View source for Geographical exploration

{{Short description|Act of searching for unknown space}}

[[File:Theatrum Orbis Terrarum, by Abraham Ortelius, World, 1572.jpg|thumb|upright=1.35|[[Abraham Ortelius]]'s 1570 world map, the world's first modern atlas.]]
'''Geographical exploration''', sometimes considered the default meaning for the more general term '''exploration''', refers to the practice of discovering remote lands and regions of the planet [[Earth]].<ref name=":0">{{Cite book |author=[[Royal Geographical Society]] |url=https://books.google.com/books?id=uo8SAQAAIAAJ |title=Atlas of Exploration |date=2008 |publisher=[[Oxford University Press]] |isbn=978-0-19-534318-2 |language=en |access-date=October 6, 2022 |archive-date=October 16, 2022 |archive-url=https://web.archive.org/web/20221016144552/https://books.google.com/books?id=uo8SAQAAIAAJ |url-status=live |via=[[Google Books]]}}{{page needed|date=January 2023}}</ref> It is studied by geographers and historians.{{citation needed|date=January 2023}}

Two major eras of exploration occurred in human history: one of convergence, and one of divergence.{{clarify|What do convergence and divergence mean in this context? are they in the right order?|date=January 2023}} The first, covering most of ''[[Human|Homo sapiens]]'' history, saw humans [[Recent African origin of modern humans|moving out of Africa]], settling in new lands, and developing distinct cultures in relative isolation.<ref name=":1" /> Early explorers settled in Europe and Asia; 14,000 years ago, some crossed the [[Settlement of the Americas|Ice Age land bridge]] from Siberia to Alaska, and moved southbound to settle in the Americas.<ref name=":0" /> For the most part, these cultures were ignorant of each other's existence.<ref name=":1" /> The second period of exploration, occurring over the last 10,000 years, saw increased cross-cultural exchange through trade and exploration, and marked a new era of cultural intermingling, and more recently, convergence.<ref name=":1">{{Cite book |last=Fernández-Armesto |first=Felipe |url=https://books.google.com/books?id=6bYQAAAAQBAJ |title=Pathfinders: A Global History of Exploration |date=October 17, 2007 |publisher=[[W. W. Norton & Company]] |isbn=978-0-393-24247-8 |language=en |via=[[Google Books]] |access-date=October 6, 2022 |archive-date=October 16, 2022 |archive-url=https://web.archive.org/web/20221016144552/https://books.google.com/books?id=6bYQAAAAQBAJ |url-status=live}}</ref>

Early writings about exploration date back to the 4th millennium B.C. in [[ancient Egypt]]. One of the earliest and most impactful thinkers of exploration was [[Ptolemy]] in the 2nd century AD.{{clarify|Impactful in what way?|date=January 2023}} Between the 5th century and 15th century AD, most exploration was done by Chinese and Arab explorers. This was followed by the [[Age of Discovery]] after European scholars rediscovered the works of early Latin and Greek geographers. While the Age of Discovery was partly driven by European land routes becoming unsafe,<ref>{{Cite web |title=European exploration – The Age of Discovery {{!}} Britannica |url=https://www.britannica.com/topic/European-exploration/The-Age-of-Discovery |access-date=2022-10-06 |website=britannica.com |language=en}}</ref> and a desire for conquest, the 17th century saw exploration driven by nobler motives, including scientific discovery and the expansion of knowledge about the world.<ref name=":0" /><!-- citation applies to the entire paragraph (see the Royal Geographic Society Atlas's Foreword page) --> This broader knowledge of the world's geography meant that people were able to make [[world map]]s, depicting all land known. The first modern [[atlas]] was the ''[[Theatrum Orbis Terrarum]]'', published by [[Abraham Ortelius]], which included a world map that depicted all of Earth's continents.<ref name="GLO Chapter 2">{{cite report |title=Global Land Outlook |date=2017 |publisher=[[United Nations Convention to Combat Desertification]] |isbn=978-92-95110-48-9 |access-date=November 3, 2022 |chapter-url=https://www.unccd.int/sites/default/files/2018-06/GLO%20English_Ch2.pdf |chapter=Chapter 2 – Brief History of Land Use—}}</ref>{{rp|page=32}}

==Concept==
{{Main|Exploration}}

Exploration is the process of exploring, which has been defined as:<ref>{{cite web|author=((Wiktionary contributors)) |title=explore |publisher=Wiktionary, The Free Dictionary |date=30 November 2022 |url=https://en.wiktionary.org/w/index.php?title=explore&oldid=70015629 |access-date=29 December 2022 }}</ref>
* To examine or investigate something systematically.
* To travel somewhere in search of discovery.
* To examine diagnostically.
* To (seek) experience first hand.
* To wander without any particular aim or purpose.

