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<span>Operation</span> </div> </a> <ul id="toc-Operation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Accuracy" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Accuracy"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Accuracy</span> </div> </a> <ul id="toc-Accuracy-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Variations" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Variations"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Variations</span> </div> </a> <button aria-controls="toc-Variations-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Variations subsection</span> </button> <ul id="toc-Variations-sublist" class="vector-toc-list"> <li id="toc-European_DGPS_Network" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#European_DGPS_Network"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>European DGPS Network</span> </div> </a> <ul id="toc-European_DGPS_Network-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-United_States_NDGPS" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#United_States_NDGPS"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>United States NDGPS</span> </div> </a> <ul id="toc-United_States_NDGPS-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Canadian_DGPS" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Canadian_DGPS"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Canadian DGPS</span> </div> </a> <ul id="toc-Canadian_DGPS-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Australia" 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Available in 22 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-22" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">22 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/GPS_diferencial" title="GPS diferencial – Catalan" lang="ca" hreflang="ca" data-title="GPS diferencial" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Diferenci%C3%A1ln%C3%AD_GPS" title="Diferenciální GPS – Czech" lang="cs" hreflang="cs" data-title="Diferenciální GPS" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Differential_Global_Positioning_System" title="Differential Global Positioning System – German" lang="de" hreflang="de" data-title="Differential Global Positioning System" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/GPS_diferencial" title="GPS diferencial – Spanish" lang="es" hreflang="es" data-title="GPS diferencial" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%AC%DB%8C%E2%80%8C%D9%BE%DB%8C%E2%80%8C%D8%A7%D8%B3_%D8%AA%D9%81%D8%A7%D8%B6%D9%84%DB%8C" title="جی‌پی‌اس تفاضلی – Persian" lang="fa" hreflang="fa" data-title="جی‌پی‌اس تفاضلی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/GPS_diff%C3%A9rentiel" title="GPS différentiel – French" lang="fr" hreflang="fr" data-title="GPS différentiel" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/GPS_differenziale" title="GPS differenziale – Italian" lang="it" hreflang="it" data-title="GPS differenziale" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/DGPS" title="DGPS – Hebrew" lang="he" hreflang="he" data-title="DGPS" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/DGPS" title="DGPS – Latvian" lang="lv" hreflang="lv" data-title="DGPS" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/DGPS" title="DGPS – Dutch" lang="nl" hreflang="nl" data-title="DGPS" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%83%87%E3%82%A3%E3%83%95%E3%82%A1%E3%83%AC%E3%83%B3%E3%82%B7%E3%83%A3%E3%83%ABGPS" title="ディファレンシャルGPS – Japanese" lang="ja" hreflang="ja" data-title="ディファレンシャルGPS" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/DGPS" title="DGPS – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="DGPS" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/DGPS" title="DGPS – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="DGPS" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/R%C3%B3%C5%BCnicowy_GPS" title="Różnicowy GPS – Polish" lang="pl" hreflang="pl" data-title="Różnicowy GPS" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/GPS_diferencial" title="GPS diferencial – Portuguese" lang="pt" hreflang="pt" data-title="GPS diferencial" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/Differential_GPS" title="Differential GPS – Russian" lang="ru" hreflang="ru" data-title="Differential GPS" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Differentiaalinen_GPS" title="Differentiaalinen GPS – Finnish" lang="fi" hreflang="fi" data-title="Differentiaalinen GPS" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Differentiell_GPS" title="Differentiell GPS – Swedish" lang="sv" hreflang="sv" data-title="Differentiell GPS" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Ayr%C4%B1msal_GPS" title="Ayrımsal GPS – Turkish" lang="tr" hreflang="tr" data-title="Ayrımsal