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১ নং লাইন:
{{কাজ চলছে/২০১৯}}
'''ভূগাণিতিক উপাত্ত''' বা '''ভূগাণিতিক সিস্টেম''' (এছাড়াও: '''ভূগাণিতিক প্রসঙ্গ উপাত্ত''' বা '''ভূগাণিতিক প্রসঙ্গ সিস্টেম''') হচ্ছে একটি [[স্থানাঙ্ক ব্যবস্থা]] এবং প্রসঙ্গ বিন্দুর একটি সেট যা [[পৃথিবী|পৃথিবীর]] বিভিন্ন স্থানের (অথবা অনুরূপ বস্তুর) অবস্থান সনাক্ত করতে ব্যবহৃত হয়। [[সমুদ্র সমতল|সমুদ্র সমতলের]] আনুমানিক ডেটাম এর মান [[
[[মানচিত্র]] (কাগজ বা ডিজিটাল) এর উপর অবস্থানের অবস্থানগুলি [[পৃথিবী|পৃথিবীর]] তাদের প্রকৃত অবস্থানগুলিতে নির্দেশিত অবস্থানগুলি অনুবাদ করতে [[মানচিত্রাঙ্কনবিদ্যা|কার্টোগ্রাফার]] এবং [[কৃত্রিম উপগ্রহভিত্তিক দিকনির্ণয়|উপগ্রহের নেভিগেশান সিস্টেমগুলি]] দ্বারা জিওডসি, [[দিক নির্ণয়|নেভিগেট]], এবং [[ভূমি জরিপ|সার্ভে]] ব্যবহার করা হয়। প্রতিটি একটি ellipsoid (প্রসারিত গোলক) সঙ্গে শুরু হয়, এবং তারপর [[অক্ষাংশ]], [[দ্রাঘিমাংশ]] এবং উচ্চতা সমন্বয় সংজ্ঞায়িত। পৃথিবীর পৃষ্ঠের এক বা একাধিক অবস্থান নোঙ্গর হিসাবে "বেস পয়েন্ট" হিসাবে নির্বাচিত হয়।
The difference in co-ordinates between datums is commonly referred to as ''datum shift''. The datum shift between two particular datums can vary from one place to another within one country or region, and can be anything from zero to hundreds of meters (or several kilometers for some remote islands). The [[North Pole]], [[South Pole]] and [[Equator]] will be in different positions on different datums, so [[True North]] will be slightly different. Different datums use different interpolations for the precise shape and size of the Earth ([[reference ellipsoid]]s).
Because the Earth is an imperfect ellipsoid, localised datums can give a more accurate representation of the area of coverage than WGS 84. [[Ordnance Survey National Grid|OSGB36]], for example, is a better approximation to the [[geoid]] covering the British Isles than the global WGS 84 ellipsoid.<ref>{{
Horizontal datums are used for describing a point on the [[Earth]]'s surface, in [[latitude]] and [[longitude]] or another coordinate system. Vertical datums measure elevations or depths.
১৬ ⟶ ১৫ নং লাইন:
=== অনুভূমিক উপাত্ত ===
The horizontal datum is the model used to measure positions on the Earth. A specific point on the Earth can have substantially different coordinates, depending on the datum used to make the measurement. There are hundreds of local horizontal datums around the world, usually referenced to some convenient local reference point. Contemporary datums, based on increasingly accurate measurements of the shape of the Earth, are intended to cover larger areas. The [[WGS 84]] datum, which is almost identical to the [[NAD83]] datum used in North America and the [[ETRS89]] datum used in Europe, is a common standard datum.{{citation needed|date=November 2016}}For example, in Sydney there is a 200 metres (700 feet) difference between GPS coordinates configured in GDA (based on global standard WGS 84) and AGD (used for most local maps), which is an unacceptably large error for some applications, such as [[surveying]] or site location for [[scuba diving]].<ref>McFadyen, [http://www.michaelmcfadyenscuba.info/viewpage.php?page_id=80 GPS and Diving] {{
=== উল্লম্ব উপাত্ত ===
{{
== ভূগাণিতিক স্থানাঙ্ক ==
{{
[[চিত্র:Geocentric_vs_geodetic_latitude.svg|ডান|থাম্ব|300x300পিক্সেল|The same position on a [[spheroid]] has a different angle for latitude depending on whether the angle is measured from the normal line segment ''CP'' of the [[ellipsoid]] (angle ''α'') or the line segment ''AP'' from the center (angle ''β''). Note that the "[[wikt:flatness|flatness"]] of the spheroid (orange) in the image is greater than that of the Earth; as a result, the corresponding difference between the "geodetic" and "geocentric" latitudes is also exaggerated.]]
In geodetic coordinates, the Earth's surface is approximated by an [[Earth ellipsoid|ellipsoid]], and locations near the surface are described in terms of [[latitude]] (<math>\phi</math>), [[longitude]] (<math>\lambda</math>), and height (<math>h</math>).<ref group="note">About the right/left-handed order of the coordinates, i.e., <math>(\lambda, \phi)</math> or <math>(\phi, \lambda)</math>, see [[Spherical coordinate system#Conventions]].</ref>
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=== রাশি প্রতিপাদন ও সংজ্ঞায়িতকরণ ===
{{
{| class="wikitable"
!Parameter
৬২ ⟶ ৬১ নং লাইন:
== আলোচনা এবং উদাহরণ ==
{{
The [[North American Datum]] of 1927 (NAD 27) is "the horizontal control datum for the United States that was defined by a location and azimuth on the Clarke spheroid of 1866, with origin at (the survey station) [[Meades Ranch Triangulation Station|Meades Ranch (Kansas)]]." ... The geoidal height at Meades Ranch was assumed to be zero, as sufficient gravity data was not available, and this was needed to relate surface measurements to the datum. "Geodetic positions on the North American Datum of 1927 were derived from the (coordinates of and an azimuth at Meades Ranch) through a readjustment of the triangulation of the entire network in which Laplace azimuths were introduced, and the Bowie method was used." (http://www.ngs.noaa.gov/faq.shtml#WhatDatum ) NAD27 is a local referencing system covering North America.
