Assessment of Hydrographic Data Uncertainty for Seamless Reference Surface

2006 ◽  
Vol 59 (2) ◽  
pp. 213-220
Author(s):  
Ahmed El-Rabbany
Keyword(s):  
Covariance Matrix ◽  
Data Uncertainty ◽  
Topographic Maps ◽  
Reference Surface ◽  
Hydrographic Data ◽  
Measuring Techniques ◽  
The World ◽  
Geodetic Technique ◽  
Lead Line ◽  
Hydrographic Surveying

The development of a seamless vertical reference surface is accompanied by a number of challenges pertinent to the availability, volume and uncertainty of bathymetric and topographic data. Data uncertainty, which is by far the most difficult to deal with, is attributed to various sources of errors including those of geodetic and hydrographic origin. The uncertainties in the geodetic measurements originate mainly from the limitations in the geodetic technique employed, i.e. terrestrial or space. Old nautical charts and topographic maps were based on terrestrial techniques, which are far less accurate than modern space techniques. In addition, the distribution of the positioning uncertainty is not expected to follow a consistent pattern across the chart (map). This is mainly due to the inconsistent datum distortion as well as the discrepancies in the measuring techniques in the subsequent chart (map) versions. The existing paper (and digitized) charts in many areas of the world were also based on old hydrographic surveying methods, for example the lead-line, which are far less accurate than modern techniques such as multibeam echo-sounding surveys. This creates inconsistent depth uncertainty across the chart. As uncertainties are propagated into the estimated transformation parameters, estimated positions and their covariance matrix, it is of utmost importance that they are properly modelled. This paper addresses the issue of uncertainty in hydrographic data and suggests ways to account for it.

scholarly journals The Thinness of the Ocean in S–Θ–p Space and the Implications for Mean Diapycnal Advection

2007 ◽  
Vol 37 (6) ◽  
pp. 1714-1732 ◽  
Author(s):  
Trevor J. McDougall ◽  
David R. Jackett
Keyword(s):  
Dimensional Space ◽  
World Ocean ◽  
Three Dimensional ◽  
Small Scale ◽  
Lateral Motion ◽  
Hydrographic Data ◽  
Mixing Processes ◽  
The World ◽  
The Mean ◽  
Three Dimensional Space

Abstract It is shown that the ocean’s hydrography occupies little volume in the three-dimensional space defined by salinity–temperature–pressure (S–Θ–p), and the implications of this observation for the mean vertical transport across density surfaces are discussed. Although ocean data have frequently been analyzed in the two-dimensional temperature–salinity (S–Θ) diagram where casts of hydrographic data are often locally tight in S–Θ space, the relatively empty nature of the World Ocean in the three-dimensional S–Θ–p space seems not to have received attention. The World Ocean’s data lie close to a single surface in this three-dimensional space, and it is shown that this explains the known smallness of the ambiguity in defining neutral surfaces. The ill-defined nature of neutral surfaces means that lateral motion along neutral trajectories leads to mean vertical advection through density surfaces, even in the absence of small-scale mixing processes. The situation in which the ocean’s hydrography occupies a large volume in S–Θ–p space is also considered, and it is suggested that the consequent vertical diapycnal advection would be sufficiently large that the ocean would not be steady.

scholarly journals Radon in the Dwellings: Causes and Prevention

2017 ◽  
Vol 3 (1) ◽  
pp. 1-5
Author(s):  
M Shakir Khan
Keyword(s):  
National Survey ◽  
Public Awareness ◽  
Developed Countries ◽  
Health Hazards ◽  
Inert Gas ◽  
Permissible Level ◽  
Naturally Occurring ◽  
Measuring Techniques ◽  
The World

The problem of radon in dwellings gained importance in 1984 after an incidence in Pennsylvania, USA; thereafter several measuring techniques have been developed and national survey programs were started throughout the world for monitoring radon levels by government authorities. The lots of work have done by researchers in this field throughout the world. Several developed countries have given guidelines for initiating action to reduce radon levels if found beyond permissible level. The main aim of this article to provide public awareness about the health hazards posed by radon, which is naturally occurring invisible inert gas in the dwellings that is not be detected by human senses.