GPS" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/DGPS" title="DGPS – Ukrainian" lang="uk" hreflang="uk" data-title="DGPS" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/H%E1%BB%87_th%E1%BB%91ng_%C4%90%E1%BB%8Bnh_v%E1%BB%8B_To%C3%A0n_c%E1%BA%A7u_vi_sai" title="Hệ thống Định vị Toàn cầu vi sai – Vietnamese" lang="vi" hreflang="vi" data-title="Hệ thống Định vị Toàn cầu vi sai" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E5%B7%AE%E5%88%86%E5%85%A8%E7%90%83%E5%AE%9A%E4%BD%8D%E7%B3%BB%E7%BB%9F" title="差分全球定位系统 – Chinese" lang="zh" hreflang="zh" data-title="差分全球定位系统" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q779225#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a 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data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Enhancement to the Global Positioning System providing improved accuracy</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Claas_Baseline_HD.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/22/Claas_Baseline_HD.jpg/220px-Claas_Baseline_HD.jpg" decoding="async" width="220" height="330" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/22/Claas_Baseline_HD.jpg/330px-Claas_Baseline_HD.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/22/Claas_Baseline_HD.jpg/440px-Claas_Baseline_HD.jpg 2x" data-file-width="1333" data-file-height="2000" /></a><figcaption>Transportable DGPS reference station <i>Baseline HD</i> by <a href="/wiki/CLAAS" class="mw-redirect" title="CLAAS">CLAAS</a> for use in satellite-assisted steering systems in modern agriculture</figcaption></figure> <p><b>Differential Global Positioning Systems</b> (<b>DGPSs</b>) supplement and enhance the positional data available from <a href="/wiki/Global_navigation_satellite_system" class="mw-redirect" title="Global navigation satellite system">global navigation satellite systems</a> (GNSSs). A DGPS can increase accuracy of positional data by about a thousandfold, from approximately 15 metres (49 ft) to <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style>1–3 centimetres (<span class="frac"><span class="num">1</span>⁄<span class="den">2</span></span>–<span class="frac">1<span class="sr-only">+</span><span class="num">1</span>⁄<span class="den">4</span></span> in).<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>DGPSs consist of networks of fixed position, ground-based reference stations. Each reference station calculates the difference between its highly accurate known position and its less accurate satellite-derived position. The stations broadcast this data locally—typically using ground-based transmitters of shorter range. Non-fixed (mobile) receivers use it to correct their position by the same amount, thereby improving their accuracy. </p><p>The <a href="/wiki/United_States_Coast_Guard" title="United States Coast Guard">United States Coast Guard</a> (USCG) previously ran DGPS in the United States on <a href="/wiki/Longwave" title="Longwave">longwave</a> radio frequencies between <span class="hMeasure frequency"><span class="num">285</span> <span class="unit">kHz</span></span> and <span class="hMeasure frequency"><span class="num">325</span> <span class="unit">kHz</span></span> near major waterways and harbors. It was discontinued in March 2022.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The USCG's DGPS was known as NDGPS (Nationwide DGPS) and was jointly administered by the Coast Guard and the <a href="/wiki/United_States_Army_Corps_of_Engineers" title="United States Army Corps of Engineers">Army Corps of Engineers</a>. It consisted of broadcast sites located throughout the inland and coastal portions of the United States including Alaska, Hawaii and Puerto Rico. The <a href="/wiki/Canadian_Coast_Guard" title="Canadian Coast Guard">Canadian Coast Guard</a> (CCG)<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> also ran a separate DGPS system, but discontinued its use on December 15, 2022. Other countries have their own DGPS.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2023)">citation needed</span></a></i>]</sup> </p><p>A similar system which transmits corrections from orbiting satellites instead of ground-based transmitters is called a Wide-Area DGPS (WADGPS)<sup id="cite_ref-1991Kee_4-0" class="reference"><a href="#cite_note-1991Kee-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Satellite-based_augmentation_system" class="mw-redirect" title="Satellite-based augmentation system">satellite-based augmentation system</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=1" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When GPS was first being put into service, the US military was concerned about the possibility of enemy forces using the globally available GPS signals to guide their own weapon systems. Originally, the government thought the "coarse acquisition" (C/A) signal would give only about 100-<a href="/wiki/Metre" title="Metre">metre</a> (330 <a href="/wiki/Foot_(unit)" title="Foot (unit)">ft</a>) accuracy, but with improved receiver designs, the actual accuracy was 20 to 30 <a href="/wiki/Metre" title="Metre">metres</a> (66 to 98 <a href="/wiki/Foot_(unit)" title="Foot (unit)">ft</a>).