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Sterrekunde is vir my nuut, so my vraag kan dom wees: ek lees dat 'n seemyl gedefinieer word as een minuut breedtegraad op enige lengtelyn. Sê nou dit was andersom, dws een minuut lengte oor enige breedtelyn? Sou dit enige verskil maak?
Ja, baie so.
Die lyne of sirkel met konstante lengtelyn vorm altyd 'n groot boog wat met die pole kruis; dus het dit altyd dieselfde lengte. 'N Sirkel met konstante breedtegraad wissel in omtrek: die grootste is aan die ewenaar, terwyl dit tussenlengtes op die breedte het en geen lengte meer het as u die pool bereik nie.
Kyk bv. die beeld vanaf die Wikipedia en volg 'n sirkel in lengte-lengte, dus van Noord na Suid. En vergelyk die verskillende groottes van verskillende sirkels vir verskillende breedtegrade (dus die sirkels wat parallel is aan die ewenaar)
Let egter daarop dat die seemyl nie meer deur die breuk van die poolomvang van die aarde gedefinieer word nie. Dit word gedefinieer as presies 1852m lank, en kan dus in beginsel so akkuraat bepaal word as wat mens tyd kan meet (1852/299 792 458 sekondes).
Vroeër was dit BAIE makliker om 'n breedteverskil te bepaal, aangesien dit direk verband hou met die hoogtepunt van hemelse voorwerpe bokant die horison. Dit was BAIE moeilik tot onmoontlik om die verskil in lengte-lengte te bepaal, tensy u 'n baie akkurate horlosie en 'n almanak van die opkoms en vasgestelde tye van hemelse voorwerpe gehad het.
Wat is die verskil tussen 'n seemyl en 'n wetlike myl? En wat is 'n knoop?
Volgens die Encyclopedia Britannica was 'n seemyl vroeër gebaseer op die kromming van die aarde en was dit ongeveer een minuut (boogsegment) breedtegraad langs 'n meridiaan (lengtelyn wat van noord na suid loop). Die Britse seemyl is op 6,080 voet gestel, terwyl die Amerikaanse seemyl op 6080,20 voet was. In 1929 is die seemyl egter herdefinieer tot presies 1,852 km (ongeveer 6076,11549 voet) tydens 'n internasionale konferensie wat in Monaco gehou is, hoewel die VSA eers in 1954 die omskakeling gemaak het.
1 seemyl = 1,1508 wetlike myl of 1,852 km.
'N Knoop (spoedmeting, nie die soort wat u in u skoenveters vasmaak nie) is gelyk aan een seemyl per uur.
1 knoop = 1,15 myl per uur.
Daar is basies twee verskillende kategorieë: seemeenhede en wetlike eenhede. 'N Paar keer vroeg in my lugvaartloopbaan het ek die twee gemeng (veral maklik as u in 'n vliegtuig vlieg wat mph gebruik, maar u seemyl op u snit meet) en dit sal onakkurate getalle lewer, wat redelik gevaarlik kan wees, afhangende van die berekening wat u doen. Dit is die drie hoof kinematiese eenhede wat verband hou met beweging van elke kategorie en waardes wat u vir omskakelings kan gebruik:
Kategorie: seevaart / statuut (omskakelingswaardes)
Afstand: seemyl / wetlike myl 1 / 1.15
Dit volg almal op die vergelyking afstand = spoed * tyd (solank u nie die kategorie meng en ooreenstem nie (nautiese eenhede met wetlike eenhede of andersom).
Histories gesproke is die seemeeue deur matrose gebruik omdat dit net praktieser was - een seemyl is oorspronklik gedefinieer as een minuut breedtegraad (breedtelyne is die wat die aarde horisontaal sny - dink 'platheid'), 'n afstand wat relatief konstant is (alhoewel dit nie heeltemal so is nie as gevolg van die aarde se ellipsoïede vorm, maar baie meer as minute lengte wat baie wissel). Dit was gemakliker vir matrose om te gebruik as wettige kilometers omdat breedtegraad (sowel as lengtegraad) gereeld gebruik is om posisie te definieer, sodat dit makliker was om te gebruik vir dooie afrekening en navigasie. Breedtegraadlyne een graad van mekaar is ongeveer 69 myl van mekaar af op die oppervlak van die aarde (wissel effens afhangend van u ligging op die oppervlak van die aarde), dus is een minuut breedtegraad (1/60ste van 'n breedtegraad) ongeveer 1,15 myl van mekaar af op die oppervlak van die aarde (69 myl / 60, want 'n minuut is 1/60ste graad). Aangesien 'n seemyl gedefinieer word as die afstand van 1 minuut breedtegraad, blyk dit dat 1 seemyl gelyk is aan 1,15 myl. Die werklike waarde word nou op ongeveer 1.15078 statutêre myl gestel omdat die seemyl herdefinieer is tot presies 1852 meter (nou internasionaal aanvaar). Etimologies is die term afgelei van matrose wat die aantal knope in die tou tel wat in 'n spesifieke tyd van die haspel van 'n spaanderstok (basies 'n touspoel) afgespoel is. Lugvaart volg baie vlootkonvensies, insluitend seemeenhede.
As u aan kilometers in die normale lewe dink (20 myl ry, myl hardloop, ens.), Is dit alles myle. Gewoonlik behoort die eenhede in die lugvaart sowel as in die vloottoepassings tot die kategorie seemanne (20 seemylvlug, 120 ktas (knope ware lugspoed)). Onlangs het sommige vliegtuigvervaardigers egter 'n beroep gedoen op die gebruik van wetlike eenhede in hul handleidings / lugvaartuie, hou dus die eenhede dop, veral op meer moderne vliegtuie. Wat die lugvaartstelsels betref (watter kategorie weerberigte gebruik en watter beheerders gebruik), is alles in die kategorie nautiese, behalwe om die sigbaarheid te meet (u sou windlesings op 10 knope van 160 grade hoor, byvoorbeeld 'n sigbaarheidsverslag van meer as 10 statute miles byvoorbeeld).
'N Soortgelyke belangrike onderskeid (nie verwant aan wetgewing nie) is dat wanneer u hoeke LEES (grade op 'n windvoorspelling of 'n METAR), die grade gewoonlik verwys na WARE noord (vir vlugbeplanningsdoeleindes). As u hoeke HOOR (ATIS-verslag, beheerder-windverslag), is die grade gewoonlik met verwysing na MAGNETIC noord. In elk geval terug na nautiese / statute.
As u vliegtuig wel wetteenhede gebruik, is daar heel waarskynlik 'n mylkant van u plotter (sodat u wettige kilometers op u deursnee sowel as seemyl kan meet) - gebruik dit in plaas van om die eenhede om te skakel, dit sal u tyd bespaar en foute. Die meeste luchtsnelheidsaanwysers kan ook knope en mph lees, alhoewel die buitekring die een is wat behoort tot die kategorie wat heel waarskynlik in die handleiding (in waardes vir vaarspoed, ens.) Heers - in hierdie geval mph.
Wat is 'n seemyl, en hoe verskil dit van 'n normale myl en 'n kilometer?
A seemyl is gebaseer op die omtrek van die planeet Aarde. As u die aarde by die ewenaar middeldeur sou sny, kan u een van die helftes optel en die ewenaar as 'n sirkel beskou. U kan die sirkel in 360 grade verdeel. U kan dan 'n graad in 60 minute verdeel. 'N Minuut boog op die planeet Aarde is 1 seemyl. Hierdie meeteenheid word deur alle lande vir lug- en seereise gebruik.
A knoop is 'n maateenheid vir spoed. As u met 'n snelheid van 1 seemyl per uur ry, word gesê dat u met 'n snelheid van 1 knoop ry.
'N Kilometer word ook gedefinieër deur die planeet Aarde as 'n afstandstandaard te gebruik. As u die aarde sou neem en dit in die helfte sou sny langs 'n lyn wat van die Noordpool deur Parys gaan, en dan die afstand van die kromme vanaf die Noordpool na die ewenaar in die sirkel meet, en dan die afstand met 10 000 deel , sou u die tradisionele eenheid vir die kilometer hê soos in 1791 deur die Franse Akademie vir Wetenskappe gedefinieer.
'N Watermyl is 1 852 meter, of 1,852 kilometer. In die Engelse meetstelsel is 'n seemyl 1,1508 myl, of 6.076 voet.
Om by die ewenaar om die aarde te reis, moet u (360 * 60) 21 600 seemyl, 24 857 myl of 40 003 kilometer reis.
Ook genoem Internasionale seemyl, dit is 'n meeteenheid wat gelykstaande is aan 1,852 kilometer of 6076 voet. Dit het die Britse seemyl van 6080 voet en die Amerikaanse seemyl van 6080.20 vervang deur 'n internasionale ooreenkoms wat in 1929 in Monaco gehou is.
