mercator definition geography


A natural extension of the plate tectonic methodology is its use for quantitative reconstruction of continents and ocean basins in the geologic past. The whole globe is sliced in 60, 6 fuses, with the Greenwich meridian lying between fuses 30and 31. Maps are prepared by specialists who view the photographs through a stereoscope. Thousands of points across the United States have had their latitudes and longitudes determined accurately and marked with ground monuments by the National Geodetic Survey (formerly the Coast and Geodetic Survey). The advantage is that no point is too far away from the central meridian, so the distortions in the fuse are small, but this benefit is achieved at the expense of the discontinuities. It is the de facto standard for web maps and online services. and The standard Mercator projection has the cylinder oriented North-South (Fig. The TM apparatus in particular is used for coastal monitoring through its thermal infrared bands. For example, extensive efforts to create a global mangrove map have been made using satellite-based remote sensing (Spalding et al., 1997). This is based on the transverse Mercator projection and covers the earth's surface between 80 south and 84 north latitudes. The eastings of the origin of each zone is 500,000m. Regarding northings, for the northern hemisphere it is 0 at the equator and for southern hemisphere, it is 1,000,000m at the equator. By continuing you agree to the use of cookies. Later, in 1977, a cylindric projection was developed by Snyder that displayed the ground tracks of the Landsat satellite as straight lines (see Figure 14). The bottom-most zone (80S to 72S) is assigned letter C and the topmost letter X. An Album of Map This map projection is practical for nautical applications due to its ability to represent lines of constant course, known as rhumb lines, as straight segments that conserve the angles with the meridians. Distances are true along the equator or along the secant latitudes (standard parallels). (ellipsoids), the projected coordinate system must be based on a

administrative boundaries (national, regional, and local), infrastructures (road, rails, and structures), and. Many developments occurred as a result of the space program, which required, on the one hand, very accurate determination of relative locations of space tracking stations around the world and, on the other hand, detailed mapping of the moon as well as planets and other stars. The poles project to infinity and cannot be shown on the map. The model utilizes the bathymetry data in the original. Throughout it all, however, surveyors must be knowledgeable in the basic fundamentals of surveying and must constantly exercise good professional judgment in interpreting and utilizing results from the sophisticated instrumentation available. Each UTM zone is assigned a number. Geological Survey Professional Paper 1395. Washington, DC: United The Web Mercator variant of the projection is the de facto standard for web maps and online services. Figure 3 shows an example of NOS estuarine bathymetry (combining bathymetry and land topography) for San Francisco Bay. Where subduction plays major role, namely, the Pacific Ocean, it is not possible to estimate the past position of continents from magnetic lineations alone, but the evolution of the Pacific Ocean itself and its margin can be discussed (Hilde et al., 1977). One example is the Albers projection shown here in Fig. Developing a projection that displayed the ground track of the satellites swath path at correct scale that was also conformal proved to be a problem. It is available in, Mercator variant C differs from variant B only in projection parameters. (Eds. It is derived from several raster and vector sources of topographic information. The model utilizes the bathymetry data in the original Mercator projection format of the Smith and Sandwell data, where the grid cells become smaller for locations farther away from the equator. In the 1990s, topographic map creation entered the digital era. In practice, a number of photographs are made as the airplane flies a prescribed course so that they will overlap one another. Cartographica, The International Journal for Geographic Information and Geovisualization, Mercator is also known as Mercator variant B. Maps came into general use in the fifteenth and sixteenth centuries in Europe (e.g., the development of the. Corrections? On the other hand, even if it conforms, the size of the shapes and the direction of lines can change when they are moved. The meridians are equally spaced parallel vertical lines, and the parallels of latitude are parallel horizontal straight lines that are spaced farther and farther apart as their distance from the Equator increases. McKenzie and Parker (1967) investigated the relative motion of the Pacific Plate and the North American Plate, and saw that the projections onto the horizontal plane of slip vectors of several earthquakes at the boundaries of these two plates were nearly parallel to the lines of latitude in a Mercator projection with Euler pole at 50N, 85W. This is the process of creating a map of the Earth's surface all of which distort the Earth's surface in some way as originally proved by Gauss who said that no sphere can be represented on a plane without distortion. In the Northern Hemisphere, this origin is on the equator; in the Southern Hemisphere it is 10,000,000 m south of the equator. However, the