<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Starting in March 1990,<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 11">: 11 </span></sup> to avoid providing such unexpected accuracy, the C/A signal transmitted on the L1 frequency (<span class="hMeasure frequency"><span class="num">1575.42</span> <span class="unit">MHz</span></span>) was deliberately degraded by offsetting its clock signal by a random amount, equivalent to about 100 <a href="/wiki/Metre" title="Metre">metres</a> (330 <a href="/wiki/Foot_(unit)" title="Foot (unit)">ft</a>) of distance. This technique, known as <i><a href="/wiki/Selective_Availability" class="mw-redirect" title="Selective Availability">Selective Availability</a></i>, or SA for short, seriously degraded the usefulness of the GPS signal for non-military users. More accurate guidance was possible for users of dual-frequency GPS receivers which also received the L2 frequency (<span class="hMeasure frequency"><span class="num">1227.6</span> <span class="unit">MHz</span></span>), but the L2 transmission, intended for military use, was encrypted and was available only to authorized users with the decryption keys. </p><p>This presented a problem for civilian users who relied upon ground-based <a href="/wiki/Radio_navigation" title="Radio navigation">radio navigation</a> systems such as <a href="/wiki/LORAN" title="LORAN">LORAN</a>, <a href="/wiki/VHF_omnidirectional_range" title="VHF omnidirectional range">VOR</a> and <a href="/wiki/Non-directional_beacon" title="Non-directional beacon">NDB</a> systems costing millions of dollars each year to maintain. The advent of a <a href="/wiki/Global_navigation_satellite_system" class="mw-redirect" title="Global navigation satellite system">global navigation satellite system</a> (GNSS) could provide greatly improved accuracy and performance at a fraction of the cost. The accuracy inherent in the SA however, was too poor to make this realistic. The military received multiple requests from the <a href="/wiki/Federal_Aviation_Administration" title="Federal Aviation Administration">Federal Aviation Administration (FAA)</a>, <a href="/wiki/United_States_Coast_Guard" title="United States Coast Guard">United States Coast Guard (USCG)</a> and <a href="/wiki/United_States_Department_of_Transportation" title="United States Department of Transportation">United States Department of Transportation (DOT)</a> to set SA aside to enable civilian use of GNSS, but remained steadfast in its objection on grounds of security. </p><p>Throughout the early to mid 1980s, a number of agencies worked to develop a solution to the SA "problem".<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Accuracy_dispute#Disputed_statement" title="Wikipedia:Accuracy dispute"><span title="The material near this tag is possibly inaccurate or nonfactual. (February 2012)">dubious</span></a> – <a href="/wiki/Talk:Differential_GPS#Dubious" title="Talk:Differential GPS">discuss</a></i>]</sup> Since the SA signal was changed slowly, the effect of its offset on positioning was relatively fixed – that is, if the offset was "100 meters to the east", that offset would be true over a relatively wide area. This suggested that broadcasting this offset to local GPS receivers could eliminate the effects of SA, resulting in measurements closer to GPS's theoretical performance, around 15 metres (49 ft). Additionally, another major source of errors in a GPS fix is due to transmission delays in the <a href="/wiki/Ionosphere" title="Ionosphere">ionosphere</a>, which could also be measured and corrected for in the broadcast. This offered an improvement to about 5 metres (16 ft) accuracy, more than enough for most civilian needs.<sup class="plainlinks nourlexpansion citation" id="ref_FAA_FS"><a class="external autonumber" href="https://en.wikipedia.org/wiki/Differential_GPS#endnote_FAA_FS">[1]</a></sup> </p><p>The US Coast Guard was one of the more aggressive proponents of the DGPS, experimenting with the system on an ever-wider basis throughout the late 1980s and early 1990s. These signals are broadcast on marine <a href="/wiki/Longwave" title="Longwave">longwave</a> frequencies, which could be received on existing <a href="/wiki/Radiotelephone" title="Radiotelephone">radiotelephones</a><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify"><span title="The text near this tag needs further explanation. (October 2019)">further explanation needed</span></a></i>]</sup> and fed into