont of the Chinese Altay Shan during the late Quaternary. Together with the similar observations from the northeastern margin of the Tibetan Plateau and the Tian Shan, we further propose that climatically-driven fluvial geomorphological development could be a common phenomenon during the late Quaternary in the arid interior of Asia.

Heuristic estimation of river bathymetry in braided streams using digital image processing

AbstractMeasurement of river bathymetry has been revolutionized by high‐resolution remote sensing that combines UAV platforms with SfM‐MVS photogrammetry. Mapping inundated and exposed areas simultaneously are possible using either two‐media refraction correction or some form of the Beer–Lambert Law to estimate water depths. If, as in turbid glacially‐fed braided streams, the bed is not visible then traditional survey techniques (e.g. differential GPS systems) are required. As an alternative, here we test whether the spatial distribution of water depths in a shallow braided stream can be modelled from basic planimetric data and used to estimate inundated zone bathymetry. We develop heuristic rules using; (1) distance from the nearest river bank; (2) total inundated width along a line tangential to the local flow direction; (3) local curvature magnitude and direction; and distance from the nearest flow (4) divergence and (5) convergence regions. We parameterize them using a sample of measured water depths in stepwise multiple linear regressions and validate them using independent data. Resulting water depth distribution maps explain between 50% and 60% of the measured water depth spatial variability when compared to independent data. After incorporating modelled water depths into digital elevation models (DEMs) of exposed areas, we show that the developed method is suitable for volumetric change calculations in both dry and inundated areas.

Comprehensive geospatial mapping and monitoring of an eastern coalfield in India

Geospatial mapping and monitoring are crucial for designing slopes in opencast mining, as failure can result in significant economic and life loss. To overcome these issues, the present investigation evaluated the Digital Elevation Model (DEM) generated using high resolution Cartosat-1 satellite imagery. Simultaneously, mapping of shaded relief map, aspect map and slope maps was done for the monitoring of Shatabdi opencast coal mine of Jharia region, an eastern coalfield region of India. Shaded relief map was categorized in to low, moderate and high categories and maximum area was covered by moderate to high shades. The constructed aspect map encompasses the range between 0 and 360 degrees of direction, with categorization and representation through distinct colors. The slope map was classified into various categories based on degrees of slope, including very gentle, gentle, moderate, moderately steep, steep, and very steep slopes. The maps were ground validated using Differential Global Positioning System (DGPS) collected data points by field visit in the region. For opencast mines to operate safely and profitably, slope stability in different stages of mining must be mapped and monitored. The study synthesizes data from diverse sources, highlighting the role of geospatial technology in addressing multiple research gaps within the mining industries prior to leveraging Cartosat-1 satellite data. Slope mapping and monitoring of coalfield regions are crucial to reducing construction costs, mitigation of natural hazard risks like flooding and landslides, and effective conservation of natural resources such as soils, vegetation, and water systems. The present study benefits policymakers, environmental planners and government in formulating policies to ensure safety, reliability, and enhance the economic growth of workers and the country.

Surface deformation monitoring of Raniganj coalfield, India, using advanced InSAR and DGPS

The Raniganj coalfield, which is the oldest coal mine in India, is susceptible to ground subsidence. For the purpose of detecting surface deformation, this work makes use of field surveys, interferometric synthetic aperture radar (InSAR), and Differential GPS (DGPS). The study utilised Sentinel-1 InSAR data spanning from 2017 to 2023. PS-InSAR was used for both ascending and descending datasets, while SBAS-InSAR was used for descending datasets alone. Records show a maximum subsidence rate of −21.18 mm/year. Three surface deformation maps were generated from time-series assessments of individual locations, revealing regions undergoing significant changes. Known mining collapse locations and continuing deformation zones were designated with four differential GPS stations. By analysing the DGPS data with the GAMIT/GLOBK software, we were able to measure surfaces that were undergoing rapid deformation. Using Google Earth Engine (GEE), we generated thermal maps to delve deeper into the coal fire activity. We found coal bed methane (CBM) mining causing substantial subsidence in Kataberia and the surrounding areas. Shyamsundarpur and New Kenda are impacted by mining voids and coal fire-induced subsidence, respectively. The results of this study give the Raniganj region’s decision-making procedures more credibility in terms of minimising and controlling geological dangers.

