WGS 84 — Past, Present and Future

Slater, James A.; Malys, Stephen

doi:10.1007/978-3-662-03714-0_1

Cited by 29 publications

(12 citation statements)

References 3 publications

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“…PISM is defined on a regular Cartesian grid as shown in Fig. 1a, which is projected on a WGS84 ellipsoid (Slater and Malys, 1998) or related geometries like a perfect sphere. In this work PISM is used with a horizontal resolution of 16km × 16km with 80 vertical levels (Albrecht et al, 2020).…”

Section: Ice Sheet Model Pism and The Ice-shelf Cavity Module Picomentioning

confidence: 99%

Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO

Kreuzer¹,

Reese²,

Huiskamp³

et al. 2020

Preprint

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Abstract. The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high resolution configurations, limiting these studies to individual glaciers or regions over short time scales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM with the global ocean general circulation model MOM5 via the ice-shelf cavity module PICO. Since ice-shelf cavities are not resolved by MOM5, but parameterized with the box model PICO, the framework allows the ice sheet and ocean model to be run at resolution of 16 km and 3 degree, respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the entire Antarctic Ice Sheet and the Earth system over time spans on the order of centuries to millennia. In this study we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet model is calculated by PICO from modeled ocean temperatures and salinities at the depth of the continental shelf and, vice versa, the resulting mass and energy fluxes from the melting at the ice-ocean interface are transferred to the ocean model. Mass and energy fluxes are shown to be conserved to machine precision across the considered model domains. The implementation is computationally efficient as it introduces only minimal overhead. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions and time scales between the ice and ocean model in a generic way, and can thus be adopted to a wide range of model setups.

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Section: Ice Sheet Model Pism and The Ice-shelf Cavity Module Picomentioning

confidence: 99%

Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO

Kreuzer¹,

Reese²,

Huiskamp³

et al. 2020

Preprint

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“…Space geodesy (SLR, VLBI and GPS) can now provide an unprecedented high relative accuracy, even at a wide continental scale, but can only determine the geocentre to an accuracy of 1 m horizontally and 2 m vertically (see e.g. Slater & Malys 1998). Thus we do not expect that the accuracy of absolute displacements from space geodetic techniques will be better than 1 or 2 m (with respect to the geocentre), unless the geoid can be signi¢cantly improved in the absolute sense.…”

Section: Discussionmentioning

confidence: 99%

Invariant geodynamical information in geometric geodetic measurements

Xu¹,

Shinji

Fujii³

et al. 2000

Geophysical Journal International

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Summary Repeated geodetic measurements have been used to extract geodynamical quantities such as displacements, velocities of movement and crustal strains. Historical geodetic networks, especially those established before the space geodetic era, were, and still are, very important in providing a unique insight into the (local or regional) historical deformation state of the Earth. For the geodetic network without a tie to an external reference frame, free network adjustment methods have been widely applied to derive geodynamical quantities. Currently, it is commonly accepted that absolute displacements cannot be uniquely determined from triangulation/trilateration measurements, but relative displacements can be found uniquely if the geodetic network is geometrically overdetermined (see e.g. Segall & Matthews 1988). Strain tensors were derived using the coordinate method and were reported to be uniquely determined. We have carried out a theoretical analysis of invariant geodynamical information in geometric geodetic observations and concluded: (1) that relative displacements are not invariant quantities and thus cannot be uniquely determined from the geodetic network without a tie to an external reference frame; and (2) the components of the strain tensors are not all invariant and thus cannot individually be determined uniquely from the network. However, certain combinations of strain components are indeed invariant and can be uniquely determined from geometric geodetic measurements. The theory of invariant information is then applied to the analysis of the Tokai first‐order triangulation/trilateration network spanning an interval of more than 100 yr. The results show that the normal and principal strains are significantly affected by the unknown scaling biases and orientation differences; thus any attempt at geophysical interpretation of these quantities must be exercised with great care. If the scaling bias and the orientation difference are small, the shear strain is shown to be practically invariant. The invariant analysis of the Tokai network has also shown that a belt near Shizuoka has been significantly deformed in the past 100 yr; this has not been seen in any previous analysis of displacements and/or strains.

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“…Our indoor floor plan is visualized by a commercial toolbox called Mapbox, which can be found at https://www.mapbox.com/. In particular, we construct the indoor map in terms of the WGS-84 geodetic reference system [42] to remain consistent with the outdoor map offered by Mapbox. In the positioning mode, our HIPE application runs the Wi-Fi thread and PDR thread at the same time.…”

Section: Testbed Setup For Pssd Methodsmentioning

confidence: 99%

A Pairwise SSD Fingerprinting Method of Smartphone Indoor Localization for Enhanced Usability

et al. 2019

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Smartphone indoor localization has attracted considerable attention over the past decade because of the considerable business potential in terms of indoor navigation and location-based services. In particular, Wi-Fi RSS (received signal strength) fingerprinting for indoor localization has received significant attention in the industry, for its advantage of freely using off-the-shelf APs (access points). However, RSS measured by heterogeneous mobile devices is generally biased due to the variety of embedded hardware, leading to a systematical mismatch between online measures and the pre-established radio maps. Additionally, the fingerprinting method based on a single RSS measurement usually suffers from signal fluctuations due to environmental changes or human body blockage, leading to possible large localization errors. In this context, this study proposes a space-constrained pairwise signal strength differences (PSSD) strategy to improve Wi-Fi fingerprinting reliability, and mitigate the effect of hardware bias of different smartphone devices on positioning accuracy without requiring a calibration process. With the efforts of these two aspects, the proposed solution enhances the usability of Wi-Fi fingerprint positioning. The PSSD approach consists of two critical operations in constructing particular fingerprints. First, we construct the signal strength difference (SSD) radio map of the area of interest, which uses the RSS differences between APs to minimize the device-dependent effect. Then, the pairwise RSS fingerprints are constructed by leveraging the time-series RSS measurements and potential spatial topology of pedestrian locations of these measurement epochs, and consequently reducing possible large positioning errors. To verify the proposed PSSD method, we carry out extensive experiments with various Android smartphones in a campus building. In the case of heterogeneous devices, the experimental results demonstrate that PSSD fingerprinting achieves a mean error ∼20% less than conventional RSS fingerprinting. In addition, PSSD fingerprinting achieves a 90-percentile accuracy of no greater than 5.5 m across the tested heterogeneous smartphones

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WGS 84 — Past, Present and Future

Cited by 29 publications

References 3 publications

Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO

Coupling framework (1.0) for the ice sheet model PISM (1.1.1) and the ocean model MOM5 (5.1.0) via the ice-shelf cavity module PICO

Invariant geodynamical information in geometric geodetic measurements

A Pairwise SSD Fingerprinting Method of Smartphone Indoor Localization for Enhanced Usability

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