Analysis of Tire Performance on Sand

1995 ◽  
Vol 23 (1) ◽  
pp. 52-67 ◽  
Author(s):  
H. Ataka ◽  
F. Yamashita
Keyword(s):  
Empirical Equation ◽  
Theoretical Equation ◽  
Shearing Stress ◽  
Propulsive Force ◽  
Breaking Force ◽  
Measuring Techniques ◽  
The World ◽  
Precise Prediction ◽  
The Difference

Abstract Recently, vehicles on sand have been operated at higher speeds with diversified usage, and requests for the development of radial tires, applicable to both pavements and sandy areas have emerged. Although a large number of studies and analyses of tire performance on paved surfaces have been reported, few reports are available for tire performance on sandy surfaces. This study deals with the behavior of radial tires on the sand. A simple theoretical equation was derived in which the sand traction performance could be expressed as the difference between the propulsive force and the driving resistance on sand. The theoretical equation was found to be highly related to the empirical equation derived from previous work. Sand samples from typical deserts were used for analyses of shearing stress and compressive breaking force of sand through unique measuring techniques, resulting in modification of the theoretical equation to give more precise prediction of the tire performance on sand for most areas in the world.

scholarly journals The geoid or quasigeoid – which reference surface should be preferred for a national height system?

2013 ◽  
Vol 3 (2) ◽  
pp. 103-109 ◽  
Author(s):  
L. E. Sjöberg
Keyword(s):  
Density Distribution ◽  
Analytical Continuation ◽  
Reference Surface ◽  
Numerical Instability ◽  
Convergence Problem ◽  
The World ◽  
Height System ◽  
Normal Heights ◽  
Integration Problem ◽  
Stokes Formula

Abstract Most European states use M. S. Molodensky’s concept of normal heights for their height systems with a quasigeoid model as the reference surface, while the rest of the world rely on orthometric heights with the geoid as the zero-level. Considering the advances in data caption and theory for geoid and quasigeoid determinations, the question is which system is the best choice for the future. It is reasonable to assume that the latter concept, in contrast to the former, will always suffer from some uncertainty in the topographic density distribution, while Molodensky’s approach to quasigeoid determination has a convergence problem. On the contrary, geoid and quasigeoid models computed by analytical continuation (e.g., rcr technique or KTH method) have no integration problem, and the quasigeoid can always be determined at least as accurate as the geoid. As the numerical instability of the analytical continuation is better controlled in the KTH method vs. the rcr method, we propose that any future height system be based on normal heights with a quasigeoid model computed similar to or directly based on the KTH method (Least squares modification of Stokes formula with additive corrections).

The Evolution of the English Nautical Chart

1952 ◽  
Vol 5 (4) ◽  
pp. 362-374
Author(s):  
A. H. W. Robinson
Keyword(s):  
Seventeenth Century ◽  
Present State ◽  
Nautical Chart ◽  
The Past ◽  
The World ◽  
Short Span ◽  
The Many ◽  
National Defence ◽  
Hydrographic Surveying

In a previous contribution Professor E. G. R. Taylor has reviewed the development of the sea chart up to 1600, the year in which Edward Wright published his celebrated chart of the world on Mercator's projection. Wright's chart represents one of many minor incursions on the part of English cartographers into the field of nautical cartography, which at that time and for the next hundred years was dominated by the flourishing Dutch school of hydrography. It was not until the latter began to decline towards the end of the seventeenth century that the English cartographer really came into his own and began to produce charts to assist the navigator. Thus the evolution of the English nautical chart to its present state of development covers a relatively short span when measured against the whole background of maritime enterprise and endeavour.The development over the past two hundred and fifty years has been sporadic rather than continuous, being characterized by sudden advances followed by long intervals of consolidation. Factors such as the needs of national defence, the invention of navigational instruments and advances in hydrographic surveying technique, have at various times acted as stimulants to chart evolution. Throughout the period under review responsibility for supplying the navigator with accurate charts has gradually passed from the many private publishing firms to a specially created national department.

scholarly journals The Usage of Probability Theory Concepts for Analysing Big Data Uncertainty Reasoning