Bathymetric survey and volumetric analysis of Bakolori dam reservoir North West Nigeria

Many approaches have been devised for measuring water depth in bathymetric surveys, which are used to assess sediment deposited directly in lakes and reservoirs. This technique is mostly used to calculate the reservoir's capacity and the amount of sedimentation that occurs there. The results of the volumetric analysis and bathymetric survey of the Bakolori Dam reservoir, which is situated in Northwestern Nigeria, are presented in this work. During this investigation, the differential Global Positioning System receiver (GPS), automatic level measuring tool, echo-sounder, and engine boat were utilized. ArcGis 10.0 was used to analyze the acquired data. In order to evaluate the reservoir capacity loss during the Bakolori reservoir's operating period as of 1983, the designed computed reservoir capacity was compared with the current bathymetry survey. At a spillway crest elevation of 334 meters above mean sea level (amsl), the reservoir's initial capacity is reported as 430 million cubic meters (MCM). However, the capacity has since been revised to 291 meters at the same level, with a volume change of 139,269,495 m3. As a result, the reservoir's volume changed by approximately 139 MCM during a thirty-five (35) year period of service, representing a loss of storage capacity, while the annual siltation rate was around 3,979,128 m3/a. This indicated that 33% of the reservoir's storage capacity had silted up. This is demonstrated by the aquatic weeds that have grown to a height of 334.21 meters on the lake's surface, rising from the lakebed. Therefore, to prevent total siltation, the dam reservoir needs to be adequately dredged.

The growth and emergence of potentially dangerous glacier lakes in Astore Basin, Western Himalaya during 1993–2021

The recent retreat of glaciers in High Mountain Asia is a major issue for downstream communities. Similarly, glaciers in the Astore Basin are melting, causing glacial lakes to expand faster, new lakes to form, and increasing the risk of glacial lakes outburst floods (GLOFs). The present study uses Landsat data from 1993 to 2021 to explore seasonal and decadal changes in glacier lakes, which are validated using an in situ differential Global Positioning System (dGPS). During the ablation period (June - October) of 2021, we observed a five-fold increase (18 to 100) in the number of glacier lakes, as well as a six-fold increase (0.62 to 3.86 km2) in lakes larger than 0.01 km2. Over the last decade, from 2011 to 2020, the number of potentially dangerous glacial lakes (PDGLs) has doubled. GLOF risk must be reduced through continual monitoring of these lakes. Prioritizing the deployment of GLOF monitoring and early warning systems, as well as sustainable water management practices, is critical for mitigation and adaptation measures in mountainous regions.

Spatial Analysis of Response Initiative to the outbreak of Diphtheria in Ojo Local Government Area of Lagos State, Nigeria.

In the Africa Continent, diphtheria remains a pressing public health concern. Despite advancements in healthcare infrastructure and vaccination efforts, several countries continue to report cases and outbreaks, indicating ongoing transmission of the disease. This research aimed at utilizing GIS application in diphtheria outbreak in the Ojo Local Government Area (LGA) of Lagos State, Nigeria, with the following objectives: (i) obtain the spatial distribution pattern of the spread of diphtheria outbreak. (ii) determine the area requiring immediate attention and response in the study area. (iii) showcase areas that are vulnerable within the study area. In the pursuance of this both primary data, including geographical coordinates of confirmed diphtheria cases, and secondary data such as recorded cases, population density, vaccination coverage, and transportation networks, the research utilizes ArcGIS for visualization and analysis, Differential Global Positioning System (DGPS) receivers ensured accurate spatial data collection, supplemented by ground truthing of secondary data. The result revealed significant clusters of diphtheria cases in Akesan-Obadore and Ijegun, indicating a higher concentration of infections. The study applied average nearest neighbor analysis, which indicated a dispersed pattern of outbreaks within the LGA. Furthermore, a risk assessment using Analytic Hierarchical Process (AHP), in identifying the southern parts and Iba ward of Ojo LGA as areas with highest risk. The study recommends to the Lagos State Government to enhance vaccination efforts and improve sanitation infrastructure in these high-risk areas to mitigate the spread of diphtheria.