eventual watershed projection for navigation was the Mercator projection (see Figure 12b), developed by Gerardus Mercator in 1569, and probably one of the most recognizable projections. Where dated sea-floor spreading magnetic lineation patterns are available on both sides of a ridge, the part of the sea floor between the ridge and an isochron can be resorbed by appropriately rotating the plates and this gives past positions of the plates (continents and ocean basins). The coordinate system for each state was established by projecting, mathematically, its surface onto the surface of a cone or cylinder (or, in some cases, both), which surface can then be developed into a plane. The International Society for Mangrove Ecosystems, Okinawa, Japan, 178 pp. The precise location of any point on the earth's surface can be specified by giving its latitude, longitude, and elevation above mean sea level. Our editors will review what youve submitted and determine whether to revise the article. This expanding frontier greatly increased geographic knowledge and the need for maps to represent these new discoveries. In 2000, the Shuttle Radar Topography Mission (SRTM) completed collection of elevation data on a near-global scale to generate the most completed high-resolution digital topographic database of the Earth possible at the time. Figure7.26. In the 1990s, more varieties of apparatus were developed. Battersby, S., Finn, M. P., Usery, E. L. and Yamamoto, K. (2014). It is available in, Mercator variant A differs from variant B only in projection parameters. Ye Yincan et al, in Marine Geo-Hazards in China, 2017. The MOST model that is used to generate the scenarios and the bathymetry for the Pacific Ocean is based on the Smith and Sandwell (1994) 2 arc minute data set. The data are subsampled to twice coarser resolution(4 arc minutes at the equator) of the original data set. A false origin is established 500,000 m west of the central meridian of each UTM zone. This projection is a conic, equal area map projection that uses two standard parallels. This characteristic was particularly useful to navigators in that they could lay out a rhumb line on the map and then follow its compass direction from the origin to destination. The UTM system involves establishing 60 north-south zones, each of which is six degrees longitude wide. Distortion values are the same along a particular parallel and they are symmetric across the equator and the central meridian. A more intuitive picture would be a world map using a Mercator projection, but with the Euler pole APB as its pole. over a period of time. For example, New York uses a Lambert projection for Long Island and three Mercator projections for the rest of the state. By signing in, you agree to our Terms and Conditions 12.3. Worldwide bathymetry can be obtained from the General Bathymetric Chart of the Oceans (GEBCO). To describe the motion of, say, the North American Plate, one does not have to specify how many kilometers San Francisco moved in which direction, or what happened to New York, etc. There are four variants available in ArcGIS: The poles cannot be represented on the Mercator projection. the web services. There are, of course, many other mathematical formulations for map projections that do not fit easily into any of these classification schemes. It should be clear that substantial savings in time are realized in gathering data by means of photogrammetry compared to more conventional means; and although the costs of operating an aircraft may be high, they are more than offset by savings in time and salaries paid. Copyright 2022 Elsevier B.V. or its licensors or contributors. If the time of observation and location (latitude and longitude) of the observation point are known, the exact position of the celestial body can be determined from an almanac of celestial body positions (known as an ephemeris).

Examples are cylindrical (e.g., Mercator), conical (e.g., Albers), and azimuthal or planar (e.g., stereographic used frequently for polar maps). The most primitive type of geospatial data is maps. Mass produced paper engravings shaped like 12 gores were glued to hollow globes with 2 additional circular polar end caps. Any straight line drawn on this projection represents an actual compass bearing. The purpose of a map projection is to specify the transformation between the curved elliptical surface of the Earth and the flat planar surface of the map. In addition, each zone overlaps by two degrees into adjoining zones. Figure7.25. The portolan chart was one of the first navigational aids that enabled sailors to lay out a sailing course on a map. The TMU was set to 0.50.1 acre, and topographic data were able to be stored as a global digital elevation model (DEM) instead of a visual image. At the time, cartographers saw GIS as a new and wildly popular tool that appeared insensitive to these ethical arguments. Other relevant specific details of the model configuration are: spatial resolution: 4 arc minutes, minimum offshore depth: 20m, time step: 15s, sea level (and depth-averaged currents) at every fourth grid point are saved every four time steps (i.e., 1min) and the model is run for 24h of model time. The meridians are vertical lines, parallel to each other, and equally spaced, and they extend to infinity when approaching the poles. If the Mercator implementation supports spheroids Also, in areas covered by sand (deserts or beaches) or snow, lack of change in color and texture