Draft:Geographic coordinates

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Credit: jimht at shaw dot ca.
This map is based on public domain CIA World Fact book image with the Equator bolded in red. Credit: Cburnett.

At present the geographic coordinates on Earth of latitude and longitude translate to right ascension and declination from the Greenwich meridian and the equator as projected on the celestial sphere.

But, other records may exist even here on Earth that use specific stars or bright lights in the sky especially at night that appear fixed relative to others.

Depending on the stability of the rotation of the Earth around its geographic North and South poles, the equator may vary in location.

Coordinates[edit]

Cartesian coordinate system with a circle of radius 2 centered at the origin marked in red. The equation of a circle is (x - a)2 + (y - b)2 = r2 where a and b are the coordinates of the center (a, b) and r is the radius. Credit: 345Kai.

A Cartesian coordinate system specifies each point uniquely in a plane by a pair of numerical coordinates, which are the signed distances from the point to two fixed perpendicular directed lines, measured in the same unit of length. Each reference line is called a coordinate axis or just axis of the system, and the point where they meet is its origin, usually at ordered pair (0,0). The coordinates can also be defined as the positions of the perpendicular projections of the point onto the two axes, expressed as signed distances from the origin.

Fixed point in the sky[edit]

By choosing an equal day/night position among the fixed objects in the night sky, the observer can measure equatorial coordinates: declination (Dec) and right ascension (RA).

The observations require precise measurement and adaptations to the movements of the Earth, especially when and where, for a time, an object or entity is available.

With the creation of a geographical grid, an observer needs to be able to fix a point in the sky. From many observations within a period of stability, an observer notices that patterns of visual objects or entities in the night sky repeat. Further, a choice is available: is the Earth moving or are the star patterns moving? Depending on latitude, the observer may have noticed that the days vary in length and the pattern of variation repeats after some number of days and nights. By choosing an equal day/night position among the fixed objects in the night sky, the observer can measure equatorial coordinates: declination (Dec) and right ascension (RA).

Once these can be determined, the apparent absolute positions of objects or entities are available in a communicable form. The repeat pattern of (day/night)s allows the observer to calculate the RA and Dec at any point during the cycle for a new object, or approximations are made using RA and Dec for recognized objects.

Earth is shown as viewed from the Sun; the orbit direction is counter-clockwise (to the left). Description of the relations between axial tilt (or obliquity), rotation axis, plane of orbit, celestial equator and ecliptic.

Independent of the choice made (Earth moves or not), the pattern of objects is the same for days or nights of the repeating length once a year. The vernal equinox is a day/night of equal length and the same pattern of objects in the night sky. The autumnal equinox is the other equal length day/night with its own pattern of objects in the night sky.

The projection of the Earth's equator and poles of rotation, or if the observer hasn't concluded as yet that it's the Earth that's rotating, the circulating pattern of stars in ever smaller circles heading in specific directions, is the celestial sphere.

Map reliability[edit]

"Ancient maps of seagrass beds are usually available for many areas of the marine realm. For the study area, a series of maps spanning more than one century were available. Biological features of the seagrass Posidonia oceanica made possible an attempt to set up and calibrate a Reliability Index (RI) for these ancient maps. Unfortunately, most of them appear to be totally unreliable. Some other maps are sufficient to provide a rough sketch of the location of the meadows, but not to assess possible changes with time. Finally, a very few recent maps are sufficiently accurate to allow cautious assumptions on meadow dynamics. It is worth noting that (i) whatever the cartographical method, no map of benthic communities is accurate everywhere and at all scales; (ii) the relevance of a map is dependent upon the purpose for which it was established or the utilization that is intended, e.g. short term monitoring of the meadow’s state of health, long term dynamics, coastal development or management of a high value natural heritage community."[1]

Datum shifts[edit]

This map shows the position shift inaccuracies for the Texas Capitol Dome in Austin, Texas, USA. Credit: Peter H. Dana.

"Coordinate values resulting from interpreting latitude, longitude, and height values based on one datum as though they were based in another datum can cause position errors in three dimensions of up to one kilometer."[2]

Equators[edit]

The Intertropical Convergence Zone, or ITCZ, is the region that circles the Earth, near the equator. Credit: GOES Project Science Office.

"The Intertropical Convergence Zone, or ITCZ, is the region that circles the Earth, near the equator, where the trade winds of the Northern and Southern Hemispheres come together. The intense sun and warm water of the equator heats the air in the ITCZ, raising its humidity and making it buoyant. Aided by the convergence of the trade winds, the buoyant air rises. As the air rises it expands and cools, releasing the accumulated moisture in an almost perpetual series of thunderstorms."[3]

"Seasonal shifts in the location of the ITCZ drastically affects rainfall in many equatorial nations, resulting in the wet and dry seasons of the tropics rather than the cold and warm seasons of higher latitudes. Longer term changes in the ITCZ can result in severe droughts or flooding in nearby areas."[3]

"This image [on the right] is a combination of cloud data from NOAA’s newest Geostationary Operational Environmental Satellite (GOES-11) and color land cover classification data. The ITCZ is the band of bright white clouds that cuts across the center of the image."[3]

Ecuador[edit]

This is the equator marker in Cayambe, Ecuador. Credit: Kryptonit.
The volcano Cayambe is located on the equator. Credit: Fabricio Guzmán T.
This shows the equatorial marker Mitad del Mundo, Quito, Ecuador. Credit: Diego Delso.