==Notable historical periods of human exploration==
[[File:Orbe Europa.png|thumb|400px|Evolution of Western knowledge of the world]]

===Phoenician galley sailings===
The Phoenicians (1550 BCE–300 BCE) traded throughout the [[Mediterranean Sea]] and [[Asia Minor]] though many of their routes are still unknown today. The presence of tin in some Phoenician artifacts suggests that they may have traveled to [[United Kingdom|Britain]]. According to [[Virgil]]'s [[Aeneid]] and other ancient sources, the legendary Queen [[Dido]] was a Phoenician from [[Tyre, Lebanon|Tyre]] who sailed to [[North Africa]] and founded the city of [[Carthage]].

====Carthaginean exploration of Western Africa====
[[Hanno the Navigator]] (500 BC), a [[Ancient Carthage|Carthaginean]] navigator who explored the Western Coast of [[Africa]].

===Greek and Roman exploration of Northern Europe and Thule===
* [[Pytheas]] (4th century BC), a [[Ancient Greece|Greek]] explorer from [[Massalia]] ([[Marseille]]), was the first to circumnavigate [[Great Britain]], explore [[Germany]], and reach ''[[Thule]]'' (most commonly thought to be the [[Shetland Islands]] or [[Iceland]]).
* Under [[Augustus]], [[Ancient Rome|Romans]] reached and explored all the [[Baltic Sea]].

===Roman explorations===
;Africa exploration
The Romans [[Romans in sub-Saharan Africa|organized expeditions]] to cross the [[Sahara]] along five different routes:

*through the [[Western Sahara]], toward the [[Niger River]], near modern [[Timbuktu]]
*through the [[Tibesti Mountains]], toward [[Lake Chad]] and modern [[Nigeria]]
*up the [[Nile]] valley through [[Aegyptus|Egypt]], toward the [[Great Rift Valley]]
*along the western coast of Africa, toward the [[Sénégal River]]
*along the coast of the [[Red Sea]], toward the [[Horn of Africa]], and perhaps modern [[Zanzibar]].

All these expeditions were supported by legionaries and had mainly a commercial purpose. Only the one conducted by emperor [[Nero]] seemed to be a preparative for the conquest of [[Ethiopia]] or [[Nubia]]; in 62 AD, two legionaries [[Nero's exploration of the Nile|explored the sources of the Nile]].<ref>{{cite book |url=https://books.google.com/books?id=8OgVKbssrT0C&pg=PT364 |title=A Companion to the Neronian Age |first1=Emma |last1=Buckley |first2=Martin |last2=Dinter |publisher=[[John Wiley & Sons]] |date=3 May 2013 |page=364 |isbn=9781118316535}}</ref>

One of the main objectives of the explorations was to locate and obtain [[gold]], using [[camel]]s to transport it overland back to Roman provinces on the Mediterranean coast.<ref>Roth, Jonathan 2002. ''The Roman Army in Tripolitana and Gold Trade with Sub-Saharan Africa''. APA Annual Convention. New Orleans.</ref>

The explorations near the African western and eastern coasts were supported by Roman ships and deeply related to the naval commerce (mainly toward the [[Indian Ocean]]).
The Romans also organized [[Germanic–Roman contacts|several explorations into Northern Europe]], and [[Sino-Roman relations|explored as far as China]] in [[Asia]].

;30 BC – 640 AD: With the acquisition of Ptolemaic Egypt, [[Indo-Roman trade relations|the Romans begin trading with India]]. The Romans now have a direct connection to the [[spice trade]], which the Egyptians had established beginning in 118 BC.

;100–166 AD: [[Sino-Roman relations]] begin. [[Ptolemy]] [[Geography (Ptolemy)|writes]] of the [[Golden Chersonese]] (i.e. [[Malay Peninsula]]) and the trade port of Kattigara, now identified as [[Óc Eo]] in northern [[Vietnam]], then part of [[Jiaozhou (region)|Jiaozhou]], a province of the Chinese [[Han dynasty|Han Empire]]. The [[Twenty-Four Histories|Chinese historical texts]] describe Roman embassies, from a land they called ''[[Daqin]]''.