Volgens die US National Institute of Standards and Technology (NIST) is die internasionale seemyl van 1852 meter (6076.115 49 & # 8230feet) effektief op 1 Julie 1954 vir gebruik in die Verenigde State aangeneem. Die waarde wat vroeër in die Verenigde State gebruik is, was 6080,20 voet = 1 seemyl (geografies of op see). ”
Seemyl is gebaseer op die omtrek van die aarde en word gebruik vir see- of lugreise. Gestel jy sny die aarde in die helfte by die ewenaar, kies die helfte daarvan en kyk deur as 'n sirkel. U verdeel dan die sirkel in 360 grade en verdeel 'n graad verder in sestig minute. 'N Minuut van 'n boog van die aarde is gelyk aan een seemyl. Dit beteken dat as u by die ewenaar om die aarde beweeg, u 'n totaal van 21.600 seemyl (360 x 60) sal aflê.
'N Knoop
Die term knoop dateer uit die 17de eeu toe antieke seevaarders die snelheid van hul skip gemeet het met 'n toestel genaamd 'common log' of 'chip log'. Met hierdie metode is knope met eenvormige tussenposes in 'n tou vasgemaak wat aan die einde 'n stuk snyvormige hout gehad het. Die hout is toe agter die skip geslinger. Terwyl die vaartuig beweeg, het die tou vir 'n spesifieke tyd vry uitgerol en daarna is die aantal knope getel en gebruik om die snelheid van die vaartuig te bereken. Die spoed is na bewering die getelde aantal knope.
Na die standaardisering van seemyl in 1929 is ooreengekom dat die knoop sy standaardeenheid van metingsnelheid is, bereken op grond van tyd en afstand.
Op datum word knope gebruik in navigasie en lugvaart, wat normaalweg op die lugspoedaanwysers van vliegtuie getoon word en word uitgedruk in terme van seemyl per uur. As u byvoorbeeld met 'n snelheid van 1 seemyl per uur beweeg, sê ons dat u teen 'n snelheid van 1 knoop beweeg.
Die myl
Die konsep van myl ontstaan uit die antieke Romeinse tyd. Die Romeine het vroeër mylpale op hul paaie geplaas, wat hulle gebruik het om afstand te meet met behulp van 'n eenheid genaamd mille passum, 'n Latynse woord wat duisend tree beteken. Daar word geskat dat elke pas vyf Romeinse voete is, wat beteken dat duisend tree gelyk is aan 5.000 Romeinse voet, ongeveer 4.850 van die moderne voete.
Rondom die jaar 1500 in Londen is myl gedefinieer as agt lengtes. 'N Furlong is 'n ou Engelse lengte-eenheid gelykstaande aan 625 voet. Gedurende die regeringstydperk van koningin Elizabeth I is 280 voet bygevoeg aan die 5 000 voet oorspronklike myl, onder 'n statuut van 1593 wat die lengte van 'n lengte tot 660 voet verhoog het, vandaar die huidige 5280 voet per wetlike myl.
Omskakeling van knope in kilometer per uur
Spoed in kilometer per uur is die afstand in kilometers afgelê in presies 3,600 sekondes. As een kilometer binne een uur afgelê word, druk ons dit as 1 km / uur uit.
Verskeie berekeningsinstrumente is geskep om die omskakelingswerk in verskillende eenhede te vergemaklik.
Die onderstaande tabel vir die omskakeling van windspoed maak dit byvoorbeeld makliker om knope in myl of seemyl per uur om te skakel en andersom.
1 knoop = 1 seemyl per uur
1 seemyl = 6076,12 voet = 1852 m
1 Statuut myl = 1760 meter = 5280 voet
Waarom Nautical Mile langer is as Mile
Seemyl word gemeet aan die hand van die aarde se omtrek en is gelykstaande aan een minuut breedtegraad.
A myl is gebaseer op landmeting wat geneig is om korter as die omtrek te wees. Die verskil word bewerkstellig deur die feit dat die aarde nie 'n perfekte sfeer is nie, maar geneig is om aan die pole plat te word.
Om die wet om te skakel na seemyl, gebruik ons faktor 1.15, alhoewel dit nie akkurate resultate lewer nie.
Byvoorbeeld
'N Wettige myl = 5,280 voet
Dit beteken dat die resultaat 4 voet skaam is van die werklike syfer van 6.076 voet seemyl.
Voorafgestelde tafels en omsetters soos Bowditch & # 8217s Table 20 kan gebruik word om meer presiese resultate te gee.
Seekaarte
Aangesien seemyl langs lengtelyne volg, is dit baie handig om te navigeer. Matrose en vlieëniers het intussen vorendag gekom seeskaarte wat dien as grafiese voorstelling van die aarde en fokus op die watergebiede.
Hierdie grafiek gebruik een van die drie kaartprojeksies: polikonic, gnomyc en Mercator. Nautiese kaarte vergemaklik die navigasie in oop waters, wat dit 'n baie belangrike instrument in die skeepvaart en verkenning maak.
Dit kan in gedrukte of elektroniese navigasievorm wees. Tegnologiese vooruitgang het papiergrafieke maklik beskikbaar gestel en kan op aanvraag gedruk word. Dit het die werk van matrose en seevaarders vergemaklik omdat hulle op die hoogte sal wees van die akkuraatste inligting wat nodig is vir hul reis.
Afsluiting
Beide wetlike en seemyl is eenhede van afstand, maar word afgelei en anders gebruik.
A myl is 'n lengte-eenheid op land wat gelyk is aan 5,280 voet en is deel van die Verenigde State se standaard-eenhede. In vergelyking met die metrieke stelsel is 'n kilometer ongeveer 1 609 meter en dit word afgekort as m
A seemyl is afstandseenheid wat gebruik word vir beide see- en lugreise en is gelyk aan 1,852 meter. Dit is gebaseer op 'n minuut boog op die aardbol, met 3600 sekondes boog per lengte-lengte. Dit word afgekort as nm.
Wanneer u geografiese kaarte gebruik, moet u seker wees van die afstandmeting wat gebruik word. Dit is omdat verskillende kaarte verskillende metings gebruik. Vier maatstawwe wat algemeen op kaarte gebruik word, sluit in:
& # 68 & # 101 & # 102 & # 105 & # 110 & # 105 & # 116 & # 105 & # 111 & # 110 & # 115 & # 32 & # 102 & # 111 & # 114 seemyl noukeurige myl
'N Lengte-eenheid wat ongeveer een minuut breedteboog langs enige meridiaan ooreenstem. Volgens internasionale ooreenkoms is dit presies 1,852 meter (ongeveer 6,076 voet).
Freebase (0.00 / 0 stemme) Beoordeel hierdie definisie:
Die seemyl is 'n lengte-eenheid wat ongeveer een minuut breedteboog gemeet word langs enige meridiaan, of ongeveer een minuut lengteboog by die ewenaar. Volgens internasionale ooreenkoms is dit presies 1,852 meter bepaal. Dit is 'n nie-SI-eenheid wat veral deur navigators in die skeepvaart- en lugvaartbedryf gebruik word, en ook in die polêre verkenning. Dit word algemeen in internasionale reg en verdrae gebruik, veral met betrekking tot die perke van territoriale waters. Dit het ontwikkel vanaf die seemyl en die verwante geografiese myl. Die seemyl bly wêreldwyd in gebruik deur see- en lugnavigateurs vanweë die gemak daarvan wanneer daar met kaarte gewerk word. Die meeste seekaarte gebruik die Mercator-projeksie waarvan die skaal met ongeveer 'n faktor van ses van die ewenaar tot die 80 ° breedte wissel, dus kaarte wat groot gebiede dek, kan nie een lineêre skaal gebruik nie. Die seemyl is byna gelyk aan 'n minuut breedtegraad op 'n kaart, dus kan 'n afstand wat met 'n kaartverdeler gemeet word, ongeveer in seemyl omgeskakel word met behulp van die breedtegraadskaal van die kaart.
Watermyl vs Miles
In 1929 het die internasionale seemyl is omskryf deur die eerste internasionale buitengewone hidrografiese konferensie in Monaco as 1 852 meter.
Imperiale eenhede en gebruiklike eenhede van die Verenigde State het 'n definisie van die seemyl gebaseer op die Clarke (1866) Spheroid. Die watermyl van die Verenigde State is gedefinieer as 6.085,20 voet (1,853,24 m) gebaseer in die Mendenhall Order-voet van 1893. Dit is in 1954 verlaat ten gunste van die internasionale seemyl.
Die Keiserlike seemyl, wat dikwels 'n Admiraliteitsmyl genoem word, of meer korrek, 'n Admiraliteitsgemete myl, soos gedefinieër deur sy verhouding tot die Admiraliteitsknoop & # 8211 6.080 keiserlike voet per uur & # 8211, dus 1 keiserlike seemyl is ongeveer 1,853,181 meter. Dit is in 1970 laat vaar en, wetlik, word verwysings na die verouderde eenheid nou omgeskakel na 1 853 meter.
