Introduction
When you need to accurately enter coordinates in a GIS, the first step is to uniquely define all coordinates on Earth. This means you need a reference frame for your latitude and longitude coordinates. Because the Earth is curved and in GIS we deal with flat map projections we need to accommodate both the curved and flat views of the world. Surveyors have accurately defined locations on Earth. We begin modelling the Earth with an ellipsoid. To be clear, this is different than a geoid which is a measure of mean sea level. Over time, the ellipsoid has been estimated to the best of our ability through a massive collection of surface measurements.
When you combine
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It was in the year 1980 when the need for world geodetic system was recognised by the so called the geodetic community, also within the US Department of Defense.
The earliest used geodetic system no longer provide sufficient data, information, geographic coverage, or product accuracy for all the-current and anticipated applications. The means for producing a new WGS84 were available in the form of improved data, increased data coverage, new data types and improved techniques.
The new world geodetic system called WGS84 is an acronym for World Geodetic System 1984. It is a standard for various activities related to mapping for an example: Navigation, Cartography and Geodesy. The World Geodetic System 1984 (WGS84) is the datum used by the Global Positioning System (GPS).
Within the World Geodetic System (WGS), there are several datums that have been in use throughout the years. These are WGS 60, 70, 72, and 84. The WGS84 is currently one in use for this system. In addition, it is one of the most widely used datums around the
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WGS84 coordinates system are geographically positioned with respect to center of the earth. Such a system is called ECEF (Earth-centered, Earth fixed). The WGS84 coordinate is a three-dimensional, right-handed, Cartesian coordinate point at the center of mass of an ellipsoid, which approximate the total mass of the earth. Figure 2.1 and 2.2 below shows the geographically positioned coordinate with respect to the center (ECEF). And figure 2.3 shows what it is meant by right-handed Cartesian
Dava Sobel’s novel, Longitude: The True Story Of A Lone Genius Who Solved The Greatest Scientific Problem Of His Time is a history of the scientific battle to obtain a method of finding the exact longitude of a specific location. Knowing the longitude of a location may seem unimportant, but in fact it is vital. To fully understand the work that went into this effort, first, one must understand the basic principles for determining location on Earth.
Of course it's important to remember that any direct reckoning position, whether done electronically or manually is only an approximation as it does factor in tidal effects or leeway.
The space-based global navigation satellite system that provides reliable location and time information in all weather and at all times and anywhere on or near the Earth with sub-meter accuracy is called Global Positioning System (GPS) [1]. It consists of a constellation of 28 satellites in six different orbits which give the information of the position of the user with sub meter accuracy [3]. If there are four or more GPS satellites in unobstructed line of sight with the receiver, accurate spatial co-ordinates can be obtained [2]. The datum obtained from the satellites, contain the information about the position and timing by calculating the the Keplerian orbit elements. The location information from GPS is based on the choice of coordinate system and datum [3]. The coordinate systems that are mostly used in GPS are Wor...
The document is in the form of a map which would categorize it as spatial. While it is not a map that could be used to find a specific location, it does follow some of the characteristics of what is expected of a map. It is based on
GPS, or Global Positioning System, helps you to find the place where a geocache is hidden. A geocache is a small box that has a book for a geocacher to sign when he or she finds the box. A geocache can sometimes hold small items that you can keep. If you take the item, you need to put something in its place so the next geocacher can take it. Geocaches are located all over the world and
You need to understand and be able to construct geometric figures by using a compass and a straightedge. Both the compass and the straightedge were used before when the computers were invented. The first person to use a compass and straightedge was Euclid, “the father of geometry”. Drafting with both of these tools were the foundation of all geometric constructions.
The invention of the GPS started with Dr. Ivan Getting leaving his position at Raytheon Company, and armed with the knowledge of what was at the time the most advanced navigational technology in the world, they began developing the Global Positioning System. He, Roger L. Easton, and Bradford Parkison began in the 60’s with a constellation of 24 satellites (placed in six orbital planes) orbiting the earth at a very high altitude (about
Until the 1950s, Atlases were mostly comprised of maps that simply show space and place. However in 1953, the World Geo-Graphic Atlas, published by Walter Paepcke’s Container Corporation of America (CCA) with Herbert Bayer, changed people’s notion of what maps look like and what information they contain. Bayer believed, that maps were “a record of time and perhaps even a tool of prognostication.” By the use of Isotypes (International System of Typographic Picture Education), Bayer created an atlas that is universal, therefore allowed viewers to understand complex data more clearly and easily.
Geographers plan new communities, decide where new highways should be placed, and establish evacuation plans. Computerized mapping and data analysis is known as Geographic Information Systems (GIS), a new frontier in geography. Spatial data is gathered on a variety of subjects and input onto a computer. GIS users can create an infinite number of maps by requesting portions of the data to plot.
Ptolemy was well aware that he knew about only a quarter of the globe, and he knew that his information did not extend to the Eastern Sea. Because Ptolemy derived most of his topographic coordinates by converting measured distances to angles, his maps are distorted. His values for latitude were in error by up to two degrees. For longitude, his measures were even worse, because there was no reliable method to determine geographic longitude; Ptolemy was well aware of this.
Created in 1569, the defining feature of the Mercator map is it's introduction of a projection system that is still in use today. The Mercator projection was created by Gerardus Mercator for use in nautical navigation, and is characterised by its ability to represent straight courses through rhumb lines.19 This map became the standard for most nautical use, and subsequently the most popular type of world map, even until today. The original version of his map notably distorts the sizes of continents, with North America vastly larger than it should be and Europe being displayed as equal in size to Africa. Although more accurate renderings have been made, this distortion is still present in maps today and is an example of Eurocentric bias, whether conscious or
The following is a brief illustration of the principles of GPS. For more information see previous chapter. The Global positioning System (GPS) is a satellite-base navigation system that provides a user with proper equipment access to positioning information. The most commonly used approaches for GPS positioning are the Iterative Least Square (ILS) and the Kalman Filter (EKF) methods. Both of them are based on psuedorange equation:
Longitude are lines, which are also called meridians that run between the North and South Poles. Longitude lines are measured East and West while latitude lines are measured North and South. Both are used to find an exact spot on a map. The prime meridian is 0° longitude, it runs through Greenwich, England. The history of longitude started in around the 1700's when there was a longitude contest being held.
Within Offshore Surveying, GNSS has always been prominent throughout the years. From its initial land based methods of using antenna to the ‘Free-to-Air’ systems used today. Throughout this essay the views in which will be assed are the historical and present day use of GNSS in Offshore Surveying; How GNSS provides the accuracy needed and the limitations it must overcome; What the possible alternatives there could be to GNSS and its advantages and disadvantages faced when using GNSS; The future for GNSS and its development and finally looking at practical real life case studies of GNSS and how it is effectively used within an offshore surveying company. The essay will look at these points individually and separate itself accordingly into five many sections reflecting the points rose previously to give an accurate account of the role GNSS has had, and will play, in Offshore Surveying.
The Global Positioning System consists of three sections, 1.satellites which are orbiting the planet, 2.there are numerous control/monitoring centers here on the ground, and 3. gps receivers which are used by their owners. The satellites send down signals from orbit, which are received by GPS receivers on the ground in the air or on the water, the GPS receiver then converts this information into a location longitude, latitude and altitude along with time.