;2nd century: Roman traders reach [[Siam]], [[Cambodia]], [[Sumatra]], and [[Java]].

;161: An embassy from Roman Emperor [[Antoninus Pius]] or his successor [[Marcus Aurelius]] reaches Chinese [[Emperor Huan of Han]] at [[Luoyang]].

;226: A Roman diplomat or merchant lands in northern Vietnam and visits [[Nanjing]], China and the court of [[Sun Quan]], ruler of [[Eastern Wu]].

===Chinese exploration of Central Asia===
During the 2nd century BC, the [[Han dynasty]] explored much of the Eastern Northern Hemisphere. Starting in 139 BC, the Han diplomat [[Zhang Qian]] traveled west in an unsuccessful attempt to secure an alliance with the Da [[Yuezhi]] against the [[Xiongnu]] (the Yuezhi had been evicted from [[Gansu]] by the Xiongnu in 177 BC); however, Zhang's travels discovered entire countries which the Chinese were unaware of, including the [[Hellenistic civilization|remnants of the conquests]] of [[Alexander the Great]] (r. 336–323 BC).{{sfnm|di Cosmo|2002|1pp=247–249|Yü|1986|2p=407|Torday|1997|3p=104|4a1=Morton|4a2=Lewis|4y=2005|4pp=54–55}} When Zhang returned to China in 125 BC, he reported on his visits to [[Dayuan]] ([[Fergana]]), [[Kangju]] ([[Sogdia]]), and [[Daxia]] ([[Bactria]], formerly the [[Greco-Bactrian Kingdom]] which had just been subjugated by the Da Yuezhi).{{sfn|Torday|1997|pp=105–106}} Zhang described Dayuan and Daxia as agricultural and urban countries like China, and although he did not venture there, described Shendu (the [[Indus River]] valley of Northwestern India) and Anxi ([[Parthian Empire|Parthian]] territories) further west.{{sfn|Torday|1997|pp=108–112}}

===Viking Age===
[[File:Vikings-Voyages.png|thumb|Viking settlements and voyages]]

From about 800 AD to 1040 AD, the [[Vikings]] explored Iceland and much of the Western Northern Hemisphere via rivers and oceans. For example, it is known that the [[Norway|Norwegian]] [[Viking]] explorer, [[Erik the Red]] (950–1003), sailed to and settled in [[Greenland]] after being expelled from [[Iceland]], while his son, the [[Iceland]]ic explorer [[Leif Erikson]] (980–1020), reached [[Newfoundland]] and the nearby North American coast, and is believed to be the first [[Europe]]an to land in [[North America]].

===Polynesian Age===
[[File:Chronological dispersal of Austronesian people across the Pacific.svg|thumb|[[Austronesian peoples|Austronesian]] expansion map]]

[[Polynesians]] were a maritime people, who populated and explored the central and [[Oceania|south Pacific]] for around 5,000 years, up to about 1280 when they discovered [[New Zealand]]. The key invention to their exploration was the [[outrigger canoe]], which provided a swift and stable platform for carrying goods and people. Based on limited evidence, it is thought that the voyage to New Zealand was deliberate. It is unknown if one or more boats went to New Zealand, or the type of boat, or the names of those who migrated. 2011 studies at [[Wairau Bar]] in New Zealand show a high probability that one origin was Ruahine Island in the [[Society Islands]]. Polynesians may have used the prevailing north easterly [[trade winds]] to reach New Zealand in about three weeks. The Cook Islands are in direct line along the migration path and may have been an intermediate stopping point. There are cultural and language similarities between [[Cook Islanders]] and New Zealand [[Māori people|Māori]]. Early Māori had different legends of their origins, but the stories were misunderstood and reinterpreted in confused written accounts by early European historians in New Zealand trying to present a coherent pattern of Māori settlement in New Zealand.