As u nog onseker is oor die verskil tussen seemyl en myl, kom aan boord van Yacht La Pinta, en dit sal alles dadelik duidelik wees. Stel jou voor die oop oseaan voor jou, wonderlike wild wat vrylik om jou rondloop, en jou bekommernisse ver agter. Elke konsep, eenvoudig of ingewikkeld, het skielik 'n nuwe betekenis en die seemyl wat u deur die Galapagos-eilande sal reis, sal gevul word met die wonderlikste herinneringe.
Nautiese sterrekunde
'n tak van praktiese sterrekunde wat beantwoord aan die behoeftes van navigasie. Nautiese sterrekunde is gemoeid met die ontwikkeling van metodes om vanaf hemelliggame en navigasie-, kunsmatige aardsatelliete die posisie van 'n skip op see te bepaal en regstellings vir kursusaanwysingsinstrumente. Nautiese sterrekunde is deel van die wetenskap van navigasie.
Die posisie van 'n skip op see, dit wil sê sy geografiese breedte & # 981 en lengte en lambda, word bepaal deur die hoogtes van hemelliggame oor die sigbare seehorison of oor die vlak van 'n kunsmatige horison wat op verskillende maniere op die skip geskep word, te meet. . Die gebruik van hoekmeetapparate met 'n kunsmatige horison het die moontlikhede vir skeepsposisies op astronomiese wyse uitgebrei en ook die akkuraatheid in die meet van hoogtes van hemelliggame verhoog.
Elke waarde h van die ware hoogte van 'n hemelliggaam lewer een vergelyking op vir die bepaling van die skip- & rsquos-koördinate, sodat ten minste twee metings van die hoogtes van hemelliggame benodig word om 'n skeeps- & rsquos-posisie op see te bepaal. Die oplossing van die sferiese driehoek met hoekpunte aan die hemelpool, die hoogtepunt van die waarnemer, en die posisie van die ster & mdash, dit is die parallaktiese of astronomiese driehoek & mdashleads na die vergelyking
waar & oslash en tGr is onderskeidelik die deklinasie en die Greenwich-uurhoek van die hemelliggaam. Die waardes van & delta en tGr word gekies uit 'n mariene astronomiese almanak vir die oomblikke van waarneming. Die lengte- en lambda word ooswaarts vanaf die Greenwich-meridiaan gemeet: tGr + & lambda = tlok is die plaaslike uurhoek van die hemelliggaam. Wanneer die hemelliggaam op die meridiaan van die waarnemer in die hoogste hoogtepunt is (tlok = 0), vergelyking (1) lewer die oplossing & # 981 = & delta & plusmn (90 & deg - H), waar H is die hoogte van die hemelliggaam in die boonste hoogtepunt, die meridiaanhoogte genoem. Die minusteken word geneem vir die deurvoer van die hemelliggaam noordwaarts vanaf die hoogtepunt.
As vergelyking (1) opgelos word t ioc, dan kry ons die vergelyking
(2) cos tlok = sonde n . sek & oslash. sek & delta - tan & oslash. bruin & delta
As ons die breedtegraad & # 981 van die posisie ken, kan ons ook die lengte- & lambda = verkry tlok & mdash tGr gebruik vergelyking (2).
Dit is moontlik om die lengte- en breedtegraad van 'n posisie uit twee hoogtemate te bepaal. Met 'n groter aantal metings kan die akkuraatheid van die bepaling ook geëvalueer word. Deur die geskatte posisie van die skip te gebruik, dit wil sê die koördinate (& # 981e, & lambdae) van die posisie wat grafies of analities aangetref word met betrekking tot die koershoek en afstand wat afgelê word (doodrekening), kan ons elkeen van die vergelykings wat in die vorm van 'n foutvergelyking verkry word, voorstel of elke vergelyking geometries interpreteer as 'n hoogteposisielyn. Die posisie-lynvergelyking het die vorm
Om die posisielyn te konstrueer, word die geskatte posisie van die skip (& # 981e, & lambdae) is die oorsprong van koördinate (sien Figuur 1), met die breedtegraadinkomst & Delta & # 981 wat op een as geteken is en die ooreenstemmende afstandsinkrement & DeltaW = & Delta & lambda. cos & # 981 langs die ander as. As die verskil & Delta h = h & mdash he tussen die hoogte van die hemelliggaam wat deur waarneming gevind is, en die geskatte hoogte bereken vanaf die geskatte koördinate word geteken vanaf die geskatte posisie in die rigting wat deur die azimut bepaal word A van die hemelliggaam, dan 'n punt K word gevind, die onderskep genoem. Die posisielyn gaan deur die afsnit in die rigting loodreg op die azimut van die hemelliggaam.
Die skeepsposisie word bepaal deur die snypunt van die posisioneringslyne van twee sterre wat voortdurend waarneembaar is. Vir 'n groot aantal waarnemings sny die posisionele reëls in die reël nie op een punt nie, maar vorm 'n foutfiguur. Die mees waarskynlike posisie van die skip kan gevind word deur middel van 'n grafiese metode of analities.
Die regstelling vir kursusaanwysers word bepaal deur die waargenome dra van 'n hemelliggaam en die azimut te vergelyk A van hierdie liggaam, bereken vanaf sy bekende deklinasiehoek van 8 uur tlok = tGr + & lambda, en die breedtegraad van die waarnemingsposisie. Die azimut A kan uit die vergelyking bereken word
(4) bedjie A = cos & oslash. bruin & delta. cos tlok - sonde & oslash. bedjie tlok
Wanneer die hoogte van 'n hemelliggaam gelyktydig met die dra van die liggaam gemeet word, kan die azimut bereken word deur een van die vergelykings te gebruik.
(5) sonde A = cos & delta. sonde tlok. sek h
(6) cos A = sek & oslash. sonde & delta. sek h - bruin en oslash. Tan h
Spesiale tabelle vir die berekening van die azimut van 'n hemelliggaam is gepubliseer.
Die hoogte van 'n hemelliggaam oor die sigbare seehorison word met 'n sekstant gemeet.
Om die hoogte te bepaal h van 'n hemelliggaam oor die regte horison word die lesing wat op die skaal van die sekstant verkry is, gekorrigeer deur die instrumentele regstelling van die sekstant, 'n indeksekorreksie en korreksies wat die onderdompeling van die sigbare horison, breking en die helfte in ag neem. -diameter en die parallaks van die hemelliggaam.
Historiese opname. Die posisies van hemelliggame is al in die afgeleë Oudheid gebruik vir oriëntering op 'n onbekende posisie en vir die bepaling van die rigting van die reis. Die groei van nywerheid en handel en die uitbreiding van die navigasie wat met hierdie groei gepaard gaan, het gelei tot die begin van die 15de eeu in die ontwikkeling van metodes en instrumente vir die bepaling van 'n posisie op die oop see. Astronomiese instrumente wat geskik is vir die waarneming van sterre aan boord, insluitend hoekstawe, weerkaatsende kwadrante, sterrebane en armillêre sfere, het wydverspreid geword. Efemere van die son en planete, wat nodig is om waarnemings uit te voer, is bereken. Op hierdie tydstip kon slegs die breedtegraad van 'n posisie uit astronomiese waarnemings bepaal word. In die 16de en 17de eeu is metodes voorgestel om lengtegraad te bepaal op grond van waarnemings van die hoekafstande tussen die maan en sterre en waarnemings van die verduisterings van Jupiter & rsquos-satelliete. 'N Presiese metode om die lengte van 'n posisie te bepaal, gebaseer op die berekening van die verskil tussen die plaaslike uurhoek van 'n hemelliggaam en die waarde daarvan op die oomblik van waarneming vir die Greenwich-meridiaan (& lambda = tlok & mdash tGr) is eers in die tweede helfte van die 18de eeu in die astronomie bekendgestel, met die konstruksie van die chronometer.