The volcano Cayambe is located at 0.029°0′0″N 77.986°0′0″W. It is the only permanent snow (glacier) capped peak along the equator.

An equatorial marker in Cayambe, Ecuador, is shown on the right.

Another equatorial marker in Ecuador is Mitad del Mundo, Quito, second image down on the right.

Brazil[edit]

This is the The Marco Zero monument marking the equator in Macapá, Brazil. Credit: Jorge Andrade from Rio de Janeiro, Brazil.

On the right is the equatorial marker in Macapá, Brazil.

São Tomé[edit]

This is an equatorial marker in Sao Tome. Credit: Husond.

The independent nation of São Tomé and Príncipe has an equatorial marker shown on the right in São Tomé.

Gabon[edit]

Le passage de l'Équateur sur la route de Libreville à Lambaréné. Credit: Ballot 2.

On the right is an image of a sign announcing the equator in Gabon in Libreville.

Republic of the Congo[edit]

This map of the Republic of the Congo shows the location of the equator. Credit: United States Central Intelligence Agency's World Factbook.

The equator passes through the Republic of the Congo as shown in the map on the right.

Democraphic Republic of the Congo[edit]

The map shows that the equator passes through the Republic of the Congo. Credit: United States Central Intelligence Agency.

The map on the right shows the equator passing through the Democratic Republic of the Congo.

Uganda[edit]

Equator monument in Uganda is near the city of Masaka. Credit: Iwoelbern.
This map of Uganda shows where the equator passes through. Credit: Travel destinations to visit before you die.

Near the city of Masaka, Uganda, is this equatorial monument in the image on the right.

The map on the left shows approximately where the equator passes through Uganda.

Kenya[edit]

This sign in Kenya is on the equator. Credit: pcb21.
On Africa's east Coast, Kenya straddles the equator and shares a border with Somalia, Ethiopia, Sudan, Uganda and Tanzania. Credit: Geo Systems Global Corporation.

On the right is a sign posted on the equator in Kenya.

The equator passes through Kenya as shown in the map on the left.

Indonesia[edit]

This equator monument is at Pontianak, Indonesia. Credit: Netaholic13.

The equatorial monument at Pontianak, Borneo, Indonesia, has Google Earth Latitude: 0° 8'35.40"N Longitude: 109°15'26.78"L.

Meridians[edit]

The nations of the equator (red) and the prime meridian (blue) are outlined. Credit: NuclearVacuum.

The image on the right shows the nations or territories that touch the Equator (red) or the IERS Reference Meridian (blue), or Prime Meridian.

Infrareds[edit]

Infra-red image from GOES 14 showing the inter Tropical convergence zone. Credit: NASA.

"On August 17, 2009, at 1:31 p.m. EST, the latest NASA/NOAA geostationary weather satellite, called GOES-14, returned its first full-disk thermal infrared (IR) image, showing radiation with a wavelength of 10.7 micrometers emanating from Earth. Infrared images are useful because they provide information about temperatures."[4]

"A band of scattered storms [in the second image down on the right] across the equatorial Pacific shows the location of the Intertropical Convergence Zone, which is a belt of showers and thunderstorms that persists near the equator year round. Need help precisely locating the equator? Look for the dark (hot) spots in the Pacific Ocean west of South America: those are the Galapagos Islands, and the equator passes through the northern tip of the largest island."[4]

Hypotheses[edit]

  1. Each geographic coordinate system throughout hominin experience is correlated to the current latitude and longitude.
  2. If the Earth's rotational axis has varied over hominin experience then current latitude and longitude needs to be corrected to the appropriate past for understanding.

See also[edit]

References[edit]

  1. Agathe Lerichea, Charles-François Boudouresque, Guillaume Bernard, Patrick Bonhomme, and Jacques Denis (February 2004). "A one-century suite of seagrass bed maps: can we trust ancient maps?". Estuarine, Coastal and Shelf Science 59 (2): 353-62. doi:10.1016/j.ecss.2003.09.007. http://www.com.univ-mrs.fr/~Boudouresque/Publications_pdf/Leriche_et_al_2004_Ancient_maps.pdf. Retrieved 2015-10-13. 
  2. Peter H. Dana (21 April 1998). Geodetic Datum Overview. Boulder, Colorado USA: University of Colorado. Retrieved 2015-10-13.
  3. 3.0 3.1 3.2 Charles Ichoku (12 July 2000). The Intertropical Convergence Zone. Washington, DC USA: Earth Observatory, NASA. Retrieved 2015-10-13.
  4. 4.0 4.1 Charles Ichoku (17 August 2009). First IR Image from Newest Weather Satellite Captures Hurricane Bill. Washngton, DC USA: Earth Observatory, NASA. Retrieved 2015-10-13.

External links[edit]

{{Astronomy resources}}{{Mathematics resources}}