Mathematical modelling based on DNA [[Identity by descent|genome studies]], using [[state of the art]] techniques, have shown that a large number of Polynesian migrants (100–200), including women, arrived in New Zealand around the same time, in about 1280. [[Otago University]] studies have tried to link distinctive DNA teeth patterns, which show special dietary influence, with places in or nearby the [[Society Islands]].<ref>Otago University. Wairau Bar Studies 2011. Dr L. Matisoo-Smith.</ref>

===Chinese exploration of the Indian Ocean===
The Chinese explorer, [[Wang Dayuan]] ([[Floruit|fl.]] 1311–1350) made two major trips by ship to the Indian Ocean. During 1328–1333, he sailed along the [[South China Sea]] and visited many places in [[Southeast Asia]] and reached as far as [[South Asia]], landing in [[Sri Lanka]] and [[India]], and he even went to [[Australia]]. Then in 1334–1339, he visited [[North Africa]] and [[East Africa]]. Later, the Chinese admiral [[Zheng He]] (1371–1433) made [[Ming treasure voyages|seven voyages]] to [[Arabia]], [[East Africa]], [[India]], [[Indonesia]], and [[Thailand]].

===European Age of Discovery===
[[File:Viajes_de_colon_en.svg|thumb|300px|The transatlantic [[voyages of Christopher Columbus]]]]

The [[Age of Discovery]], also known as the Age of Exploration, is one of the most important periods of geographical exploration in human history. It started in the early 15th century and lasted until the 17th century. In that period, Europeans discovered and/or explored vast areas of the Americas, Africa, Asia, and Oceania. [[Portuguese Empire|Portugal]] and [[Spanish Empire|Spain]] dominated the first stages of exploration, while other European nations followed, such as [[English overseas possessions|England]], [[French colonial empire|France]], and the [[Dutch colonial empire|Netherlands]].

[[File:Map of Portuguese Carreira da India.gif|300px|thumb|Outward and return voyages of the [[Portuguese India Armadas|Portuguese India run]] in the Atlantic and the Indian oceans, with the [[North Atlantic Gyre]] (''[[volta do mar]]'') picked up by [[Henry the Navigator|Henry]]'s navigators, and the outward route of the South Atlantic westerlies that [[Bartolomeu Dias]] discovered in 1488, followed and explored by the expeditions of [[Vasco da Gama]] and [[Pedro Álvares Cabral]].]]
Important explorations during this period went to a number of continents and regions around the globe. In Africa, important explorers of this period include [[Diogo Cão]] (1452–1486), who discovered and ascended the [[Congo River]] and reached the coasts of present-day [[Angola]] and [[Namibia]]; and [[Bartolomeu Dias]] (1450–1500), the first European to reach the [[Cape of Good Hope]] and other parts of the [[South Africa]]n coast.

Explorers of routes from Europe towards Asia, the Indian Ocean, and the Pacific Ocean, include [[Vasco da Gama]] (1460–1524), a navigator who made the first trip from Europe to India and back by the Cape of Good Hope, discovering the ocean route to the [[East]]; [[Pedro Álvares Cabral]] (1467/1468–1520), who, following the path of Vasco da Gama, claimed [[Brazil]] and led the first expedition that linked Europe, Africa, America, and Asia; [[Diogo Dias]], who discovered the eastern coast of [[Madagascar]] and rounded the corner of Africa; explorers such as [[Diogo Fernandes Pereira]] and [[Pedro Mascarenhas]] (1470–1555), among others, who discovered and mapped the [[Mascarene Islands]] and other archipelagos.

[[António de Abreu]] (1480–1514) and [[Francisco Serrão]] (14??–1521) led the first direct European fleet into the Pacific Ocean (on its western edges) and through the [[Sunda Islands]], reaching the [[Maluku Islands|Moluccas]]. [[Andrés de Urdaneta]] (1498–1568) discovered the maritime route from Asia to the Americas.

In the Pacific Ocean, [[Jorge de Menezes]] (1498–1537) reached [[New Guinea]] while [[Loaísa expedition|García Jofre de Loaísa]] (1490–1526) reached the [[Marshall Islands]].

;Discovery of America
Explorations of the Americas began with the initial discovery of America by [[Christopher Columbus]] (1451–1506), who led a [[Crown of Castile|Castilian]] ([[Spanish Empire|Spanish]]) expedition across the Atlantic, [[Voyages of Christopher Columbus|discovering America]]. After the discovery of America by Columbus, a number of important expeditions were sent out to explore the Western Hemisphere. This included [[Juan Ponce de León]] (1474–1521), who discovered and mapped the coast of [[Florida]]; [[Vasco Núñez de Balboa]] (1475–1519), who was the first European to view the Pacific Ocean from American shores (after crossing the [[Isthmus of Panama]]) confirming that America was a separate continent from Asia; [[Aleixo Garcia]] (14??–1527), who explored the territories of present-day southern Brazil, [[Paraguay]] and [[Bolivia]], crossing the [[Gran Chaco|Chaco]] and reaching the [[Andes]] (near [[Sucre]]).

