Reference Coordinate System Requirements for Geodesy and Ocean Dynamics

1975 ◽  
Vol 26 ◽  
pp. 93-114
Author(s):  
R. S. Mather
Keyword(s):  
Sea Level ◽  
Motion Vector ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
List Type ◽  
Type Number ◽  
Mean Sea Level ◽  
Crustal Motion ◽  
Four Dimensions

AbstractThe requirements for systems of reference in geodesy and ocean dynamics should be framed against the background of the distinct possibility of achieving in the foreseeable future measurements with a resolution of 1 part in 108. The current techniques promising this precision, with one exception, are based on observations to extraterrestrial sources/responders. The principal geodetic goals calling for such precision are, broadly stated, the determination of:1. Positions of stations in global tracking networks.2. Crustal motion.3. Polar motion.4. The radial component of instantaneous sea surface position from satellite altimetry for the estimation of phenomena related to ocean circulation.5. Earth model improvement.These goals cannot be achieved without the definition of adequate models for relating measurements from observing stations on Earth to extraterrestrial objects, possibly in an iterative manner in the first instance.While the specific choice of a system of geodetic reference is not critical for determinations of position in three dimensions, the maintenance of the continuity of geodetic concepts at the highest level of resolution in terms of four-dimensional considerations narrows the possible alternatives available.Criteria desirable in such a system of reference for observations of the highest precision made from the surface of a non-rigid Earth undergoing secular crustal motion are the following:1. These observations should be capable of direct relation to the system of reference in four dimensions.2. The crustal motion vector at a point should be defined in terms of the variations of the coordinatesof that pointwith time.3. Near-Earth orbital positions should have unambiguous relationships to the origin of ocean geoid determinations in four dimensions.4. Coordinates on the adopted system of reference should have relevance over an epoch of practical significance (e.g., one year).5. The scale for the space as obtained from the observations should not be influenced by factors other than the velocity of light and the adopted definition for the second.An important corollary is that only one point should be treated as “fixed” at the surface of the nonrigid Earth. Positional variations which have a periodic character, effective over an epoch of observation or less, are best treated as effects to be removed from observations by appropriate modeling. Reported secular changes in mean sea level require that the geoid be defined in relation to mean sea level in four dimensions for any determination of sea surface topography, thereby completing a unified system of reference which, would meet all the requirements of high-precision geodesy and ocean dynamics.

An alert in the psycho-social-health intervention. A graphic testimony of a real case with autism spectrum disorder

2011 ◽  
Vol 26 (S2) ◽  
pp. 758-758
Author(s):  
J.A. García ◽  
A.S. Raya ◽  
E.S. del Arco
Keyword(s):  
Autism Spectrum ◽  
Real Case ◽  
List Type ◽  
Type Number ◽  
High Functioning ◽  
The Family ◽  
Pertinent Information ◽  
New Challenges ◽  
Professional Intervention

The graphic papers of Pablo, 14 years, diagnosed of autism of high functioning, serve as a sign of alert when facing what underlies after the specializing professional intervention.A few letters, a few drawings, and a few words that show the powerlessness, the suffering and the absence of contextual specific adequacy.In this work we study, from the analysis of a real case, some excellent aspects in the psychosociosanitary attention, such as:-The need for compilation of pertinent information-The need for elimination of prejudices-The need for respect to the family-The need for specialized formation-The need for search of a shared communicative code-The need for search of strategies of social interaction-The need for empathy-The need for search of contextual specific adequacy-The need for rigorous rules in the physical containment.-The need of a turned over of adapted information-The need to respect the psychoevolutive situation of the patient-The need to give priority to the person on the illness.A testimony that should serve as a warning for those institutions, administrations and professionals who are thinking of having put all the resources to its scope.A testimony that should serve to contribute information and new challenges to those other professionals who do not stop their determination of conceptual and/or clinical anxious research.

Regional Mean Sea Surface Model over the Eastern Mediterranean Sea

2020 ◽  
Author(s):  
Milaa Murshan ◽  
Balaji Devaraju ◽  
Nagarajan Balasubramanium ◽  
Onkar Dikshit
Keyword(s):  
Time Series ◽  
Mediterranean Sea ◽  
Sea Level ◽  
Tide Gauge ◽  
Eastern Mediterranean ◽  
Sea Surface ◽  
Surface Model ◽  
Eastern Mediterranean Sea ◽  
Mean Sea Level ◽  
Mean Sea Surface

<p>The Mean Sea Level is not an equipotential surface because it is subject to several variations, e.g., the tides, currents, winds, etc. Mean Sea Level can be measured either by tide gauges near to coastlines relative to local datum or by satellite altimeter above the reference ellipsoid. From this observable quantity, one can derive a non-observable quantity at which the potential is constant called geoid and differs from mean sea surface by amount of ±1 m. This separation is called Sea Surface Topography. In this research, the data of nine altimetric Exact Repeat Missions (Envisat, ERS_1 of 35 days (phase C and G), ERS_2, GFO, Jason_1, Jason_2, Jason_3, Topex/Poseidon and SARAL) were used for computing the regional mean sea surface model over the eastern Mediterranean Sea. The data of all missions together span approximately 25 years from September -1992 to January-2017 and referenced to Topex ellipsoid.  Which is later transformed to WGS84 ellipsoid, as it is chosen to be a unified datum in this study. Prior to computing the altimetric MSS,  altimetric sea surface height measurements were validated  by comparing  time series of altimetric-MSL with mean sea level time series calculated from three in-situ tide gauge measurements.  The sea surface heights values of the derived MSS model is between 15.6 and 26.7 m. And the linear trend slope is between -3.02 to 6.53 mm/year.</p><p>Keywords: Mean Sea Level, Satellite Altimetry, Tide Gauge, Exact Repeat Missions</p>