'N Teorie vir die gesamentlike bepaling van breedte- en lengtegraad is in die vroeë 19de eeu ontwikkel. In 1808 het die Duitse wiskundige K. Gauss 'n metode voorgestel wat die oplossing van vyf vergelykings vereis. In 1824 publiseer die Russiese geodesis F. F. Shubert 'n nuwe metode vir die gesamentlike bepaling van & # 981 en & lambda. Hierdie metodes blyk egter ongeskik te wees vir praktiese toepassing. In 1843 publiseer die Amerikaanse seeman T. Sumner 'n metode vir die bepaling van 'n skeepsposisie gebaseer op die feit dat die posisiesirkel wat ooreenstem met die waarde van 'n gemete hoogte, dit wil sê die sirkel van gelyke hoogtes, oor 'n kort afstand voorgestel kan word deur 'n reguit lyn op 'n kaart. Hy het hoogteposisie-lyne gekonstrueer deur middel van die punte waarop hierdie lyne twee parallelle lyne sny naby die breedte-parallel van die geskatte posisie. Die Russiese seeman A. A. Akimov het 'n ander metode voorgestel, wat in 1849 gepubliseer is, vir die konstruksie van die posisionele lyn met behulp van die enkele snypunt van die posisielyn met die geskatte breedtegraad parallel en die rigting van die posisie lyn. Die loodregtheid van die hoogteposisielyn en die rigting na die ster is die eerste keer in hierdie metode gebruik. In 1875 het die Franse seeman M. Saint-Hilaire 'n metode voorgestel om die hoogteposisie deur 'n spesifieke punt en loodreg op die rigting na die ster te trek. Hierdie metode word steeds in die 20ste eeu gebruik. Die Sowjet-wetenskaplikes N. N. Matusevich en V. V. Kavraiskii het baie bygedra tot die ontwikkeling van moderne metodes van nautiese sterrekunde en die stelselmatige toepassing van die algemene metode van posisioneringslyne vir die oplossing van astronomiese probleme.
Met behulp van seemyl
Vandag is een seemyl nog presies gelyk aan die internasionaal ooreengekome maatstaf van 1,852 meter (6,076 voet). Een van die belangrikste begrippe om die seemyl te verstaan, is die verhouding tot breedtegraad. Omdat 'n seemyl gebaseer is op die aarde se omtrek, is 'n maklike manier om die berekening van 'n seemyl te verstaan, om jou voor te stel dat die aarde in die helfte gesny word. Sodra dit gesny is, kan die sirkel van die helfte in gelyke gedeeltes van 360 ° verdeel word. Hierdie grade kan dan in 60 minute verdeel word. Een van hierdie minute (of minute boog soos dit in navigasie genoem word) langs 'n groot sirkel op aarde verteenwoordig een seemyl.
In terme van wetlike of landmyl, verteenwoordig 'n seemyl 1,15 myl. Dit is omdat een breedtegraad ongeveer 69 myl lank is. 1/60 van die maatreël sou 1,15 myl wees. 'N Ander voorbeeld is om die aarde rond te ry by die ewenaar om dit te doen.' N Mens moet 40.003 km ry. As dit omgeskakel word na seemyl, sal die afstand 21 600 NM wees.
Benewens die gebruik daarvan vir navigasiedoeleindes, is seemyl ook steeds beduidende snelheidsmarkers, aangesien die term "knoop" vandag een seemyl per uur beteken. Daarom, as 'n skip teen 10 knope beweeg, beweeg dit teen 10 seemyl per uur. Die term knoop soos dit vandag gebruik word, is afgelei van die voorgaande gebruik om 'n stomp ('n geknoopte tou aan 'n skip vasgemaak) te gebruik om die snelheid van 'n skip te meet. Om dit te doen, sou die stomp in die water gegooi word en agter die skip getrek word. Die aantal knope wat gedurende 'n sekere tyd van die skip af en in die water oorgegaan het, sou getel word en die getal sou die snelheid in 'knope' bepaal. Die hedendaagse knoopmetings word bepaal met meer tegnologies gevorderde metodes, soos meganiese sleep, Doppler-radar en / of GPS.
Definisie van 'n seemyl - Sterrekunde
The Nautical Mile in Freeport is een van my gunsteling plekke om 'n middag op die water te geniet. 'N Vreemde kombinasie van restaurante en werkbote, kroeë in die buitelug en vismarkte, lewendige musiek en mishorings. Dit is 'n mengsel van nautiese sjarme en straatfeeste wat ek moeilik kan weerstaan.
Oor die Naam
Toe ek 'n kind was en voordat ek ooit hierheen gekom het, het ek die naam gestomp. Ek kon net nie die dubbele betekenis verstaan nie en het heeltyd gewonder waarom iemand 'n kilometer wil gaan sien. Ek kry dit nou, maar net vir ingeval jy dit nie doen nie
The Nautical Mile is die nie-amptelike bynaam vir Woodcleftlaan, die pad wat langs die Woodcleftkanaal in Freeport loop.
Ongeveer 'n kilometer lank en aan albei kante gevoer met allerhande maritieme chaos, word dit The Nautical Mile genoem vanweë die lengte daarvan (moet niemand vertel nie, maar dit is regtig ongeveer 25% kort) en sy karakter.
Die voorkoms en die gevoel
As u nog nie 'n rukkie hier was nie, kan u dalk 'n verrassing hê.
Danksy die suksesvolle herlewingspoging deur die dorp Freeport, is die huidige Nautical Mile ver van die ou tyd af.
U onthou dalk oorstroomde strate en stukkende sypaadjies. Nou sal u 'n pragtige baksteen-esplanade, parkbanke, planters, 'n fontein en aantreklike buitemuseum-uitstallings vind.
Alhoewel die Nautical Mile nou meer besoekersvriendelik is, het dit nie in 'n toeristeval verander nie.
Dit is immers die tuiste van die huur- en kommersiële vissersvloot van Freeport, en dit is die middelpunt van een van Long Island se oudste maritieme gemeenskappe.
Agter die kosmetiese opgraderings is waar die vissermanne werk. Met ander woorde, dit ruik nog steeds na vis - op 'n goeie manier natuurlik.
Dinge om te doen
Die Nautical Mile leef met die toerisme-aantreklikhede, geluide en reuke van die see. Soos die buurtpark, is dit nie soseer 'n plek om te vermaak nie, maar 'n plek om jouself te vermaak.
Loop die Esplanade
Op 'n sonnige dag kan u ure deur die esplanade loop (wel, ek kan dit in elk geval).
Ek hou daarvan om alles in te neem, en ek kyk ook baie na mense. My eerste stop van die dag is altyd een van die eetplekke in die buitelug.
Ek sal 'n plek vind wat nie te druk is nie, maag tot by die kroeg en 'n drankie drink. Bier, Coke, wat ook al, en as dit rondom etenstyd is, het ek dalk 'n ligte versnapering. Al die tyd geniet ek die bootverkeer op en af in die kanaal.
Daar speel gewoonlik 'n band en as hulle goed is, hou ek vas totdat hulle 'n blaaskans neem. Dan gaan dit na die volgende plek en die volgende band.
Restaurante
Aandete is altyd op my Nautical Mile to do-lysie. Daar is geen tekort aan restaurante hier nie, en hulle bedien meer as net vis - u kan kry waarvoor u lus is, en dan 'n paar.
Hier is 'n paar aanbevelings, maar verken dit in elk geval. Daar is byna 2 dosyn restaurante op die Nautical Mile met elkeen sy eie persoonlikheid:
Bracco & # 8217s Clam and Oyster Bar
Bracco & # 8217's is baie gemaklik en het nogal 'n groot eetarea buite.
As u vars vis wil hê, is dit die plek, want dit kom direk vanaf hul eie bote by Cap & # 8217; t Ben & # 8217 s Fish Dock reg langsaan.
Daar is niks fynproewers aan Bracco nie, net goeie vars kos gebak, gestoom of gebraai.
Otto & # 8217s se Sea Grill
Man, dit is DIE kuierplek. Fietsry, maar vriendelik, bied Otto & # 8217s binne en buite etes en ordentlike kos.
Die buitelugarea het twee kroeë en 'n baie klein verhoog vir die groep. Daar is selfs 'n dansvloer.
As u op soek is na 'n naglewe, probeer dit vir Otto.
E.B. Elliot & # 8217s
Dit is die nuutste en mees luukse restaurant op die Nautical Mile-eetplek.
Spyskaartaanbiedinge wissel van hamburgers en patat tot bekroonde biefstuk, stadig geroosterde prima rib en geskroeide geelvintuna.
U kan u maaltyd geniet vanaf 'n tweede verdiepingbalkon met 'n duidelike uitsig reg langs die kanaal of die groot eetarea buite. E. B. Elliot & # 8217s is 'n deftige plek en natuurlik nie goedkoop nie.
Bracco & # 8217's is baie gemaklik en het nogal 'n groot eetarea buite.
Man, dit is DIE kuierplek. Fietsry, maar vriendelik, bied Otto & # 8217s binne en buite etes en ordentlike kos.
Dit is die nuutste en mees luukse restaurant op die Nautical Mile-eetplek.Roomys en miniatuurgholf
Het jy kinders? Wil u hulle miskien na die Crow & # 8217s Nest Miniature-gholfbaan neem of na een van die yswinkels neem vir 'n bietjie roomys (hulle kan nie kla oor al die tyd wat u in die geskenkwinkel spandeer nie) Hulle mond is vol).
Probeer: Ralph se Italiaanse ys of Pip's Roomys.
Jachthavens
Mans kan na bote kyk op maniere wat vroue jaloers maak.