suitably equipped GPS receivers. Almost all major GPS vendors offered units with DGPS inputs, not only for the USCG signals, but also aviation units on either <a href="/wiki/VHF" class="mw-redirect" title="VHF">VHF</a> or commercial <a href="/wiki/AM_radio" class="mw-redirect" title="AM radio">AM radio</a> bands. </p><p>"Production quality" DGPS signals began to be sent out on a limited basis in 1996, and the network was rapidly expanded to cover most US ports of call, as well as the <a href="/wiki/Saint_Lawrence_Seaway" class="mw-redirect" title="Saint Lawrence Seaway">Saint Lawrence Seaway</a> in partnership with the <a href="/wiki/Canadian_Coast_Guard" title="Canadian Coast Guard">Canadian Coast Guard</a>. Plans were put into place to expand the system across the US, but this would not be easy. The quality of the DGPS corrections generally fell with distance, and large transmitters capable of covering large areas tend to cluster near cities. This meant that lower-population areas, notably in the midwest and Alaska, would have little coverage by ground-based GPS. As of November 2013 the USCG's national DGPS consisted of 85 broadcast sites which provide dual coverage to almost the entire US coastline and inland navigable waterways including Alaska, Hawaii, and Puerto Rico. In addition the system provided single or dual coverage to a majority of the inland portion of United States.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Instead, the FAA (and others) started studying broadcasting the signals across the entire hemisphere from communications satellites in geostationary orbit. This led to the <a href="/wiki/Wide_Area_Augmentation_System" title="Wide Area Augmentation System">Wide Area Augmentation System</a> (WAAS) and similar systems, although these are generally not referred to as DGPS, or alternatively, "wide-area DGPS". WAAS offers accuracy similar to the USCG's ground-based DGPS networks, and there has been some argument that the latter will be turned off as WAAS becomes fully operational. </p><p>By the mid-1990s it was clear that the SA system was no longer useful in its intended role. DGPS would render it ineffective over the US, where it was considered most needed. Additionally, during the <a href="/wiki/Gulf_War" title="Gulf War">Gulf War</a> of 1990–1991 SA had been temporarily turned off because Allied troops were using commercial GPS receivers.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> This showed that leaving SA turned off could be useful to the United States.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> In 2000, an <a href="/wiki/Executive_order_(United_States)" class="mw-redirect" title="Executive order (United States)">executive order</a> by <a href="/wiki/President_of_the_United_States" title="President of the United States">President</a> <a href="/wiki/Bill_Clinton" title="Bill Clinton">Bill Clinton</a> turned it off permanently.<sup id="cite_ref-OSTP_10-0" class="reference"><a href="#cite_note-OSTP-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Nevertheless, by this point DGPS had evolved into a system for providing more accuracy than even a non-SA GPS signal could provide on its own. There are several other sources of error which share the same characteristics as SA in that they are the same over large areas and for "reasonable" amounts of time. These include the ionospheric effects mentioned earlier, as well as errors in the satellite position ephemeris data and <a href="/wiki/Clock_drift" title="Clock drift">clock drift</a> on the satellites. Depending on the amount of data being sent in the DGPS correction signal, correcting for these effects can reduce the error significantly, the best implementations offering accuracies of under 10 centimetres (3.9 in). </p><p>In addition to continued deployments of the USCG and FAA sponsored systems, a number of vendors have created commercial DGPS services, selling their signal (or receivers for it) to users who require better accuracy than the nominal 15 meters GPS offers. Almost all commercial GPS units, even hand-held units, now offer DGPS data inputs, and many also support WAAS directly. To some degree, a form of DGPS is now a natural part of most GPS operations. </p> <div class="mw-heading mw-heading2"><h2 id="Operation">Operation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=2" title="Edit section: Operation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:DGPS_Reference_Station.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c6/DGPS_Reference_Station.jpg/170px-DGPS_Reference_Station.jpg" decoding="async" width="170" height="202" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c6/DGPS_Reference_Station.jpg/255px-DGPS_Reference_Station.