[[Álvar Núñez Cabeza de Vaca]] (1490–1558) discovered the [[Mississippi River]] and was the first European to sail the [[Gulf of Mexico]] and cross [[Texas]]. [[Jacques Cartier]] (1491–1557) drew the first maps of part of central and maritime Canada; [[Francisco Vázquez de Coronado]] (1510–1554) discovered the [[Grand Canyon]] and the [[Colorado River]]; [[Francisco de Orellana]] (1511–1546) was the first European to navigate the length of the [[Amazon River]].

;Further explorations
[[File:Cook Three Voyages 59.png|thumb|300px|The routes of Captain [[James Cook]]'s voyages. The first voyage is shown in '''<span style="color:red;">red</span>''', second voyage in '''<span style="color:green;">green</span>''', and third voyage in '''<span style="color:blue;">blue</span>'''.]]

[[Ferdinand Magellan]] (1480–1521), was the first navigator to cross the Pacific Ocean, discovering the [[Strait of Magellan]], the [[Tuamotus]] and [[Mariana Islands]], and achieving a nearly complete [[circumnavigation]] of the Earth, in multiple voyages, for the first time. [[Juan Sebastián Elcano]] (1476–1526), completed the first [[Timeline of Magellan's circumnavigation|global circumnavigation]].

In the second half of the 16th century and the 17th century exploration of Asia and the Pacific Ocean continued with explorers such as [[Andrés de Urdaneta]] (1498–1568), who discovered the maritime route from Asia to the Americas; [[Pedro Fernandes de Queirós]] (1565–1614), who discovered the [[Pitcairn Islands]] and the [[Vanuatu]] archipelago; [[Álvaro de Mendaña de Neira]] (1542–1595), who discovered the [[Tuvalu]] archipelago, the [[Marquesas Islands|Marquesas]], the [[Solomon Islands|Solomons]], and [[Wake Island]].

Explorers of Australia included [[Willem Janszoon]] (1570–1630), who made the first recorded European landing in Australia; [[Yñigo Ortiz de Retez]], who discovered and reached eastern and northern [[New Guinea]]; [[Luis Váez de Torres]] (1565–1613), who discovered the [[Torres Strait]] between [[Australia]] and [[New Guinea]]; [[Abel Tasman]] (1603–1659), who explored North Australia, discovered [[Tasmania]], [[New Zealand]], and [[Tongatapu]].

In North America, major explorers included [[Henry Hudson]] (1565–1611), who explored the [[Hudson Bay]] in Canada; [[Samuel de Champlain]] (1574–1635), who explored [[St. Lawrence River]] and the [[Great Lakes]] (in Canada and northern United States); and [[René-Robert Cavelier, Sieur de La Salle]] (1643–1687), who explored the Great Lakes region of the United States and Canada, and the entire length of the Mississippi River.

===Late modern period===
{{see also|Deep-sea exploration|Late modern period}}
[[File:Carte Lewis-Clark Expedition-en.png|thumb|Route of the [[Lewis and Clark Expedition]]]]

Long after the Age of Discovery, other explorers "completed" the world map, such as various [[Russian Empire|Russian]] explorers, reaching the [[Siberia]]n Pacific coast and the [[Bering Strait]], at the extreme edge of Asia and [[Alaska]] (North America); [[Vitus Bering]] (1681–1741) who in the service of the Russian Navy, explored the Bering Strait, the [[Bering Sea]], the North American coast of Alaska, and some other northern areas of the Pacific Ocean; and [[James Cook]], who explored the east coast of Australia, the [[Hawaiian Islands]], and circumnavigated [[Antarctica]].

There were still significant explorations which occurred well into the [[late modern period]]. This includes the [[Lewis and Clark Expedition]] (1804–1806), an overland expedition dispatched by President [[Thomas Jefferson]] to explore the newly acquired Louisiana Purchase and to find an interior aquatic route to the Pacific Ocean, along with other objectives to examine the flora and fauna of the continent. In 1818, the British researcher [[John Ross (Royal Navy officer)|John Ross]] was the first to find that the deep sea is inhabited by life when catching [[jellyfish]] and [[worm]]s in about {{convert|2000|m|ft|abbr=on|0}} depth with a special device.{{Clarify|reason=What kind of special device?|date=January 2023}} The [[United States Exploring Expedition]] (1838–1842) was an expedition sent by President [[Andrew Jackson]], in order to survey the Pacific Ocean and surrounding lands.