Met nawe, jachthavens en boothandelaars (oke, seiljagmakelaars) is die Nautical Mile langs die kanaal die perfekte plek om te fantaseer oor die boot wat u eendag kan besit.
Sommige jachthavens is toegemaak, dus wees versigtig dat jy nie toegesluit word nie. Ja, dit het met my gebeur. Gelukkig daag daar na 'n kort tydjie 'n boteienaar met 'n sleutel op en laat ons uit.
Vismarkte
Vir sommige mense is die vismarkte net lelike, stinkende plekke, maar vir my is dit die hemel op aarde.
Ek hou daarvan om na al die verskillende vis wat op die ys versprei is, te kyk. Ek hou van die nat vloere, die reuk, die kreeftenks en die bossies vol blou kloukrappe. Daar moet iets in my bloed wees.
As u van vars vis hou, is dit die plek om dit te koop.
There are three fish markets on the Nautical Mile offering everything from catfish to snappers, bluefish and tuna, clams, cockles, crabs, lobster and oysters, mussels, squid and octopus, scallops, conch, steamers and flounders.
The list is almost endless. It’s off the boat fresh and it’s all delicious.
Live Music
Most of the eateries on the Nautical Mile have live music. It’s not hard to find, just keep your ears open and go with what you like.
More than the food it’s usually the music that draws me in to a particular place.
One Sunday afternoon while my girlfriend and I were enjoying a beer at Otto’s, I found myself standing in the way of a band ( Strung Out ) setting up their equipment.
Suzin, the band’s manager, simply informed me that since I was standing in her dancing spot, I’d have to do the dancing instead. That was the start of a snappy banter (Suzin is quite the spitfire) that went on all night long.
And, we got to meet a celebrity.
Rocco Abbondola (a.k.a. Rocky The Dancer) showed up!
Left: Rocky and Suzin take a break between sets.
What? You’ve never heard of him?
That’s okay, neither did we, but he's someone we’ll never forget.
Gift Shops
No seaside attraction would be complete without gift shops. You know, the kind where you can buy a starfish or a kite or a painting by a local artist? The Nautical Mile has a few, but my favorite is Frank's Art Shack.
The place is packed so full of stuff it's hard to walk, the prices seem reasonable and there are a lot of nice photographs and artwork for sale.
Cruises & Charter Fishing Boats
Several cruise boats and a fish load of charter and party boats hail from the Nautical Mile and Guy Lombardo Boulevard on the opposite side of Woodcleft Canal.
There are too many boats to list here, but you can go for a dinner or casino cruise or even have your wedding afloat. And, you can charter a boat for any kind of fishing you like.
Of course, for things like this it’s best to make reservations ahead of time.
Lodging
If you’re visiting Long Island and want to stay near the Nautical Mile there are two hotels in Freeport to choose from:
Freeport Motor Inn & Boatel (516-623-9100)
Yankee Clipper Motor Inn (516- 379-2005)
Getting Here & Parking
Getting to the Nautical Mile is not as hard as these directions make it seem. The route is clearly marked and all you really have to do is follow everyone else once you get off the parkway.
- Meadowbrook Parkway south to Merrick Road west.
- Left on Mill Road.
- Left on Henry Street (South Main Street)
- Right on Atlantic Avenue.
- Left on Guy Lombardo Boulevard
- Right on Front Street.
- Left on Woodcleft Avenue.
Once you get here start looking for a parking space. If you don't see any or don't like parking on the street, look for the municipal parking lot on your right about halfway down.
If there's nothing available there, you can park legally on the side street west of Woodcleft Avenue. Just drive through the parking lot and you'll see it.
Talk:Nautical mile/Archive 1
According to WP:UNITS, the preferred wikipedia abbreviation for nautical mile is nmi. This is to avoid confusion with nanometer, although one would think the context would be enough. I think this probably should be in the article, but am putting it here, as someone questioning it is likely to ask here. I only hesitate to put it in the article as it seems like wikipedia self references are to be avoided in mainspace. --J Clear (talk) 17:59, 2 February 2008 (UTC)
Having spent several years in the Navy, I have made some adjustments based on the following:
Nautical Miles for navigation are measured at exactly 6,000 feet (2,000 yards). A cable is 1/10 of a mile, or 200 yards. A cable also happens to be exactly 100 fathoms. While this measurement differs slightly (about 76 feet per mile) from the internaitonal standard, it is used by most navy and merchant vessels because of the much simpler mathematics involved.Mattwilkins 16:15, 18 October 2005 (UTC)
I cannot add clarification to this or a reference. I can agree with below - exactly 2000 yards to is a close approximation, simplify math. However I believe No mariners of any country use meters & kilometers at sea. Matt Wilkens defines cable and fathom as sub-units of nautical mile, I do not think that is the orginal definition of those units, instead I suspect original cable and fathom definition was perhaps as 6 feet = 1 fathom, 1 cable = 100 fathoms. Amongst mariners the 6000 feet = 1 nmi is accepted. 74.214.43.199 (talk) 01:41, 21 October 2010 (UTC) Can you add a good authoritative a reference for this? A link to some online Navy standards handbook, for example? In which country's Navy was that? Is this really an official definition, or just a crude approximation for rule-of-thumb calculations in countries that still use feet and yards? Markus Kuhn 20:28, 19 October 2005 (UTC) The Canadian Navy. The Bride Watchkeeper's Exam uses 2000 yards to the Nautical Mile. Mattwilkins 08:11, 15 November 2005 (UTC) Simpler only if you're using feet, fathoms and cables. Don't you mean "most U.S. navy and merchant vessels"? Jimp 2Nov05 Well all vessels use these measurements, as the metric system is very difficult to use to any effect. How exactly is the logical and coherent International System of Units (SI) "very difficult" to use on the sea? Or the air for that matter? Samy23 22:11, 14 January 2007 (UTC) I take it you are not a navigator. When you are working with nautical charts, it is usually easier to measure a distance using the latitude markings on either edge of the chart than to find the scale, which is frequently folded out of sight, especially on smaller craft. Also you are frequently dealing with converting degrees/minutes/seconds to distances, where the nautical mile is equivalent to 1 minute of arc (of latitude). For similar reasons, the knot is still used as the unit of velocity in the sea or air. In a way the nautical mile is similar to the hectare, both have a niche use where they are more efficient to use than SI units. --J Clear (talk) 17:49, 2 February 2008 (UTC) This is a weird sentence "Also in maritime navigation, nautical miles can be divided into 10 cables, although the present day definition of the cable uses a much more precise method.". "A tenth of a nautical mile" is perfectly precise, especially if nautical miles are defined with respect to meters which are defined with respect to the speed of light. —Preceding unsigned comment added by Schmmd (talk • contribs) One tenth nautical mile was a stadion of 185m. The Greeks measured 8 stadions (cables) to a thousand of land (mia chilioi) and 10 stadions to a nautical mile. The Romans measured 75 mille passus or milliare to a degree. 12.187.95.196 (talk) 10:30, 19 September 2013 (UTC)
"It bulges at the equator like a spinning top," says the article. Do spinning tops bulge at the equator? Jimp 2Nov05
They would. If they were made up of a sufficiently plastic material.--zumanon 14:13, 25 January 2007 (UTC)
In an edit summary, Ericg said "rv - if you think about it, bulging at the equator means the north-south distance is korter at the equator, not longer."
The problem is, his thought experiment would lead to the opposite conclusion when it is farther away, the same angle subtends a greater distance.
The problem is, we don't normally measure geocentric latitude, so we don't have our angles located at the same origin. Instead, we normally use geodetic latitude see the article, it's too complicated to summarize here. If we used geocentric latitude, a minute of arc would be greater at the equator than at the poles.