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c6/DGPS_Reference_Station.jpg/340px-DGPS_Reference_Station.jpg 2x" data-file-width="800" data-file-height="950" /></a><figcaption>DGPS Reference Station (<a href="/wiki/Choke_ring_antenna" title="Choke ring antenna">choke ring antenna</a>)</figcaption></figure> <p>A reference station calculates differential corrections for its own location and time. Users may be up to 200 nautical miles (370 km) from the station, however, and some of the compensated errors vary with space: specifically, satellite <a href="/wiki/Ephemeris" title="Ephemeris">ephemeris</a> errors and those introduced by <a href="/wiki/Ionosphere" title="Ionosphere">ionospheric</a> and <a href="/wiki/Troposphere" title="Troposphere">tropospheric</a> distortions. For this reason, the accuracy of DGPS decreases with distance from the reference station. The problem can be aggravated if the user and the station lack "inter visibility"—when they are unable to see the same satellites. </p> <div class="mw-heading mw-heading2"><h2 id="Accuracy">Accuracy</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=3" title="Edit section: Accuracy"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The United States <i>Federal Radionavigation Plan</i> and the <a href="/wiki/International_Association_of_Lighthouse_Authorities" class="mw-redirect" title="International Association of Lighthouse Authorities">IALA</a> <i>Recommendation on the Performance and Monitoring of DGNSS Services in the Band <span class="nowrap">283.5–325 kHz</span></i> cite the <a href="/wiki/United_States_Department_of_Transportation" title="United States Department of Transportation">United States Department of Transportation</a>'s 1993 estimated error growth of 0.67 <a href="/wiki/Grade_(slope)" title="Grade (slope)">metres per 100 kilometres</a> (3.5 <a href="/wiki/Grade_(slope)" title="Grade (slope)">ft/100 mi</a>) from the broadcast site <sup id="cite_ref-2001FederalRadionavigation_11-0" class="reference"><a href="#cite_note-2001FederalRadionavigation-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> but measurements of accuracy across the Atlantic, in Portugal, suggest a degradation of just 0.22 <a href="/wiki/Grade_(slope)" title="Grade (slope)">m/100 km</a> (1.2 <a href="/wiki/Grade_(slope)" title="Grade (slope)">ft/100 mi</a>).<sup id="cite_ref-2005Monteiro_12-0" class="reference"><a href="#cite_note-2005Monteiro-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Variations">Variations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=4" title="Edit section: Variations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>DGPS can refer to any type of Ground-Based Augmentation System (GBAS). There are many operational systems in use throughout the world, according to the US Coast Guard, 47 countries operate systems similar to the US NDGPS (Nationwide Differential Global Positioning System). A list can be found at the World DGPS Database for Dxers.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="European_DGPS_Network">European DGPS Network</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=5" title="Edit section: European DGPS Network"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>European DGPS network has been developed mainly by the Finnish and Swedish maritime administrations in order to improve safety in the archipelago between the two countries.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (August 2018)">citation needed</span></a></i>]</sup> </p><p>In the UK and Ireland, the system was implemented as a maritime navigation aid to fill the gap left by the demise of the <a href="/wiki/Decca_Navigator_System" title="Decca Navigator System">Decca Navigator System</a> in 2000. With a network of 12 transmitters sited around the coastline and three control stations, it was set up in 1998 by the countries' respective General Lighthouse Authorities (GLA) — <a href="/wiki/Trinity_House" title="Trinity House">Trinity House</a> covering <a href="/wiki/England" title="England">England</a>, <a href="/wiki/Wales" title="Wales">Wales</a> and the <a href="/wiki/Channel_Islands" title="Channel Islands">Channel Islands</a>, the <a href="/wiki/Northern_Lighthouse_Board" title="Northern Lighthouse Board">Northern Lighthouse Board</a> covering <a href="/wiki/Scotland" title="Scotland">Scotland</a> and the <a href="/wiki/Isle_of_Man" title="Isle of Man">Isle of Man</a> and the <a href="/wiki/Commissioners_of_Irish_Lights" title="Commissioners of Irish Lights">Commissioners of Irish Lights</a>, covering the whole of <a href="/wiki/Ireland" title="Ireland">Ireland</a>. Transmitting on the 300-kHz band, the system underwent testing and two additional transmitters were added before the system was declared operational in 2002.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p><p>Effective Solutions provides details and a map of European Differential Beacon Transmitters.