The extreme conditions in the deep sea require elaborate methods and technologies to endure them. In the 20th century, deep-sea exploration advanced considerably through a series of technological inventions, ranging from the [[sonar]] system, which can detect the presence of solid objects underwater through the use of reflected sound, to manned [[Deep-submergence vehicle|deep-diving submersibles]]. In 1960, [[Jacques Piccard]] and [[United States Navy]] Lieutenant [[Don Walsh|Donald Walsh]] descended in the [[bathyscaphe]] [[Bathyscaphe Trieste|''Trieste'']] into the deepest part of the world's oceans, the [[Mariana Trench]].<ref name="independent1">{{cite news |url=https://www.independent.co.uk/news/obituaries/jacques-piccard-oceanographer-and-pioneer-of-deepsea-exploration-992032.html |title=Jacques Piccard: Oceanographer and pioneer of deep-sea exploration – Obituaries, News |work=[[The Independent]] |date= 2008-11-05 |access-date=2010-09-17 |location=London}}</ref> In 2018, {{ship||DSV Limiting Factor}}, piloted by [[Victor Vescovo]], completed the first mission to the deepest point of the Atlantic Ocean, diving {{Convert|8,375|m|ft|abbr=on}} below the ocean surface to the base of the [[Puerto Rico Trench]].<ref>{{Cite news |url=https://www.theguardian.com/science/2018/dec/22/wall-street-trader-reaches-bottom-of-atlantic-in-bid-to-conquer-five-oceans |title=Wall Street trader reaches bottom of Atlantic in bid to conquer five oceans |last=Neate |first=Rupert |date=2018-12-22 |work=[[The Guardian]] |access-date=2019-06-02 |language=en-GB |issn=0261-3077}}</ref> With the advent of satellite imagery and aviation, broad scale exploration of the surface of [[Earth]] has largely ceased, however the culture of many disconnected tribes still remain undocumented and left to be explored, and the details of more inaccessible ecosystems remains undescribed. Urban exploration is the exploration of manmade structures, usually abandoned ruins or hidden components of the manmade environment.

===Space age===
{{main|Space exploration}}

[[Space exploration]] started in the 20th century with the invention of exo-atmospheric [[rocket]]s. This has given humans the opportunity to travel to the [[Moon]], and to send robotic explorers to other [[planet]]s and far beyond.

Both of the [[Voyager program|Voyager probes]] have left the [[Solar System]], bearing imprinted gold discs with multiple data types.

==Underwater exploration==
{{main|Underwater exploration}}

===Objectives===
The scope of underwater exploration includes the distribution and variety of marine and aquatic life, measurement of the geographical distribution of the chemical and physical properties, including movement of the water, and the geophysical, geological and topographical features of the Earth's crust where it is covered by water.<ref name="Britannica" />

Systematic, targeted exploration is the most effective method to increase understanding of the ocean and other underwater regions, so they can be effectively managed, conserved, regulated, and their resources discovered, accessed, and used. The ocean covers approximately 70% of Earth’s surface and has a critical role in supporting life on the planet but knowledge and understanding of the ocean remains limited due to difficulty and cost of access.<ref name="NOAA" />

The distinction between exploration, survey, and other research is somewhat blurred, and one way of looking at it is to consider the baseline surveys and research as exploration, as previously unknown information is gathered. Updating and refining the data is less exploratory in nature, but may still be exploration for the people involved, in the sense that the experience is new to them.

===Status===
According to NOAA, as of January 2023: "More than eighty percent of our ocean is unmapped, unobserved, and unexplored."  Less than 10% of the ocean, including about 35% of the ocean and coastal waters of the United States, have been mapped in any detail using sonar technology.<ref name="NOAA/NOS" /> According to GEBCO 2019 data, less than 18% of the deep ocean bed has been mapped using direct measurement and about 50% of coastal waters were not yet surveyed.<ref name="IHO DCDB" />

Most of the data used to create global seabed maps are approximate depths derived from satellite gravity measurements and sea surface heights which are affected by the shape and mass distribution of the seabed. This method of approximation only provides low resolution information on large topographical features, and can miss significant features.<ref name="NCEI" />