But with the geocentric latitude we do use, a minute of arc is greater at the poles than at the equator. The numbers aren't exactly the same, however, and I haven't checked yet to see which kind of latitude the numbers used in the article correspond to. There are also a few other ways that could possibly be used to measure latitude (which is what you measure as you travel along a meridian of longitude). Gene Nygaard 00:17, 13 December 2005 (UTC)
Geodesy#Units and measures on the ellipsoid states: "A nautical mile is one minute of astronomical latitude. The radius of curvature of the ellipsoid varies with latitude, being the longest at the pole and shortest at the equator as is the nautical mile". So the statement of Nautical_mile#History: "According to WGS84 the length of one minute of arc along a meridian on the Earth's surface varies from 1852.2 m near the poles to 1855.3 m near the Equator." cannot be true. Nor does the article WGS84 support it. Bo Jacoby 13:14, 21 July 2006 (UTC)
The length of a Sea Mile is the shortest at the Equator (1842.9m) and the longest at the Poles (1861.7m). An average value of 1852.3m is at 45 degrees Latitude. (IYT YM Ocean handbook). A cable, being a tenth of a mile, equals 185.2m or ROUGHLY 200 yards. — Preceding unsigned comment added by Bingbongbelgium (talk • contribs) 20:12, 12 March 2007
Seeing that the sea mile is 6000 feet exactly, it can hardly vary from place to place. It must be the metre (an other geographic unit, equal to 0.1 centisimal second), that varies. A nautical mile represents a degree at the surface of a sphere approximating the earth. Wendy.krieger (talk) 07:50, 3 June 2012 (UTC)
It sounds like the sea mile is defined in different ways by different organisations (a really good reason not to use this unit). The article should start by pointing out the ambiguity, and then provide the various conflicting definitions. Dondervogel 2 (talk) 10:35, 3 June 2012 (UTC) A meter is a unit of length that does not vary anywhere on Earth's geoid. If it was oriented along the equator it would subtend 2.16 milliseconds of time. If it was oriented parallel to any other line of latitude (all small circles), it would subtend greater periods of time at greater latitudes. At 89° it would subtend about 124 ms. A nautical mile is one arcminute (not one degree) of any great circle on the surface of the Earth, including along the equator and along any meridian/antimeridian, but not along any parallel of latitude other than the equator. Using this definition it varies no more than 0.5% from 1852 meters, the International nautical mile. The "sea mile" definition of 6000 feet is due to Richard Norwood in his extraordinarily popular Seaman's Practice (1637) which was still being sold in 1776, and quoted as an authority in 1822. He personally observed the altitude of the Sun in London at the summer solstice of 1633 and in York at the summer solstice of 1635, and measured the meridional distance between them using chains and pacing. He then calculated that a degree of latitude was 367,196 English feet, but rounded this to 360,000 feet per degree or 6000 feet per arcminute. All commentators until the mid 19th century noted that 6000 feet was a rounded value. — Joe Kress (talk) 05:54, 4 June 2012 (UTC) Joe Kress says: "A nautical mile is one arcminute (not one degree) of any great circle on the surface of the Earth, including along the equator and along any meridian/antimeridian, but not along any parallel of latitude other than the equator." That's not correct. As the article makes clear, a nautical mile is not one minute of any arc, but is defined internationally as 1852 meters exactly. By the way, Richard Norwood's A Seaman's Practice is still in print today, available from Amazon. Dondervogel 2 says: "It sounds like the sea mile is defined in different ways by different organisations (a really good reason not to use this unit). The article should start by pointing out the ambiguity, and then provide the various conflicting definitions." The article is about the modern term "nautical mile", not about the disused term "sea mile", so it correctly starts out by defining the former. The latter is taken up in the second section, where it is clear that there are at least three definitions of "sea mile", two of them official, and one of which has changed since 1966. . . Jim - Jameslwoodward (talk to me • contribs) 10:53, 4 June 2012 (UTC) Jim completely ignored my statement "Using this definition it varies no more than 0.5% from 1852 meters, the International nautical mile." so I was obviously refering to the nautical mile's historical definition, which is correct. Most of my definition even appears in the lead paragraph, prefixed with "about" to account for the difference I explicitly mentioned. The article is not only about the modern term nautical mile, it is about all historical definitions as well. I see two print versions of Richard Norwood's Seaman's Practice available, from BiblioBazar and Eebo editions. Both appear to be printed versions of microfilm/microfiche editions published during the last half of the 20th century. As such they contain all defects of the microfilm/microfiche editions, including off center and cropped pages and illegible letters, words, paragraphs or pages. The second, Eebo editons, is obviously a copy of the copy in Early English Books Online viewable at many libraries (one page at a time). — Joe Kress (talk) 01:45, 5 June 2012 (UTC) We're quibbling over a very small point, and since I started it, I'll take the blame. The problem here is that many readers do not understand this subject very well -- read all of this talk page, including the claim below that a nautical mile is a minute of longitude, not latitude, and you will see what I mean. Therefore, I react when someone makes a statement that may mislead other readers -- it is absolutely correct that a nautical mile is very close to a minute of any great circle -- that is, after all, the whole point of using the special unit for navigation -- and I did note your comment that it varied by less than half a percent, but you must agree that your flat statement, without qualifiers, is not correct. As for the Norwood, certainly it's a copy of a microfilm, but it interested me that it was readily available, in stock at Amazon. Of course old sea books have long lives -- Bowditch has been continuously in print for more than 200 years. Of course, unlike Norwood, Bowditch has been revised more or less continuously over its entire life. . . Jim - Jameslwoodward (talk to me • contribs) 23:08, 5 June 2012 (UTC) Early English Books Online is the online version of four microfilm collections issued between 1938 and the present. One collection is Early English Books by Donald Wing, which contains Mr. Richard Norwood's Works, which contains the 1670 ninth edition of Seamans Practice. Although the online version has a few duplicate pages, and many pages that tilt toward each other, none of this affects its legibility. I did not consult either printed version. After observing the altitude of the Sun from both York and London and measuring the length between them in chains, Norwood concluded on page 5 that one degree of a great circle was 367196 English feet or 367200 feet "lacking 4 feet, which here we regard not." Norwood stated that the latter made a degree 69 English miles 4 furlongs 14 poles [69.54375 statute miles, where 8 furlongs/mile × 40 poles/furlong × 16.5 feet/pole = 5280 feet, which conflicts with 367200 feet / 5280 feet/mile = 69.54545 miles. Norwood mentioned "and about one half [of a pole]" earlier, but not here. He should have specified an additional 9 feet beyond 14 poles for 367200 feet (he mentioned 5 feet earlier for 367196 feet)]. On page 48 he assigned to a degree only 360000 feet so a mile was 6000 English feet. This was intentionally shorter than the length of the degree that Norwood measured so that reckoning by a log line with knots would indicate that the ship had sailed its intended distance before it reached its intended destination to avoid surprise, and "for the rotundity of the number". Norwood never used the terms "sea mile", "geographical mile", or "nautical mile". He only used "mile" for each of the 60 miles in a degree. — Joe Kress (talk) 05:10, 23 June 2012 (UTC)
In the discussion on the Knot (speed) page, someone says regarding the metric conversion to km: "1.852 is a round up (the actual precise number being 1.851999985024)" Anyone? Fizzybrain 12:38, 17 April 2006 (UTC)
I just looked at the BIPM reference. It says 1852 not 1852.5 meters. Has our definition really been wrong all along? I just corrected it. 16:09, 13 December 2006 (UTC)
I modified the conversion section to indicate which conversions have exact (rational) values, and also grouped the two approximate values together at the end. Lacking any more precise definition of geographical mile than one arc minute at the Earth's equator, this can only be as exact as the current estimate of the latter, and likewise for the arc minute itself, which certainly is not exactly one nautical mile given the SI standardization to 1852 m. --Vaughan Pratt 01:02, 15 August 2007 (UTC)
In one section ( toward the bottom ) the Wiki page lists a nautical mile as exactly 1,852 meters. In another section, we're told "The Imperial (UK) nautical mile, also known as the Admiralty mile, was defined in terms of the knot such that one nautical mile was exactly 6080 feet (1853.184 m):[5] it was abandoned in 1970[5] and, for legal purposes, is now converted to metres on the basis of one UK nautical mile = 1853 metres exactly.[6]" —Preceding unsigned comment added by 70.91.201.209 (talk) 23:26, 15 January 2010 (UTC)
Both are correct. The international nautical mile is exactly 1,852 m. The Imperial nautical mile was defined as 6080 feet, which is equivalent to 1853.184 m. However, when the UK decided to abandon the Imperial nautical mile, they also decided that if old references to it need to be converted to SI, the old references should be converted with a conversion factor of 1853 meters to the Imperial nautical mile. --Jc3s5h (talk) 23:50, 15 January 2010 (UTC)
This entry never explains what SI is -- perhaps whoever added it could include it? It's not very clear to me what SI is from the context.