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The North American Datum of 1983 (NAD 83) is "The horizontal control datum for the United States, Canada, Mexico, and Central America, based on a geocentric origin and the Geodetic Reference System 1980 ([[GRS80]]). "This datum, designated as NAD 83 ...is based on the adjustment of 250,000 points including 600 satellite Doppler stations which constrain the system to a geocentric origin." NAD83 may be considered a local referencing system.
WGS 84 is the [[World Geodetic System]] of 1984. It is the reference frame used by the [[United States Department of Defense|U.S. Department of Defense]] (DoD) and is defined by the [[National Geospatial-Intelligence Agency]] (NGA) (formerly the Defense Mapping Agency, then the National Imagery and Mapping Agency). WGS 84 is used by DoD for all its mapping, charting, surveying, and navigation needs, including its [[GPS]] "broadcast" and "precise" orbits. WGS 84 was defined in January 1987 using Doppler satellite surveying techniques. It was used as the reference frame for broadcast GPS Ephemerides (orbits) beginning January 23, 1987. At 0000 GMT January 2, 1994, WGS 84 was upgraded in accuracy using GPS measurements. The formal name then became WGS 84 (G730), since the upgrade date coincided with the start of GPS Week 730. It became the reference frame for broadcast orbits on June 28, 1994. At 0000 GMT September 30, 1996 (the start of GPS Week 873), WGS 84 was redefined again and was more closely aligned with [[International Earth Rotation Service]] (IERS) frame [[International Terrestrial Reference System|ITRF]] 94. It was then formally called WGS 84 (G873). WGS 84 (G873) was adopted as the reference frame for broadcast orbits on January 29, 1997.<ref>{{
The WGS 84 datum, within two meters of the NAD83 datum used in North America, is the only world referencing system in place today. WGS 84 is the default standard datum for coordinates stored in recreational and commercial GPS units.
৮৩ ⟶ ৮২ নং লাইন:
* [[European Terrestrial Reference System 1989|ETRS89]], the European Datum, related to [[International Terrestrial Reference System and Frame|ITRS]]
* [[ED50]], the older European Datum
* [[GDA94]], the Australian Datum<ref>{{
* [[JGD2011]], the Japanese Datum, adjusted for changes caused by [[2011 Tōhoku earthquake and tsunami]]<ref>{{
* [[Tokyo97]], the older Japanese Datum<ref>{{
* [[KGD2002]], the Korean Datum<ref>{{
* [[TWD67]] and [[TWD97]], different datum currently used in Taiwan.<ref>{{
* [[BJS54]] and [[XAS80]], old geodetic datum used in China<ref>[http://www.chinaminingmagazine.com/ch/reader/view_abstract.aspx?file_no=20141431&flag=1 Analysis of Conversion Method and Map Merging from BJS54 XA80 Surveying and Mapping Results to CGCS2000] {{
* [[Restrictions on geographic data in China#GCJ-02|GCJ-02]] and [[Baidu Maps#Coordinate system|BD-09]], Chinese encrypted geodetic datum.
* [[PZ-90|PZ-90.11]], the current geodetic reference used by [[GLONASS]]<ref>{{
* [[GTRF]], the geodetic reference used by [[Galileo (satellite navigation)|Galileo]]<ref name="GNSS2">{{
* [[CGCS2000]], or [[CGS-2000]], the geodetic reference used by [[BeiDou Navigation Satellite System]]<ref name="GNSS2" /><ref>Handbook of Satellite Orbits: From Kepler to GPS, Table 14.2</ref><ref>[http://www.beidou.gov.cn/attach/2013/12/26/20131226b8a6182fa73a4ab3a5f107f762283712.pdf BeiDou Navigation Satellite System Signal In Space Interface Control Document, Open Service Signal (Version 2.0)] {{
* [[International Terrestrial Reference Frame]]s (ITRF88, 89, 90, 91, 92, 93, 94, 96, 97, 2000, 2005, 2008, 2014), different realizations of the [[International Terrestrial Reference System|ITRS]].<ref>{{
* [[Hong Kong Principal Datum]], a vertical datum used in Hong Kong.<ref>{{
== আরও দেখুন ==
১১০ ⟶ ১০৭ নং লাইন:
* [[Ordnance Datum]]
* [[World Geodetic System]]
== পাদটীকা ==
{{
== তথ্যসূত্র ==
{{সূত্র তালিকা|2}}
<!--See [[Wikipedia:Footnotes]] for an explanation of how to generate footnotes using the <ref(erences/)> tags-->
১৩৬ ⟶ ১৩১ নং লাইন:
* [http://www.ngs.noaa.gov/faq.shtml#WhatDatum NGS FAQ – What is a geodetic datum?]
* [http://kartoweb.itc.nl/geometrics/Reference%20surfaces/body.htm About the surface of the Earth] on [http://kartoweb.itc.nl kartoweb.itc.nl]
{{DEFAULTSORT:Geodetic System}}
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