of the ground makes interpretation of the ground surface difficult. A more intuitive picture would be a world map using a, Environmental Monitoring and Characterization, is also shown on most topographic maps published by the USGS. The Universal Transverse Mercator (UTM) projection, developed by the U.S. Army, is widely used in topographic maps. Equidistant projections are used for radio and seismic mapping and often for ship navigation. For the model forecasts considered here, the NOAA system uses inversion techniques to select the best combination of unit source functions in order to match observations of sea level from the tsunami meters (Gica etal., 2008; Titov etal., 2005). U.S. Geological Survey Professional Paper 1453. A particular transverse Mercator projection called the Universal Transverse Mercator (UTM) is probably the most recommended one from latitudes 84N to 80S (Fig. It is available in, Mercator auxiliary sphere does not support the ellipsoid and uses sphere-based equations with a sphere specified by the Auxiliary Sphere Type parameter. The ability to compute measures such as area to large numbers of decimal places served to reinforce this view, and it was clear that GIS was being marketed by commercial software developers as a scientifically rigorous approach to geographic problems. Snyder, J. P. and Voxland, P. M. (1989). It is also used for marine navigation since the lines of constant direction appear as straight lines on the map. The rake is set at 90, as in T1. It may be normal so that the map surface of symmetry coincides with the Earth's axis or it may be transverse that is at right angles to the Earth's axis. A circle centered on Pyongyang and superimposed on a Mercator projection. Furthermore, the oceanic environment, including marine winds, radiative processes, airsea interaction, wind waves and wind, ice, ocean currents, and landocean interactions, have been monitored using satellite images (Jones et al., 1993). M.F. Another problem is encountered in an area of extraordinarily dense growth (e.g., a rain forest), which, of course, makes it difficult or impossible to see the ground surface. This projection is recommended for areas lying between 84N to 80S. It operates under the joint auspices of the Intergovernmental Oceanographic Commission (IOC) (of the United Nations Educational, Scientific and Cultural Organization (UNESCO)) and the International Hydrographic Organization (IHO). 8). The graticule is symmetric across the equator and the central meridian. Kessler, in International Encyclopedia of Human Geography, 2009. Yes! The Mercator projection was developed by Gerardus Mercator in 1569. All rights reserved. Using Euler's Fixed Point Theorem, one can conveniently express the displacement of a plate by a rotation around its Euler pole (see Chapter 7 by Stein and Klosko). Latitude zones are 8 high and are labeled from C to X, omitting the letters I and O, beginning at 80S. The US Geological Survey (USGS) established protocols for using 1:130K aerial photographs to obtain 510-acre resolution, that is, the target mapping unit (TMU). Back when sailing ships was common, since longitudes could not be determined accurately, the distance being travelled was not important and the same went for the direction taken. Many recent developments in surveying, some of which have been mentioned, provide measurement with greater accuracy than could have even been anticipated a few years ago. Both are coordinate systems that use a metric-based Cartesian grid laid out on a conformally projected surface. The fact that the camera sees everything ensures that a vast amount of data will be obtained and virtually no detail will be overlooked in the field. While great efforts have been made by developers of the more elaborate GIS packages to include support for sophisticated cartographic techniques, such as methods of cartographic generalization and alternative techniques for assigning class intervals to choropleth maps, nevertheless it is easy to find examples of the misuse of GIS. Figure7.24. Today, satellite ground-tracking maps rely upon the equirectangular projection, with curved rather than straight orbital paths being shown. We see that the direction of the relative motion (i.e., the transform fault) is parallel to the lines of latitude, and the length of the vector that represents the relative velocity is constant regardless of latitude. Confirmation of these predictions was the starting point of plate tectonics. This is based on the transverse, Google Earth abandons many of the cherished icons of cartography such as projections, rendering them largely irrelevant, and in this sense can be seen as threatening to a discipline's cherished expertise. Ptolemys principle affected the said rhumb lines to be curvy and navigators needed to recalculate their bearing as they steer in order to account the changes. For example, he determined the Euler pole of the relative motion between the American and African Plates (1) from the points of intersection of great circles perpendicular to both transform faults and slip vectors of earthquakes associated with the Mid-Atlantic Ridge and (2) by matching the distribution of spreading rates with the relations of sin(q). Mercator is a conformal map projection. In 1972, the first Earth observation satellite, Landsat, was launched by the US.

Typical spectral responses of important ground attributes. Conformal maps are used for navigational or meteorological charts.