International System of Units, now Wikilinked in the second sentence. Atlant 16:58, 5 June 2006 (UTC)
In the article box where it has conversions is states 1 nautical mile = 1088.259 miles, which can't possibly be right. However, I know nothing about nautical stuff so is there something I'm missing here? --Cammy 19:15, 11 August 2006 (UTC)
Somebody has screwed up the < "The term 'knot' derived from the practice of using a knotted rope as a method of gauging speed of a ship. The rope would be thrown into the water and the rope trailed behind the ship. The number of knots that passed off the ship and into the water in a given time would determine the speed in 'knots'." This really sounds like nonsense folk etymology. I'd always had the impression 'knot' was simply a respelling of 'nauts', short for 'nautical miles (per hour)'. This thing about dropping knots sounds like nonsense. 192.128.167.68 11:00, 25 August 2006 (UTC) Nope, that's the exact etymology. So many knots on so many seconds. Atlant 18:20, 27 August 2006 (UTC) It's correct. The only early way to know a ship's speed was to use what is called a log line. Check dictionary definition 10b. ericg ✈ 19:01, 27 August 2006 (UTC) Sorry, I've never included a cite before. If someone else doesn't mind doing it this is an excellent explanation of the nautical term "knot." It even explains that "naut" as in nautical and "knot" as in a marker in a rope is purely coincidental. The use of a wooden wedge is explained, to serve as a sea anchor, thus insuring that the rope would play out properly, along with a 30 second "hourglass", and a length of knotted (not nauted) rope. The process involved three persons. The timekeepr, the knot counter, and the rope player-outer. This link http://www.tallshipbounty.org/Demos_ChipLog.html includes photos and further explaination of the "chip log." It all started with logs being thrown overboard over the bow of a ship on a mark and someone counting the seconds that passed until the log passed the stern. The vessel's size was known and this way the speed could be calculated and entered in the LOG-book. Later they tied a rope to the log so they could re-use the same log over and over again and thus saving valuable storage space. Eventually they ended up with the knotted rope. The articles states that 1 nautical mile is equal to 1.1507794 geographical mile. Yet, the geographical mile article states that geographical mile is 1855 meters, which means that 1 nautical mile is equal to 1852/1855 = 0.9984 geographical mile. Hence, (at least) one of the two statements has to be wrong, though I do not know which one. Changed, I assume that one nautical mile is equal to 0,9984 geographical mile (according to the [Geographical mile] definition). Tatrgel 13:52, 14 January 2007 (UTC) The quick-and-dirty approximation used for practical navigation is that a nautical mile is 15% longer than a statute mile: 5280 ft X 1.15 = 6072 ft ≈ 6,076.1 This is also known as "slide rule accuracy" — the kind of precision one would get with a traditional E6B Flight Computer. —Quicksilver T @ 19:11, 8 January 2009 (UTC) I have almost by chance noticed that the radius at the poles were shown to be greater than the radius at the equator, which is of course wrong it is a known fact that the earth is bulging at the equator. Also the corresponding lengths of one minute of arc was wrong. So I consulted the WGS 84 for the radii and made the necessary calculations of the arc myself. --zumanon 14:05, 25 January 2007 (UTC) Actually I have seen the same error in various websites from which I suppose the main body of the article has been copied. If I have time I will revisit this article and check other figures at least for conceptual errors.--zumanon 14:10, 25 January 2007 (UTC) No error, the radius of kromming of a meridian attains its minimum at the equator and maximum at the poles. You are probably thinking of another radius, namely the distance from the surface to the center of the earth, which as you say is the other way round. Take a look at the geodetic constants in http://www.jqjacobs.net/astro/xls/aegeo.xls. The relevant ones here are sma (semimajor axis or equatorial radius), smi (semiminor axis or polar radius), fr (flattening reciprocal, = smi/sma), and rcp (radius of curvature, polar), all IUGG values (for consistency). Missing is rce (radius of curvature, equatorial). You can get all of these from just sma (6378137 exactly) and fr (0.996647189318820) alone, using smi = sma×fr, rcp = sma/fr, and rce = sma×fr 2 . So smi and rcp go in opposite directions from sma, while rce/rcp, the ratio of the two curvatures, is fr 3 = .989975, i.e. the radius of curvature decreases by 1.0025 per cent going from pole to equator. Memorizing this as one percent is all the accuracy you'll ever need in practice (oblateness works in mysterious ways). --Vaughan Pratt 22:33, 16 August 2007 (UTC) Right now the content related to the various articles relating to measurement seems to be rather indifferently handled. This is not good, because at least 45 or so are of a great deal of importance to Wikipedia, and are even regarded as Vital articles. On that basis, I am proposing a new project at Wikipedia:WikiProject Council/Proposals#Measurement to work with these articles, and the others that relate to the concepts of measurement. Any and all input in the proposed project, including indications of willingness to contribute to its work, would be greatly appreciated. Thank you for your attention. John Carter 20:56, 2 May 2007 (UTC) Anonymous editor 74.161.41.234 keeps changing the definition to: Unit of distance used in navigation, an internationally agreed standard (since 1959) equaling the average length of one minute of arc on a great circle of the Earth, or 1,852 m/6,076 ft. Refer to: http://geodesy.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf However, the cited reference does not mention "one minute of arc" and it gives a much more precise length than 6,076 ft. The first is already mentioned in the 'definition' as an approximation and the second is given almost as precisely as that in his ref in a list below the definition (Conversions to other units). — Joe Kress 22:45, 27 August 2007 (UTC) The anonymous editor is also wrong that it became an international standard in 1959. Various sites, including the BIH site, state that it was internationally accepted in 1928. 1959 is the much later year that the United States accepted it. I left a note on his talk page (User talk:74.161.41.234) requesting him to respond here. Because all of his edits have used the same numeric IP address, he should see an alert that he has a message on any Wikipedia page. — Joe Kress 23:50, 28 August 2007 (UTC) There should be a short and absolute definition in the beginning of the main article text of that what a nautical mile equals to meters. This is the main inadequacy of the article.It must be clearly expressed that a nautical mile e quals to 1852 m. at the very begining. because many people may want to obtain shortly the meter equivalent of nmi.so i am writing down this knowledge at the main definition paragraph .yes it is existing in the frame but it must also be in text either. —Preceding unsigned comment added by 85.108.76.2 (talk) 03:02, 12 February 2010 (UTC) I reformatted the reference in the lead sentence to point directly to Table 8 in the BIPM brochure, rather than a section that contains several tables. I also removed some unsourced remarks from the footnote. In particular, the footnote contained the quotation "expected to continue to be used for many years", but that phrase does not occur anywhere in the BIPM brochure (unless there is some quirk that prevents the search facility in Adobe Acrobat Reader from finding it). --Gerry Ashton 18:01, 30 August 2007 (UTC) Sorry for the misquote. The phrase is actually, "continue to be used for many years", which occurs in the first paragraph of section 4.1: "Tables 8 and 9 contain units that have exactly defined values in terms of SI units, and are used in particular circumstances to satisfy the needs of commercial, legal, or specialized scientific interests. It is likely that these units will continue to be used for many years." This quote is also the source for the excised statement that it is "an exact SI definition". I've not been able to confirm the original statement that "At one time, the nautical mile was discouraged for use by the BIPM" due to a lack of access to early editions of the SI brochure. The 7th edition notes that in 1969 the CIPM "listed three categories of non-SI units: units to be maintained to be tolerated temporarily and to be avoided", but fails to state which category contained the nautical mile. An early table containing the nautical mile from an unknown edition was entitled "other units outside the SI that are currently accepted for use with the SI, subject to further review". The table in the 6th edition (1991) is entitled "units temporarily accepted for use with the SI" while the table in the 7th edition (1998) is entitled "other non-SI units currently accepted for use with the International System" (but its "use is not encouraged"), compared to the 8th edition (2006), which only has "other non-SI units". Although section 4.1 is entitled "non-SI units accepted for use with the SI, and units based on fundamental constants", even the preface to table 7 states that its units "are not generally used with SI". — Joe Kress 05:56, 1 September 2007 (UTC) If you have a view on what abbreviation(s) should or should not be used, you may be interested in reading this discussion. Thunderbird2 20:55, 4 September 2007 (UTC) As it stands now the lead mentions the abbreviations M, NM and nmi, and the Unit Symbol section mentions M and nm. I think the Unit Symbol section should mention NM and nmi as well. The discussion mentioned above has been archived. Ulflund (talk) 11:47, 8 December 2011 (UTC) In the history section, the fourth paragraph begins: "Other nations had different definitions of the nautical mile." I infer from this phrase that the preceding three paragraphs have been refering to one or more specific nations, yet none is mentioned. --Jamestowell 19:27, 9 September 2007 (UTC) You're right. It doesn't make sense. Feel free to improve the wording yourself when you spot something like this. Thunderbird2 19:49, 9 September 2007 (UTC) I have simplified the passage that explains the length of a minute of latitude. Since nautical miles are ordinarily used in navigation, it is appropriate to round to the nearest meter. Also, since nautical charts use geodetic latitude rather than geocentric latitude, I removed the passage about geocentric latitude. Also, I added a reference to the Explanatory supplement to the Astronomical almanac. --Gerry Ashton (talk) 19:59, 6 February 2008 (UTC) When was it adopted? Septentrionalis PMAnderson 16:09, 3 March 2008 (UTC) N.A.M. Rodgers, in The Wooden World: An Anatomy of the Georgian Navy, makes the following statement, "Commodore Frankland. reported dangerous variations in marking the log line, and consequently in reckoning distance run: 'The Winchester, by allowing only forty-two feet to a glass of thirty seconds, overrun her reckoning by near a hundred leagues between Madeira and this island [Barbados]. 