2020 ◽  
pp. 151-155
Keyword(s):  
Probability Theory ◽  
Big Data ◽  
Data Use ◽  
Data Uncertainty ◽  
Complex World ◽  
Common Occurrence ◽  
Uncertainty Reasoning ◽  
Partial Observability ◽  
Degree Of Belief ◽  
The World

Partial observability, nondeterminism or a combination of the two develop the problem of uncertainty a common occurrence in big data. An agent is needed to handle this uncertainty. This paper aims to see how an agent can tame uncertainty with the degree of belief and to design an agent program that implements the agent function, the mapping from percepts to actions, especially in the field of big data where volumes of data needs to be handled. The agent program more often takes the current percept as input from the sensors and return an action. Uncertainty arises because of ignorance or volumes of data; The agent’s lack to express the truth of the event in the sentence due to uncertainty that prevails, which can be expressed using probability. Probabilities summarises the agent’s belief relative to the evidence and probability distribution is used to specify the probability that exist in assigning to any random variables. Partial observability of the world brings in unobserved aspects, these can be resolved by estimating the values using probability, that help better agent decision in any field including big data. The agent program come into being through learning methods. An agent is designed to form representations of a complex world, the world with huge voluminous data, use a process of inference to derive new representations about the world, and use these new representations to deduce what to do.

scholarly journals Towards sustainable topographic mapping

2019 ◽  
Vol 1 ◽  
pp. 1-1
Author(s):  
Haico van der Vegt ◽  
Ton van Helvert ◽  
Paula Dijkstra
Keyword(s):  
Spatial Data ◽  
Development Stage ◽  
Topographic Maps ◽  
Topographic Mapping ◽  
Topographic Map ◽  
Sources Of Information ◽  
The Sustainable Development ◽  
Aerial Photos ◽  
The World ◽  
The Government

<p><strong>Abstract.</strong> “Everything happens somewhere”, a popular phrase nowadays to emphasize the importance of good and reliable geographic information. National Spatial Data Infrastructures (NSDI) are popping up in many countries in the world as governments realize that a wealth of geo-data is produced, but that this data is not known or available to other organizations. An NSDI channels this information to the users. Availability of geo-information and efficiency in the production are the key drivers.</p><p>Another big driver is the Sustainable Development Goals (SDG). To monitor the development of the progress of the SDG’s, a wealth of statistical information on economic, social and environmental phenomena is collected. All this data is referring to a specific place on earth. Therefore, good and reliable geo-information is critical for the development of the SDG’s of a country.</p><p>Topographic maps describe the land that belongs to a country, its sovereign territory. But they are also used for orientation, for the defense of your country, as a time stamp of how your country looks like at a specific moment in time, and many other applications. Topographic maps are therefore an indispensable asset in an NSDI. They link thematic information of any kind to a specific location. It is this location that is the linking pin to many other sources of information.</p><p>However, the reality of today is that many developing countries lack any up-to-date topographic maps. They have to rely on old maps, often produced more than 40 years ago; there is no money or, more importantly, no expertise available to update these maps. In other cases, they rely on online mapping sources like Google Maps, OpenStreetMap, etc. These are good, but consistency in quality is an issue.</p><p>Some countries already have topographic maps, but these date back from colonial times, and were not updated ever since. Others produce specific map series but are depending on the availability of reliable source material, like aerial photos and satellite imagery, purchased by the government. Or in some cases they have to organize partnerships with other national institutions to be able to purchase the necessary photo’s or imagery. Regular maintenance of these maps is then often a real issue.</p><p>In general, every country has its own development stage, but when it comes to topographic mapping, it can be classified into 4 stages:</p><p>1. No topographic map available</p><p>2. Out of date analogue topographic map available</p><p>3. Digital, but out of date topographic map available</p><p>4. Digital and recent topographic map available</p><p>This paper describes these different stages of official map production that exist in countries around the world, each stage with its own characteristics, timeframe, roadmap and needs. It is not focusing on the technology but concentrates on the institutional aspects of topographic map production and what could be done to develop the production processes into sustainable work procedures.</p>

The Canadian Geodetic Vertical Datum of 2013 (CGVD2013)