Sign up to make the most of YourDictionary. Straight line segments represent true bearings, thus making this projection useful for navigation. Letters A, B, Y, and Z are used in the polar regions by the Universal Polar Stereographic (UPS) grid system. The sphere's radius is equal to the WGS 1984 semimajor axis, 6378137.0 meters. However, geometric shapes on the map can be moved around without distorting the whole illustration. Reproduced with permission from GEBCO world map. Figure 2. Figure 1. The true azimuth of a line can be determined by astronomical observation by setting up a transit over one end of the line, sighting on a particular celestial body, and reading the vertical and horizontal angles to the line in question. Back in the day, labor-intensive processes were followed in mass-producing globes. Consider the case of two plates A and B (Fig. SRTM consisted of a specially modified radar system that flew onboard the space shuttle Endeavour during an 11-day mission in February of 2000. Seiya Uyeda, in International Geophysics, 2002. HENDRICKS, in Environmental Monitoring and Characterization, 2004. Jain, V.P. However, the eventual watershed projection for navigation was the, Orbital Mechanics, Image Navigation, and Cartographic Projections, International Handbook of Earthquake and Engineering Seismology, Part A, B. Privacy Policy. When plate tectonics was introduced, its goal was to substantiate the supposed rigid motion of plates. Let us know if you have suggestions to improve this article (requires login). Significant improvements in cameras, film, plotting instruments, and other devices have made it possible to produce maps that meet high accuracy standards. Figure 14. This made it possible for the entire globe to be drawn on a flat sheet. Mercator is a cylindrical projection. Scale is constant along any line of parallel (latitude) in the direction of the latitude. DOI: 10.3138/carto.49.2.2313. A conformal cylindric projection, the Mercator, was never intended to be displayed as a world map, although many atlases of the nineteenth and twentieth centuries relied heavily upon this projection for their world maps. He took into consideration not only slip vectors of earthquakes and the directions of transform faults, but also the distribution of the spreading rate estimated from the width of geomagnetic stripes. SRTM is an international project spearheaded by the National Geospatial-Intelligence Agency (NGA) and the National Aeronautics and Space Administration (NASA). Distortions of this projection occur in the northsouth direction; hence, it is used for states with relatively short northsouth dimensions (such as Tennessee and North Carolina). An additional feature of this projection is that all local shapes are accurate and correctly defined at infinitesimal scale. For example, several recent news stories of the missile threat of North Korea have included maps purporting to show the areas reachable by missiles of a given range launched from Pyongyang by drawing concentric circles on a, Encyclopedia of Physical Science and Technology (Third Edition), 2 arc minute data set. Figure 12.3. The lines of latitude are horizontal straight lines, perpendicular to the meridians and the same length as the equator, but they become farther apart toward the poles. The National Oceanic and Atmospheric Administration (NOAA) provided regional sets of digital bathymetry data in the United States as the National Ocean Service (NOS)s Estuarine Bathymetry. The portolan chart was one of the first navigational aids that enabled sailors to lay out a sailing course on a map. Gores are shapes that narrow when approaching the poles. Therefore, the Web Mercator coordinate system is not conformal, and besides enormous area and distance distortions away from the equator, it also does not project rhumb lines as straight lines. The satellite is used for land-based resource mining and environmental monitoring. Similarly, GIS enables anyone equipped with data and a few simple tools to produce a map that previously would have required the expertise of a trained cartographer. sphere-based geographic coordinate system. "Implications of Web Mercator and Its Use in Online Mapping." GEBCO produces a range of bathymetric data sets and products, including global gridded bathymetric data sets: the GEBCO_08 Grid (at 30-arcsec intervals) and GEBCO One Minute Grid (at 1-arcmin intervals); a global set of digital bathymetric contours; the GEBCO Gazetteer of Undersea Feature Names; the GEBCO Digital Atlas, and the GEBCO world map (Figure 2). GEBCO aims to provide the most authoritative, publicly available bathymetry of the worlds oceans. Another dimension to this argument surfaced in the early 1990s as part of a rapidly emerging social critique of GIS. water districts (seas, lakes, and rivers). Jack B. Evett, in Encyclopedia of Physical Science and Technology (Third Edition), 2003. With this coordinate system, the geodetic coordinates defined on the WGS 84 datum are projected as if they were defined on a sphere, using a sphere-based version of the Mercator projection. UTM coordinates are shown on the edges of many USGS topographic maps. The origin of each zone is located at a point at the equator where it is intersected by the central meridian of the zone. Map Projections: A Working Manual. U.S. Geological Survey Professional Paper 1453. It contributed to boosting