==See also==
{{Columns-list|<!-- much of this should eventually become part of this article, linked inline, and removed from here. -->
* {{annotated link|Early human migrations}}
* {{annotated link|Timeline of European exploration}}
* {{annotated link|Timeline of maritime migration and exploration}}
* {{annotated link|European exploration of Africa}}
* {{annotated link|List of explorations}}
* {{annotated link|List of explorers}}
* {{annotated link|List of maritime explorers}}
* {{annotated link|List of underwater explorers}}
}}

==References==

===Citations===
{{reflist|refs=

<ref name="Britannica" >{{cite book|last1=Baker |first1=D. James |last2=Rechnitzer |first2=Andreas B. |chapter=Undersea exploration |title=Encyclopedia Britannica |chapter-url=https://www.britannica.com/technology/undersea-exploration |access-date=29 December 2022 }}</ref>

<ref name="IHO DCDB" >{{cite web |url=https://www.ncei.noaa.gov/iho-data-centre-digital-bathymetry |title=IHO Data Centre for Digital Bathymetry (DCDB) |website=www.ngdc.noaa.gov |publisher=NOAA |access-date=10 January 2023 }}</ref>

<ref name="NCEI" >{{cite web |url=https://www.ncei.noaa.gov/news/seabed-2030-map-gaps |title=Seabed 2030: Map the Gaps |website=www.ncei.noaa.gov |access-date=10 January 2023 |date=29 June 2022 }}</ref>

<ref name="NOAA" >{{cite web |url=https://oceanexplorer.noaa.gov/backmatter/whatisexploration.html |title=Why do we explore the ocean? |website=oceanexplorer.noaa.gov |publisher=NOAA |access-date=6 January 2023 }}</ref>

<ref name="NOAA/NOS" >{{cite web |url=https://oceanservice.noaa.gov/facts/exploration.html |title=How much of the ocean have we explored? |website=oceanservice.noaa.gov |access-date=6 January 2023 }}</ref>

}}

===Sources===
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* {{cite book |last=Groh |first=Arnold |title=Research Methods in Indigenous Contexts |year=2018 |publisher=Springer |location=New York |isbn=978-3-319-72774-5}}
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* {{cite book |last=Petringa |first=Maria |title=Brazzà, a Life for Africa |year=2006 |publisher=[[AuthorHouse]] |location=Bloomington, IN |isbn=1-4259-1198-6 |oclc=74651678}}
* {{cite book |last=Torday |first=Laszlo |year=1997 |title=Mounted Archers: The Beginnings of Central Asian History |location=Durham |publisher=The Durham Academic Press |isbn=978-1-900838-03-0}}
* {{cite book |last=Yü |first=Ying-shih |year=1986 |chapter=Han Foreign Relations |title=The Cambridge History of China |volume=I: the Ch'in and Han Empires, 221 B.C.–A.D. 220 |pages=377–462 |editor1-first=Denis |editor1-last=Twitchett |editor2-first=Michael |editor2-last=Loewe |location=Cambridge |publisher=[[Cambridge University Press]] |isbn=978-0-521-24327-8}}

==Further reading==
* {{Cite book |last=Chaudhuri |first=K. N. |url=https://books.google.com/books?id=dGGTYYA1uEoC |title=The Times Atlas of World Exploration: 3,000 Years of Exploring, Explorers, and Mapmaking |date=1991 |publisher=[[HarperCollins]] Publishers |isbn=978-0-06-270032-2 |language=en}}
* {{Cite book |editor-last=Buiisseret |editor-first=David |last= |first= |url=https://books.google.com/books?id=xyAjAQAAIAAJ |title=The Oxford Companion to World Exploration |date=2007 |publisher=[[Oxford University Press]] |isbn=978-0-19-514922-7 |language=en}}

==External links==
{{wikiquote}}
{{Wiktionary}}
* [https://web.archive.org/web/20071221024705/http://www.nationalgeographic.com/field/explorers ''National Geographic'' Explorer Program]
* [http://www.oceanexplorer.noaa.gov NOAA Ocean Explorer] – provides public access to current information on a series of NOAA scientific and educational explorations and activities in the marine environment
* [https://web.archive.org/web/20180830120838/http://explore.noaa.gov/ NOAA Office of Ocean Exploration and Research] – formed by the merger of NOAA's Undersea Research Program (NURP) and the Office of Ocean Exploration (OE)

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[[Category:Adventure]]
[[Category:Exploration]]
[[Category:Historical eras]]
[[Category:World history]]