GEOMATICA ◽  
2016 ◽  
Vol 70 (1) ◽  
pp. 9-19 ◽  
Author(s):  
Marc Véronneau ◽  
Jianliang Huang
Keyword(s):  
Global Navigation Satellite System ◽  
Satellite System ◽  
Navigation Satellite ◽  
Gravimetric Geoid ◽  
Reference Surface ◽  
Geoid Model ◽  
Gnss Positioning ◽  
Vertical Datum ◽  
The World ◽  
Global Navigation Satellite

The Canadian Geodetic Vertical Datum of 2013 (CGVD2013) is the first major update to the vertical datum in Canada in almost 100 years. Canada is not only moving to a new vertical datum, but it is also using a modernized approach to realize it. The modernization of the height reference system is necessary to make it compatible with Global Navigation Satellite System (GNSS), which is commonly used for positioning by a growing number of users across Canada and the world. The geodetic levelling technique, which established a nation-wide network of benchmarks with known elevations, is replaced by a geoid model that describes the vertical datum with respect to an ellipsoid, which is the reference surface for GNSS positioning. Technically, height modernization replaces the need for the maintenance of benchmarks, as users can now install their own markers at more convenient locations using GNSS. The current geoid model for CGVD2013 is the Canadian Gravimetric Geoid 2013 (CGG2013).

scholarly journals Temperature Inversions in the Subarctic North Pacific

2005 ◽  
Vol 35 (12) ◽  
pp. 2444-2456 ◽  
Author(s):  
Hiromichi Ueno ◽  
Ichiro Yasuda
Keyword(s):  
North Pacific ◽  
North Pacific Ocean ◽  
World Ocean ◽  
Gulf Of Alaska ◽  
Tidal Mixing ◽  
Large Temperature ◽  
Hydrographic Data ◽  
Subarctic North Pacific ◽  
The World ◽  
Temperature Inversions

Abstract Hydrographic data from the World Ocean Database 2001 and Argo profiling floats were analyzed to study temperature inversions in the subarctic North Pacific Ocean. The frequency distribution of temperature inversions [F(t-inv)] at a resolution of 1° (latitude) × 3° (longitude) was calculated. Temperature inversions seldom occurred around 50°N in the eastern subarctic North Pacific but were more common in the northern Gulf of Alaska and the southeastern subarctic North Pacific (42°–48°N, 140°–170°W). Large temperature inversions occurred throughout the year in the western and central subarctic North Pacific (north of 42°N and west of 180°) except near the Aleutian and Kuril Islands. Near those islands, F(t-inv) was characterized by pronounced seasonal variations forced by surface heating/cooling and strong tidal mixing.

scholarly journals The Treasure Map of the citizen childhood

2021 ◽  
Vol 4 ◽  
pp. 1-8
Author(s):  
Jasmine Desclaux-Salachas
Keyword(s):  
Civil Engineering ◽  
Public Library ◽  
Human Freedom ◽  
Topographic Maps ◽  
Manufacturing Processes ◽  
Data Bases ◽  
The Public ◽  
The World ◽  
Scientific Team

Abstract. We are cartographers, trained and dedicated to our respective institutions around the world. Our cartographic works are gradually being developed, combining our multiple professional scientific and artistic skills, in the service of citizen information through the production of our maps. The performance of our works, submitted to the confidentiality of informations and data bases we process, remains invisible to public. In our complex job, confidentiality is a rule we first respect. We don’t usually explain our sophisticated manufacturing processes. Only our final result counts: THE MAP, completed, faithful to its project, editable, interpretable and memorizable at a first glance of its users.Among the Ecomuseum scientific team that was created in Battir, Palestine, after 2003, there was no cartographer. The team of young Palestinian professionals in architecture and civil engineering, just graduated, was armed with the rigour of their newly acquired knowledge, armed with their human freedom and citizen convictions. Isolated from everything they produced their collections of topographic maps from their own local survey.After the recall of its exceptional frame, this presentation aims to demonstrate how, through mapping-workshops open to everyone at the Public Library of their village, the children of Battir created their “Treasure Map” from their local proprietary geospatialized data they extend to neighbouring villages.

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