Contemporary movement of rock glaciers in the La Sal and Uinta Mountains, Utah, USA

Rock glaciers are common landforms in mountainous areas of the western US. The motion of active rock glaciers is a key indicator of ice content, offering connections to climate and hydrologic systems. Here, we quantified the movement of six rock glaciers in the La Sal and Uinta Mountains of Utah through repeat differential GPS surveying. Networks of 10–41 points on each rock glacier were surveyed in September 2021; July 2022; September 2022; and July 2023. We found that all features are moving with average annual rates of motion from 1.5 ± 0.8 to 18.5 ± 7.5 cm/yr. Rock glaciers move up to 3× faster in the summer than in the winter, and rates of motion were greater in 2023 after a winter with above-average snowfall, emphasizing the role of liquid water availability. Velocities of individual points in the winter of 2021–22 are positively correlated with velocities during the winter of 2022–23, suggesting that spatial variability of motion is not stochastic, but rather reflects internal properties of each rock glacier. Bottom temperature of snow measurements during winter, and the temperature of springs discharging water in summer, suggest that these rock glaciers contain modern permafrost. Radiocarbon data document advance of one rock glacier during the Little Ice Age. Our GPS dataset reveals complicated patterns of rock glacier movement, and the network of survey points we established will be a valuable baseline for detecting future cryosphere change in these mountains.

Real-time mapping of crop canopy temperature using a wireless network of infrared thermometers on a central pivot

Efficient irrigation is essential for sustainable food production and regional water security. Temperature measurements provide information about crop water status, which allows the estimation of water needs and precise irrigation scheduling. This paper proposes a technology for agricultural irrigation management that combines cost-effective implementation with the ability to map crop canopy temperatures using a wireless network of infrared thermometers on a center pivot. The technology integrates Wireless Sensor Networks (WSN) with scalability options, IoT capabilities, and web data availability, enabling precise plant water stress quantification based on canopy temperature and soil water content. It facilitates real-time irrigation prescriptions while the center pivot is in motion, with canopy temperature sensors providing accurate readings of +/- 0.5 °C without additional calibration. Nonlinear Autoregressive Network with Exogenous Inputs (NARX) and Long Short-Term Memory (LSTM) neural network models were trained to predict irrigation prescriptions, achieving Root Mean Squared Error (RMSE < 4.18 mm) and correlation coefficient (r^2 > 0.82). This technology will allow the definition of real-time and site-specific prescriptions for variable-rate irrigation systems using infrared temperature sensors. Future work includes exploring LoRaWAN technologies, implementing a Differential Global Positioning System (DGPS), improving spatial resolution with data fusion algorithms, refining irrigation prescription models, reducing sensor costs and developing models considering soil and crop effects.

Making Different Topographic Maps with the Surfer Software Package

The main objective of this study is to describe the preparation of topographic maps using the Surfer software. A total of 159 regularly distributed Ground Control Points (GCPs) were collected with the use of the Differential Global Positioning System (DGPS). Seven methods (Contour Map, Post Map, 3D Surface Map, 3D Wireframe Maps, Grid Vector-1 Map, Color Relief Map, and Shaded Relief Maps) at the Surfer environment were used to prepare the topographic maps at the Mukhtar Village near the Al-Fallujah City. Contour lines with other features were superimposed on the DEM layer, which refers to the topography of the terrain inside this study area. The accuracy of the database's results was estimated, essential maps were given, and the results were efficient and effective. The most appropriate method to represent topographic maps was proposed, each of these techniques has been enough to provide us with a general understanding of the subject area.

Comparative Analysis of Smartphones and Survey-Grade GNSS Receivers for Parcel Boundary Determination

This paper advances the existing body of knowledge on the suitability of the accuracy derivable from the use of smartphones for cadastral mapping. Zenvus App software was installed on two smartphones of a different make. A set of dual-frequency GPS Promark 3 receivers and two different smartphones of different makes were used for data acquisition. Observations were carried out at the boundaries of ten parcels of land, comprising 46 boundary points. The coordinates of these points were obtained using Differential Global Positioning System (DGPS) observation in static mode and two Android smartphones (the Samsung A70 and the Tecno Spark 3 Pro). Mean score, root mean square error, and one-way analysis of variance were used to show significant differences in the equipment used. Overall, both the accuracy (mean) and precision (RMSE) were lower than those obtained by Differential GPS. A one-way analysis of variance (ANOVA) was calculated on the values of both X and Y. For X, the analysis was not significant; F (1, 45) = 0.88, p = 0.419 and for Y, the analysis was also not significant; F (1, 45) = 0.97, p = 0.383. The total RMSE shows that the coordinates of points as obtained by the Samsung smartphone (3.368) were more precise than those obtained by Tecno (4.041). However, the two smartphones (Tecno and Samsung) were less accurate than differential GPS. This implies that there is a 95% chance that the errors in the estimates are less than 6.993m (for Tecno) and 5.848m (for Samsung), respectively. The variation in the observations obtainable with smartphones affects both linear and polygon estimates. The study concluded that the magnitude of these errors is significant in cadastral survey practices and hence not suitable for use. It is recommended that further studies be carried out on the use of the Zenvus app on centimeter grade smartphones; probably this could yield a better result suitable for cadastral mapping.