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="United_States_NDGPS">United States NDGPS</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=6" title="Edit section: United States NDGPS"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/United_States_Department_of_Transportation" title="United States Department of Transportation">United States Department of Transportation</a>, in conjunction with the <a href="/wiki/Federal_Highway_Administration" title="Federal Highway Administration">Federal Highway Administration</a>, the <a href="/wiki/Federal_Railroad_Administration" title="Federal Railroad Administration">Federal Railroad Administration</a> and the <a href="/wiki/U.S._National_Geodetic_Survey" title="U.S. National Geodetic Survey">National Geodetic Survey</a> appointed the <a href="/wiki/United_States_Coast_Guard" title="United States Coast Guard">United States Coast Guard</a> as the maintaining agency for the U.S. Nationwide DGPS network (NDGPS). The system is an expansion of the previous Maritime Differential GPS (MDGPS), which the Coast Guard began in the late 1980s and completed in March 1999. MDGPS covered only coastal waters, the Great Lakes, and the Mississippi River inland waterways, while NDGPS expands this to include complete coverage of the continental United States.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> The centralized Command and Control unit is the USCG Navigation Center, based in Alexandria, VA.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> There are currently 85 NDGPS sites in the US network, administered by the U.S. Department of Homeland Security Navigation Center. </p><p>In 2015, the USCG and the <a href="/wiki/United_States_Army_Corps_of_Engineers" title="United States Army Corps of Engineers">United States Army Corps of Engineers</a> (USACE) sought comments on a planned phasing-out of the U.S. DGPS.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> In response to the comments received, a subsequent 2016 Federal Register notice announced that 46 stations would remain in service and "available to users in the maritime and coastal regions".<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> In spite of this decision, USACE decommissioned its remaining 7 sites and, in March 2018, the USCG announced that it would decommission its remaining stations by 2020.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> As of June 2020, all NDGPS service has been discontinued as it is no longer deemed a necessity owing to the removal of selective availability in 2000<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> and also the introduction of <a href="/wiki/GPS_satellite_blocks#Block_III_satellites" title="GPS satellite blocks">newer generation of GPS satellites</a>.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Canadian_DGPS">Canadian DGPS</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=7" title="Edit section: Canadian DGPS"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Canadian system was similar to the US system and was primarily for maritime usage covering the Atlantic and Pacific coast as well as the <a href="/wiki/Great_Lakes" title="Great Lakes">Great Lakes</a> and <a href="/wiki/Saint_Lawrence_Seaway" class="mw-redirect" title="Saint Lawrence Seaway">Saint Lawrence Seaway</a>. It was discontinued as a service December 15, 2022.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Australia">Australia</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=8" title="Edit section: Australia"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Australia runs three DGPSes: one is mainly for marine navigation, broadcasting its signal on the long-wave band;<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> another is used for land surveys and land navigation, and has corrections broadcast on the Commercial FM radio band. The third at Sydney airport is currently undergoing testing for precision landing of aircraft (2011), as a backup to the <a href="/wiki/Instrument_Landing_System" class="mw-redirect" title="Instrument Landing System">Instrument Landing System</a> at least until 2015. It is called the <a href="/wiki/Ground_Based_Augmentation_System" class="mw-redirect" title="Ground Based Augmentation System">Ground Based Augmentation System</a>. Corrections to aircraft position are broadcast via the aviation VHF band. </p><p>The marine DGPS service of 16 ground stations covering the Australian coast was discontinued effective July 1, 2020.