remote-sensing technologies. The distortion given by the Mercator projection near the equator is very minimal. Each unit source function is equivalent to a tsunami generated by a Mw 7.5 earthquake with a rectangular fault 100km by 50km in size and 1m slip. The US Geological Survey uses a conformal projection for many of its topographic maps. I want to receive exclusive email updates from YourDictionary. Only a few types will be presented here as examples, but the interested reader can find many volumes that are addressed to subject of map projections (e.g. Map Projections: A Working Manual. This had an effect on sailors rhumb lines. While great efforts have been made by developers of the more elaborate GIS packages to include support for sophisticated cartographic techniques, such as methods of cartographic generalization and alternative techniques for assigning class intervals to choropleth maps, nevertheless it is easy to find examples of the misuse of GIS. Maps are often persuasive, capable of influencing opinion and policy; and just as the playing of concert pianos is limited to a few experts, so also the creation of maps should be limited to trained professionals. In simple terms, photogrammetry consists of photographing the property in question from an airplane, viewing the aerial photographs, and preparing a topographic map therefrom. Two methods exist for emulating the Mercator projection used by It used 1:56K colored aerial photographs to obtain 13-acre TMU, which was then followed by using 1:40K aerial photographs with 1-acre TMU. The subsections below describe the Mercator projection properties.

This allows easy reference to points that are near a zone boundary, regardless of which zone is in use for a particular project. Le Pichon (1968) pioneered this type of reconstruction, which has been followed by many, including McKenzie and Sclater (1971) for the Indian Ocean and Pitman and Talwani (1972) for the Atlantic Ocean. Although latitude and longitude and the Public Land Survey are the most often used system for determining locations on the earth, a third method, which is somewhat more complicated, called the Universal Tranverse Mercator (UTM) Grid System, is also shown on most topographic maps published by the USGS. Generally, maps include the following information: natural landmarks (mountains, valleys, and plains). Bathymetry data sets are offered in the DEM format in both 30-m and 3-arcsec resolutions for 70 estuaries. Standard Mercator projection. Map projections can be classified by the type of projection surface onto which the globe is projected. He then drew a Mercator projection with the Euler pole thus obtained as its pole, and demonstrated that the two shoulds stated above were satisfied. As in other such projections, the areas farther from the equator appear larger, making the polar regions greatly distorted. Microcomputers can automatically record data, make appropriate computations, and prepare maps. GIS seemed to be grounded in the nave assumption that one could achieve a scientifically rigorous description of the world, and store it in precise form in a digital computer that the contents of a GIS database represented the results of objective, replicable scientific measurement. Let us write the rotation of Plate A relative to Plate B as ARB, its Euler pole as APB, and relative velocity and relative angular velocity as AVB, and AB. The inversion defines the scaling coefficients for each unit source in the combination. Unfortunately, the result is a severe underestimate of the areas that can be reached (Figure 1). All meridians can be projected, but the upper and lower limits of latitude are at 89 north and 89 south. It is a digital raster compilation of NOS hydrographic survey data for selected US estuaries. These distortions can be minimized depending on the specific application of the map projection. 7.26A). ), 1997.

Although the linear scale is equal in all directions around any point, thus preserving the angles and the shapes of small objects, the Mercator projection distorts the size of objects as the latitude increases from the equator to the poles, where the scale becomes infinite. As in other cases, adequate horizontal and vertical control systems must be employed to ensure sufficient accuracy. These are similar to the T1 Mw 7.5 events (see Table5.1). Various modern devices utilizing lasers, infrared light, and so on provide extremely accurate determinations of elevations, distances, and directions.

He divided the Earth's surface into six large plates, and tried to find, by the method of least squares, the set of plate motions that would best fit with both the width of geomagnetic stripes and the strikes of the transform faults. From this information, the true azimuth of the line to the celestial body and then the true azimuth of the line in question can be calculated. Although they are widely used and provide adequate results, they have at least two limitations, particularly when applied to surveys over large areas. Mercator discovered that in order for the rhumb lines to remain straight, the latitude lines should be away from each other as these lines approach north and south of the Earths equator. While the covered elevations do not extend beyond the high water line, these data provide important information on estuarine resources.
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