Hydrodynamic modelling to assess habitat suitability of the Ganga River dolphins

AbstractThe Ganga River hosts a metapopulation of endangered aquatic species. This study uses a hydrodynamic model (HEC‐RAS) to assess the habitat suitability of the Ganga River dolphins (GRDs) in a small reach (7.5 km) of the Ganga River at the upstream of Narora barrage in varying flow. We use Lidar points clouds to generate topography, Acoustic Doppler Current Profiler (ADCP), and differential GPS (DGPS) to measure channel bathymetry and streamwise water surface slope. Further, the water level data from satellite altimeter is used to calibrate the model and discharge measured in field to validate the model output. We found that in the high flow period, the required flow depth for dolphin habitat is available throughout in the study reach. However, in the lean flow, the required flow depth and velocity are available only in some patches. The methodology developed here would be very useful in monitoring hydraulic habitat suitability of aquatic species in ungauged rivers.

Analysis of the Teaching Path of Animation Film Majors Integrating Digital Visual Space in the Context of Digital Media Art

Abstract In this study, we first adopt the dynamic stereo vision spatial coordinate measurement method of non-zoom cameras, establish a coordinate measurement model based on differential GPS, and study the application of the spatial coordinates of dynamic stereo digital vision systems in animation design. Secondly, the internal and external parameters of the camera are defined as the static error of the dynamic stereo vision system so as to provide an easy and quick-to-use design tool for the teaching of animation film majors. Finally, a test sequence animation sample set is used to verify the teaching effect of digital visual space based on animation design. The results show that in the multi-comparison test of animation quality against pixel bit rate, the animation design samples were found to have frame rates in the range of 5-30 Fps. And under the condition of having extra bandwidth, the animation feature learning evaluation dimension is 2589, and increasing the animation visual frame rate can improve the output picture quality of animation more effectively. It shows that the integration of digital visual space in the context of digital media art can allow students to have enough project sources for learning and practicing so as to improve their professional ability.

Variability of quaternary marine terraces and uplift rates in the Andean coastal zone at 23°S

During the Quaternary most of the coastal areas along the Andes were uplifted due to subduction related processes. At 23°S, along the Mejillones Peninsula and the shoreline of the Coastal Cordillera, there is an abundance of Quaternary marine terraces, coastal cliffs, eroded dikes, alluvial fans, and fault scarps which preserve evidence of this uplift. The hyper-arid conditions have minimised subaerial erosion to the extent that the Quaternary marine terraces (QMT) can be carefully studied to understand the amount of permanent deformation in the forearc and the variability of uplift rates along the coast. A morpho-metric analysis using remotely sensed imagery from ALOS-PALSAR, drone survey and local differential GPS data allowed us to define the best-preserved QMT sequences and the elevation at which they were found with respect to the modern mean sea level. We propose a correlation between the individual paleo-shorelines of each marine terrace with a Quaternary Marine Isotope Stage (MIS). We determined two representative areas with well-preserved marine terraces: Morro Mejillones, in the western zone of the Mejillones Peninsula (∼12 × 10 km2) and the combined Hornitos – Punta Chacaya zone (∼16 × 7 km2), in the northern part of the Mejillones Bay. Within these areas we identified 12 QMT's in Morro Mejillones with estimated uplift rates between 0.31 and 0.76 m/ka over the last 600 ka, 3 QMT's In Hornitos with uplift rates between 0.28 and 0.4 m/ka over the last 220 ka, and 4 QMT's in Punta Chacaya with uplift rates between 0.25 and 0.39 m/ka over the last 330 ka. We link differences in uplift rates as related primarily to the distance from the coastal zone to the subduction trench and, locally, to their variable location with respect to faults active during the Quaternary.