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> Improved multichannel GPS capabilities, and signal sources from multiple providers (GPS, <a href="/wiki/GLONASS" title="GLONASS">GLONASS</a>, <a href="/wiki/Galileo_(satellite_navigation)" title="Galileo (satellite navigation)">Galileo</a> and <a href="/wiki/BeiDou" title="BeiDou">BeiDou</a>) was cited as providing better navigational accuracy than could be obtained from GPS + DGPS. An Australian Satellite-Based Augmentation System (SBAS), the Southern Positioning Augmentation Network (SouthPAN) offers higher accuracy positioning for GNSS users. <sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Post-processing">Post-processing</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=9" title="Edit section: Post-processing"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Post-processing is used in Differential GPS to obtain precise positions of unknown points by relating them to known points such as <a href="/wiki/Survey_marker" title="Survey marker">survey markers</a>. </p><p>The <a href="/wiki/GPS" class="mw-redirect" title="GPS">GPS</a> measurements are usually stored in <a href="/wiki/Computer_memory" title="Computer memory">computer memory</a> in the GPS receivers, and are subsequently transferred to a computer running the GPS post-processing software. The software computes <a href="/wiki/Baseline_(surveying)" title="Baseline (surveying)">baselines</a> using simultaneous measurement data from two or more GPS receivers. </p><p>The baselines represent a three-dimensional line drawn between the two points occupied by each pair of GPS antennas. The post-processed measurements allow more precise positioning, because most GPS errors affect each receiver nearly equally, and therefore can be cancelled out in the calculations. </p><p>Differential GPS measurements can also be computed in real time by some GPS receivers if they receive a correction signal using a separate radio receiver, for example in <a href="/wiki/Real_Time_Kinematic" class="mw-redirect" title="Real Time Kinematic">Real Time Kinematic</a> (RTK) <a href="/wiki/Surveying" title="Surveying">surveying</a> or <a href="/wiki/Navigation" title="Navigation">navigation</a>. </p><p>The improvement of GPS positioning doesn't require simultaneous measurements of two or more receivers in any case, but can also be done by special use of a <i>single</i> device. In the 1990s when even handheld receivers were quite expensive, some methods of quasi-differential GPS were developed, using the receiver in quick turns of positions or loops of 3-10 <a href="/wiki/Benchmark_(surveying)" title="Benchmark (surveying)">survey points</a>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (April 2021)">citation needed</span></a></i>]</sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=10" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/RTCM_SC-104" title="RTCM SC-104">RTCM SC-104</a> - a standard for transferring dGPS data to a GPS receiver</li> <li><a href="/wiki/Assisted_GPS" class="mw-redirect" title="Assisted GPS">Assisted GPS</a> (A-GPS) - System used primarily in GPS-equipped cellular devices to improve start-up performance</li> <li><a href="/wiki/GNSS_augmentation" title="GNSS augmentation">GNSS augmentation</a></li> <li><a href="/wiki/GNSS_enhancement" title="GNSS enhancement">GNSS enhancement</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=11" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://zentrale-stelle-sapos.de/wp-content/uploads/2020/09/SAPOS-Broschuere-2015-eng.pdf">"Satellite Positioning Service of the Official German Surveying and Mapping (SAPOS) Brochure"</a> <span 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Retrieved <span class="nowrap">2020-09-20</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Australia%27s+differential+global+positioning+system&rft.pub=Australian+Maritime+Safety+Authority&rft_id=https%3A%2F%2Fwww.amsa.gov.au%2Fsafety-navigation%2Fnavigation-systems%2Faustralias-differential-global-positioning-system&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADifferential+GPS" class="Z3988"></span></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAustralia2024" class="citation web cs1">Australia, Geoscience (2024-04-24). <a rel="nofollow" class="external text" href="https://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-australia/about-the-program/southpan">"Southern Positioning Augmentation Network (SouthPAN)"</a>. <i>Geoscience Australia</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2024-09-07</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Geoscience+Australia&rft.atitle=Southern+Positioning+Augmentation+Network+%28SouthPAN%29&rft.date=2024-04-24&rft.aulast=Australia&rft.aufirst=Geoscience&rft_id=https%3A%2F%2Fwww.ga.gov.au%2Fscientific-topics%2Fpositioning-navigation%2Fpositioning-australia%2Fabout-the-program%2Fsouthpan&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADifferential+GPS" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Differential_GPS&action=edit&section=12" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output 