Residual flows and elevations in the southern North Sea

1978 ◽  
Vol 359 (1697) ◽  
pp. 189-228 ◽  
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Close Agreement ◽  
Sea Surface ◽  
Residual Flow ◽  
Mean Sea Level ◽  
Surface Gradient ◽  
Residual Flows ◽  
Linearized Model ◽  
Good Agreement

The distribution of residual flow and the variation in mean sea level in the southern North Sea have been simulated by using a two-dimensional, vertically integrated, numerical model. The tidal residuals (i.e. the nonoscillatory tidal component) associated with the principal, M 2 , constituent were calculated from a fully nonlinear model and in specifying the boundary conditions for this model, the technique used by Proudman (1957) to accommodate residual terms was adopted. The residual flows computed for the M 2 constituent were found to account for approximately one half of the net computed residuals and the flow distribution produced by the model was shown to be in excellent agreement with both observations and previous calculations (Nihoul & Ronday 1975). A linearized model was used to simulate the effect of the major non-tidal forcing phenomena, namely wind, density and sea-surface gradients. The magnitudes of the friction coefficients in the linearized model were evaluated in terms of the M 2 tidal velocities. In simulating the response of the region to an imposed wind field, boundary conditions were calculated by reference to the method of characteristics. The relation, calculated from the model, relating the wind speed to the resulting flow and the elevation gradient in the Dover Strait, was found to be in close agreement with the corresponding relation deduced from observations by Bowden (1956). Similarly, the long-term variation in mean sea level due to wind forcing calculated by the model was found to be in good agreement with the variation computed from observations by Rossiter (1967). It was shown that, subject to the assumption of vertical homogeneity implicit in the model, the residual flows and elevations generated by horizontal density gradients were of only a minor significance. The net residuals were obtained by superimposing the separate components, namely those of tidal, wind and sea-surface gradient origin. The magnitude of the sea-surface gradient was determined by ensuring a best fit between the computed and recorded variations in mean sea level along the Continental coast. The difference in mean sea level between the Continental and English coasts was then calculated directly and was found to be in agreement with the earlier estimate by Cartwright & Crease (1963). In addition, the corresponding datum differences between the English and Continental levelling networks were computed and were found to be in good agreement with the value calculated by using the most recent British and French levellings of the tidal datums at Dover and Dunkirk. The magnitude of the net residual flow, computed in conjunction with these net sea-level gradients, was also in excellent agreement with the net residual derived from over 9 years of cross-Channel cable recordings (Alcock & Cartwright 1977). In addition, the net residual flow computed for wind-free conditions was in close agreement with the results from current meter recordings under similar conditions (Prandle & Harrison 1975). The distribution of this net residual flow was found to be consistent with previous observations and estimations based on ( a ) temperature and salinity distributions, ( b )current meter measurements, ( c ) sea-bed drifters, ( d )distribution of caesium 137, ( e ) movement of sand waves and ( f ) independent modelling studies. In conclusion, the results of this study provide a framework which both connects and relates the established studies of residuals in the Southern Bight. In addition, for the first time, a complete and comprehensive description is presented of the contribution of each of the major residual forcing phenomena.

Determination of the mean sea level at Deception and Livingston islands, Antarctica

2014 ◽  
Vol 27 (1) ◽  
pp. 101-102 ◽  
Author(s):  
Bismarck Jigena ◽  
Juan Vidal ◽  
Manuel Berrocoso
Keyword(s):  
Sea Level ◽  
Mean Sea Level ◽  
The Mean

Determination of mean sea-level at secondary stations

1926 ◽  
Vol s5-11 (64) ◽  
pp. 312-314 ◽  
Author(s):  
G. T. Rude
Keyword(s):  
Sea Level ◽  
Mean Sea Level

scholarly journals Determination of sea surface height from moving ships with dynamic corrections

2012 ◽  
Vol 2 (3) ◽  
pp. 172-187 ◽  
Author(s):  
J. Reinking ◽  
A. Härting ◽  
L. Bastos
Keyword(s):  
Satellite System ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Sea Surface Heights ◽  
Positioning Analysis ◽  
Remote Sensing Techniques ◽  
Global Navigation Satellite

AbstractWith the growing global efforts to estimate the influence of civilization on the climate change it would be desirable to survey sea surface heights (SSH) not only by remote sensing techniques like satellite altimetry or (GNSS) Global Navigation Satellite System reflectometry but also by direct and in-situ measurements in the open ocean. In recent years different groups attempted to determine SSH by ship-based GNSS observations. Due to recent advances in kinematic GNSS (PPP) Precise Point Positioning analysis it is already possible to derive GNSS antenna heights with a quality of a few centimeters. Therefore it is foreseeable that this technique will be used more intensively in the future, with obvious advantages in sea positioning. For the determination of actual SSH from GNSS-derived antenna heights aboard seagoing vessels some essential hydrostatic and hydrodynamic corrections must be considered in addition to ocean dynamics and related corrections. Systematic influences of ship dynamics were intensively analyzed and sophisticated techniques were developed at the Jade University during the last decades to precisely estimate mandatory corrections. In this paper we will describe the required analyses and demonstrate their application by presenting a case study from an experiment on a cruise vessel carried out in March 2011 in the Atlantic Ocean.

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