35 He asked for an Admiralty order fixing the length of the log line. Endnote 35, Public Records Office, Letters of the Admiralty, T. Frankland, 18 Nov 1755. Now the above is far from a statement that in 1755, as a consequence of variations in marking the log line, the Admiralty fixed the nautical mile. However, as this period saw an increased cognizance in the import of precise and reliable navigation, I believe we are getting close, if you will. Would anyone care to opine? --Crusher1 (talk) 03:33, 20 April 2008 (UTC) The knot article defines a knot as one nautical mile per hour. The nautical mile definition says a nautical mile is defined as one knot divided by one hour. Somewhere there has to be an original definition for the (admiralty) nautical mile, but what was it? Rhialto (talk) 08:56, 7 March 2011 (UTC) The article title is "Nautical Mile so", and the page for "Nautical Mile" redirects here, but nowhere in the article is the "so" part defined. What does it mean? 150.101.166.15 (talk) 23:41, 27 March 2008 (UTC) The page has been vandalised, but I don't know how to fix it. The "so" is someone's idea of a joke. Does anyone know how to retrieve the correct name please? Thunderbird2 (talk) 10:14, 28 March 2008 (UTC) I have reported this vandalism WP:AIV. I hope an administrator will know the best method to undo this problem. --Gerry Ashton (talk) 14:20, 28 March 2008 (UTC) User:Skomorokh has fixed the problem. --Gerry Ashton (talk) 14:50, 28 March 2008 (UTC) Thanks. Thunderbird2 (talk) 15:36, 28 March 2008 (UTC) The Admiralty Manual of Navigation and the RYA Navigation Handbook both make a helpful distinction between these two terms. A Sea mile is the length of one minute of arc, along a meridian. It is actually calculated as the angle between two intersecting normals, it does not make reference to the centre of the earth. A "normal" is a line at right angles to a tangent and running through the tangent at the point it touches the curve. Since the earth is not a sphere, and its cross section not a circle, then the length of a Sea Mile does alter according the latitude it is taken. When a navigator takes a distance measure from the vertical edge of a chart, he is measuring sea miles. Nautical Miles are an attempt to create a "standard" or average Sea Mile, one which is the same no matter the latitude it is used. This is vital for specifying speeds, unless a knot is to have a slightly differing value at different latitudes. This is largely a matter of agreement between various maritime authorities. To sum up, this excellent article would be improved still further if the diagram were to be changed to say "sea miles", and distinction between the two be made more clearly. The variation of the length of a degree of latitude (60 minutes) relative to an ellipsoid is discussed at Latitude#Degree length. — Joe Kress (talk) 02:46, 12 April 2008 (UTC) Good point. That's something I noticed a while ago, then completely forgot to do anything about. When I find my copy of the Mariner's Handbook, I'll have a go at properly defining sea miles. There will probably have to be a mention made on Mile as well, and a redirect page created for Sea mile. Wardog (talk) 15:34, 18 June 2008 (UTC) I find the definition of sea mile in this article confusing. When I went to the source (The Admiralty Manual of Navigation) I was not confused. I made an ill-advised edit, which I have now reverted. It's the apparent (but not actual) redundancy of "1' of arc of latitude . along the current meridian" that throws me off track. OK. This is looking more and more like a problem with the way my brain is wired, and less and less like a problem with the writing. But for me, I think I could understand it better if the first bit just said 1' of arc along the current meridian at the current latitude. Then a second sentence could state this corresponds to 1' of latitude and briefly explain why 1' of latitude varies as a function of current latitude. In the source, when it was separated out, I found it easier to follow. Does anyone object to my trying to do a small rewrite in the next few days? Susfele (talk) 17:06, 20 June 2010 (UTC) Thank you, Jameslwoodward, for rewriting the sea mile definition. It's both more succinct and more understandable. Susfele (talk) 00:31, 22 June 2010 (UTC) The Mariner's Handbook defines the International Nautical mile as 1852m and the Sea mile as "the length of one minute of arc measured along the meridian in the latitude of the position its length varies both with the latitude and with the dimensions of the spheroid in use". It defines the geographical mile as "the length of one minute of arc measured along the equator its value is determined by the dimensions of the spheroid in use". The Admiralty Manual of Navigation Vol 1 (1987) says that the abbreviation for a nautical mile is "n.mile". It gives the abbreviation for sea mile as "M" on charts and '(as used for minutes of arc) elsewhere. Tim Bartlett —Preceding unsigned comment added by 82.153.197.217 (talk) 12:50, 2 January 2009 (UTC) I'm surprised to see 'radar mile' here. I think it is in the verkeerde artikel. The point is, a radar mile is measurement of tyd, nie a measurement of distance. As stated it is the time it takes for a radar (RF) signal to go a mile, strike an object and be reflected back to its origin. A radar mile is therefore 12.36 micro-seconds. It's a bit like calling 100 'sprint' metres, 20 seconds. (the time to run 100M and run back again) I'm being picky but it there is no other connections this could be deleted This information only belongs in the Radar article (or maybe in the Mile article —Preceding unsigned comment added by 220.101.28.25 (talk) 01:01, 25 October 2009 (UTC) The radar mile is a unit of time that it takes radar to travel one mile. This is the time it takes radio waves to go out and back, one mile. It is a unit of time, but as 'knot' is here as a derived unit (nm/hr), so should this unit (nm/radar). --Wendy.krieger (talk) 07:10, 30 August 2010 (UTC) It states "The nautical mile (symbol M, NM, Nm or nmi) is a unit of length corresponding approximately to one minute of arc of 'latitude' along any meridian. By international agreement it is exactly 1,852 metres (approximately 6,076 feet).” However, it is not latitude, but lengtegraad that one measures a nautical mile from (on a chart), as the length (or distance apart) of the minutes of latitude vary depending on how far from the equator one gets, whereas minutes of longitude do not. Hence, a nautical mile measured from a line of latitude near the Pole would give you a much shorter nautical mile than if measured along a line of latitude at the equator. However this variation does not occur in the lines of longitude and hence why longitude is ALWAYS used to measure a nautical mile. So that first line, and any others of similar nature referring to ‘latitude’ as the measure of a nautical mile in the article needs to be changed. — Preceding unsigned comment added by 124.150.97.91 (talk • contribs) 23:31, 15 February 2011 Nautical Mile: If a nautical mile is greater at the poles than at the equator, how can the earth be considered an oblate spheroid rather than a prolate spheroid? How can it be said that we know the earth is wider at the equator than at the poles given the length of a nautical mile is longer at the poles than at the equator?Goodhayman (talk) 12:33, 14 April 2011 (UTC) A frequent source of confusion. What you need to do is think about what latitude is. Suppose the Earth were much more oblate-- still an elliptical cross-section, but pancake-shaped. Where would 45 degrees latitude be? Near the equator, or near the poles? Tim Zukas (talk) 16:26, 21 October 2011 (UTC) Also the elliptic shape of Earth is a few meters of difference, or so - crossing waves at the oceans or sailing where the tides are strong means more. Not to speak of mountains on land. Boeing720 (talk) 02:53, 16 January 2015 (UTC) Unless there is an objection, I am going to remove this section. I can't find any substantive reference for a "telegraph mile" or "telegraphic mile" except a few sites on Google that provide conversions into or out of it. They may simply be built off of the definition here. It is certainly of less importance than many other uses of "mile" that we do not include here. . . Jim - Jameslwoodward (talk to me • contribs) 13:01, 17 February 2012 (UTC) There being no objection after waiting 2+ weeks, I have removed this section. . . Jim - Jameslwoodward (talk to me • contribs) 14:24, 7 March 2012 (UTC) From a mathematical point of view are the zeros incorrect. They suggest an accuracy of six digits. But the true value (modern definition) is 1,852 meter exactly. It's an integer value, not a floating one or "with decimals". There is no call for adding the zeros. Actually 1,852.00 means a value somewhere between 1,851.995 and 1,852.004. On the other hand in order to point out this is a four digit integer, it's expressed 1.853 x 10 3 , but that is an exaggeration. But not the added zeros. And I'm not a mathematican, just someone that has studied mathematics to a cetrain level (some lower university courses) a long time ago. Boeing720 (talk) 02:45, 16 January 2015 (UTC) A: Read this and draw your own conclusions. Dondervogel 2 (talk) 09:22, 28 December 2015 (UTC) That page simply shows the futility of trying to explain earth-centric nautical miles in SI metric or imperial units! For example, is a nautical mile on the moon equal to 1852m? Santamoly (talk) 09:31, 4 March 2016 (UTC) One nautical mile is equal to 1852 m, by definition. It doesn't matter whether you are on Earth, Mars or Alpha Centauri. But that's not what this thread was about. Dondervogel 2 (talk) 17:05, 4 March 2016 (UTC)
--158.38.82.84 12:50, 12 January 2007 (UTC)Circular Definition