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href="https://web.archive.org/web/20070711202730/http://www.tfhrc.gov/its/ndgps/02072.htm">US NDGPS fact sheet</a></li> <li><a rel="nofollow" class="external text" href="http://www.navcen.uscg.gov/?pageName=dgpsMain">USCG Navigation Center National DGPS system</a></li> <li><a rel="nofollow" class="external text" href="http://www.navcen.uscg.gov/?pageName=dgpsCoverage">USCG coverage maps</a></li> <li><a rel="nofollow" class="external text" href="http://www.ccg-gcc.gc.ca/eng/CCG/DGPS_Home">Canadian Coast Guard DGPS information (English)</a></li> <li><a rel="nofollow" class="external text" href="http://www.ccg-gcc.gc.ca/fra/GCC/DGPS_Accueil">Canadian Coast Guard DGPS information (French)</a></li> <li><a rel="nofollow" class="external text" href="http://www.hydro-international.com/productsurvey/id10-RTK_DGPS_Receivers.html">Product Survey on RTK DGPS receivers</a> for (mainly) hydrographic use</li> <li><a rel="nofollow" class="external text" href="http://www.coaa.co.uk/dscdecoder.htm">DGPS Decoding Software</a></li> <li><a rel="nofollow" class="external text" href="https://ndblist.info/datamodes.htm">Useful DGPS Links, Databases and Resources</a></li> <li><a rel="nofollow" class="external text" href="http://www.gnsspro.com/referencestations.php">Worldwide database of IALA DGPS Reference stations on an interactive map</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150717063508/http://www.gnsspro.com/referencestations.php">Archived</a> 2015-07-17 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline 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href="/wiki/DORIS_(satellite_system)" title="DORIS (satellite system)">DORIS</a></li> <li><a href="/wiki/Galileo_(satellite_navigation)" title="Galileo (satellite navigation)">Galileo</a></li> <li><a href="/wiki/GLONASS" title="GLONASS">GLONASS</a></li> <li><a href="/wiki/Global_Positioning_System" title="Global Positioning System">GPS / NavStar</a></li> <li><a href="/wiki/Indian_Regional_Navigation_Satellite_System" title="Indian Regional Navigation Satellite System">IRNSS / NAVIC</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Historical</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/BeiDou#BeiDou-1" title="BeiDou">BDS / BeiDou-1</a></li> <li><a href="/wiki/Transit_(satellite)" title="Transit (satellite)">Transit</a></li> <li><a href="/wiki/Timation" title="Timation">Timation</a></li> <li><a href="/wiki/Tsiklon_(satellite)" class="mw-redirect" title="Tsiklon (satellite)">Tsiklon</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/GNSS_augmentation" title="GNSS augmentation">GNSS augmentation</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/European_Geostationary_Navigation_Overlay_Service" title="European Geostationary Navigation Overlay Service">EGNOS</a></li> <li><a href="/wiki/GPS_Aided_GEO_Augmented_Navigation" class="mw-redirect" title="GPS Aided GEO Augmented Navigation">GAGAN</a></li> <li><a href="/wiki/GPS%C2%B7C" title="GPS·C">GPS·C</a> (retired)</li> <li><a href="/wiki/Joint_Precision_Approach_and_Landing_System" class="mw-redirect" title="Joint Precision Approach and Landing System">JPALS</a></li> <li><a href="/wiki/Local_Area_Augmentation_System" class="mw-redirect" title="Local Area Augmentation System">LAAS</a></li> <li><a href="/wiki/MTSAT_Satellite_Augmentation_System" title="MTSAT Satellite Augmentation System">MSAS</a></li> <li><a href="/wiki/Networked_Transport_of_RTCM_via_Internet_Protocol" title="Networked Transport of RTCM via Internet Protocol">NTRIP</a></li> <li><a href="/wiki/Quasi-Zenith_Satellite_System" title="Quasi-Zenith Satellite System">QZSS / Michibiki</a></li> <li><a href="/wiki/Southern_Positioning_Augmentation_Network" title="Southern Positioning Augmentation Network">SouthPAN</a></li> <li><a href="/wiki/StarFire_(navigation_system)" title="StarFire (navigation system)">StarFire</a></li> <li><a href="/wiki/Wide_Area_Augmentation_System" title="Wide Area Augmentation System">WAAS</a></li> <li><a href="/wiki/System_for_Differential_Corrections_and_Monitoring" title="System for Differential Corrections and Monitoring">SDCM</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related topics</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/GNSS_reflectometry" title="GNSS reflectometry">GNSS reflectometry</a></li> <li><a href="/wiki/Kalman_filter" title="Kalman filter">Kalman filter</a></li> <li><a href="/wiki/United_Kingdom_Global_Navigation_Satellite_System" title="United Kingdom Global Navigation Satellite System">United Kingdom Global Navigation Satellite System</a></li> <li><a href="/wiki/Wavelet" title="Wavelet">Wavelet</a></li> <li><a href="/wiki/RINEX" title="RINEX">RINEX</a></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" 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