Our house is a shade over 600 metres above sea level. If you say that in feet it’s just shy of 2,000 feet which, in the UK, would be hilly. The Yorkshire Three Peaks Challenge with Pen-y-Ghent at 694 metres, Whernside at 736 metres and Ingleborough at 723 metres are all a bit lower than the humble, but 800 metre high hill, Xirivell, at the back of our house. Just a little further away the Sierra del Carche range, which you can see from Pinoso and which you drive alongside on the way to nearby Jumilla, rises to 1371 metres which is just a few metres up on Ben Nevis at 1345 metres. That said the Grampians, the Lake District or the Machynlleth Hills call for high tech footwear, cuben fibre gear and trekking poles while Xirivell is much more a flip flops and shorts hill. The difference is the height of the surrounding flatland.
The Spanish Ordnance Survey, the National Geographic Institute (IGN from it’s initials in Spanish), began work on the first topographic maps in 1857. One of the essentials for making maps which show heights, the topography, is to have reference points. The most basic of these is a base level and it’s sea level that is used. The trouble is that the sea level, for all sorts of reasons, varies from place to place on the various seas and oceans. The IGN decided that it would use Alicante as the place to measure sea level to give the basis for heights in Spain. They chose Alicante because it was quite easy to measure sea level there using basic instrumentation. The Mediterranean is relatively calm, the tidal variation is limited and it’s a comfortable place to be based. Cádiz or Santander might have been just as comfortable but the Atlantic has much bigger tidal variations and more frequent and violent storms.
So, between 1870 and 1872 the IGN measured the sea level just by where, nowadays, there is a statue which is called El regreso de Ícaro con su ala de surf – it’s the one that I always thought was a surfer until I wrote this piece. Apparently it’s a homage to those who try to dream and soar. The IGN used a metal ruler fastened to the wall with divisions every 5 mm and they measured the sea level every three hours between 9 in the morning and six in the evening for a couple of years. The mean variation was 0.43 metres. That gave them their sea level, the mean sea level, Point Zero or Cota cero in Spanish. I’m told there is a metal plaque on the seawall to mark the spot though I’ve never noticed it myself.
Now the IGN had its baseline they needed a spot on dry land to measure from. They chose the first step of the main staircase in Alicante Town Hall. Heaven knows why. The Town Hall is just 230 metres in a straight line from Point Zero and that first staircase step is 3.4095 metres above mean sea level. This measuring point was given the name NP1. It’s still the point from which the height of anywhere in Peninsular Spain is measured. If you’re ever in Alicante it’s easy to have a look. Anyone can walk in the front door of the Town Hall. The staircase is obvious enough, though you may notice that funny golden Dalí statue before it. You probably won’t notice the rather unimpressive bronze plaque, which is NP1, without looking for it. Then again the standard inch, foot, yard etc in Trafalgar Square aren’t exactly overwhelming either.
Once the IGN had something to go on it developed the precision levelling network (Red Española de Nivelación de Alta Precisión) which wasn’t completed till 1924. By drawing 92 lines between various places running along more than 16,500 kms of railway lines and roads they were able to place over 18,000 signs which marked fixed heights. Nearly 2,200 of those marks were principal signs which were placed in public spaces like town halls and railways stations. You will see them from time to time as you wander around Spain. The one in the header photo is from Villena railway station.
It has to be said that in today’s world a metal ruler on a seawall isn’t as accurate as it gets. The real variations in sea level depend on lots of factors, like the curvature of the earth, the amount of ice held in the polar ice caps, the phases of the moon and the like. Nowadays there are various tide meters dotted around the Spanish coast and satellites also measure sea level – I presume though I don’t know – that the two can communicate with each other so that there is accurate information about actual and mean sea levels at any time. Nonetheless, as we look out from our garden to the Salinas de Sierra mountain chain opposite we can say that the Pico de la Capilla is at 1238 metres above sea level at Alicante and that’s close enough for us.
This piece was originally posted to Life in Culebron. If you would like to see more posts of a similar nature click on the link
Nyumba yetu iko umbali wa mita 600 juu ya usawa wa bahari. Kwa mfano, ikiwa unasema kwamba ni mita, ni chini ya mita 2,000, ambayo, nchini Uingereza, itakuwa ni milima. Yorkshire Three Peaks Challenge, pamoja na Pen-y-Ghent kwenye mita 694, Whernside kwenye mita 736 na Ingleborough kwenye mita 723, zote ni chini kidogo kuliko kilima cha Xirivell, kilichokuwa nyuma ya nyumba yetu. Sierra del Carche, ambayo unaweza kuona kutoka Pinoso na ambayo wewe kuendesha pamoja na njia ya Jumilla, huinuka hadi mita 1371 na ni mita chache tu juu ya Ben Nevis. Hizi ni pamoja na Grampians, Lake District, Machynlleth Hills, na Xirivell, ambapo kila mtu anajua jinsi ya kutembea. Tofauti ni urefu wa eneo tambarare linalozunguka. "Kama ""Utafiti wa Sanaa ya Uhispania,"" Taasisi ya Kitaifa ya Kijiografia (IGN) ilianza kazi kwenye ramani za kwanza za topografia mnamo 1857, na ilianza kazi mnamo 1857, wakati ilikuwa ikijulikana kama ""Utafiti wa Sanaa ya Uhispania.""" Moja ya mambo muhimu ya kutengeneza ramani zinazoonyesha urefu, topografia, ni kuwa na vituo vya kumbukumbu. Msingi zaidi ya haya ni ngazi ya msingi na ni ngazi ya bahari ambayo hutumiwa. Tatizo ni kwamba kiwango cha bahari, kwa sababu mbalimbali, hutofautiana kutoka mahali hadi mahali kwenye bahari na bahari mbalimbali. Mfumo wa IGN ulipendekeza kwamba Alicante iwe kituo cha kupima kiwango cha bahari na kuamua urefu wa bahari. Walichagua Alicante kwa sababu ilikuwa rahisi sana kupima kiwango cha bahari huko kwa kutumia vifaa vya msingi. Bahari ya Mediterania ni ya utulivu, tofauti ya mawimbi ni mdogo na ni mahali pazuri pa kuwa msingi. Cádiz na Santander ni maeneo ya bahari yenye msukosuko, lakini bahari ya Atlantiki ina msukosuko mkubwa zaidi na dhoruba nyingi zaidi. "Kama ilivyoelezwa hapo juu, IGN ilichunguza kiwango cha bahari katika miaka ya 1870 na 1872 na ilipata picha ya ""El regreso de Ícaro con su ala de surf"" (Return ya Icarus na Surf) ambayo ilikuwa na picha ya mvinyo wa bahari." Yaonekana ni heshima kwa wale ambao kujaribu ndoto na kuruka. Wanasayansi walitumia mhimili wa chuma uliounganishwa kwenye ukuta na kugawanyika kila baada ya milimita tano, na walipima kiwango cha bahari kila baada ya saa tatu kati ya saa tisa asubuhi na saa sita jioni kwa miaka miwili. Tofauti ya wastani ilikuwa mita 0.43. "Hiyo ni kwa sababu ya kiwango cha bahari cha kawaida, ""Cota Cero"" katika Kihispania." Nimeambiwa kuna bamba la chuma kwenye ukuta wa bahari ili kuashiria mahali hapo ingawa sijawahi kuliona mwenyewe. Kwa hiyo, IGN ilihitaji eneo la msingi la kupima. Walichagua hatua ya kwanza ya ngazi kuu katika Jumba la Halmashauri la Alicante. Mungu anajua ni kwa nini. Jumba la Halmashauri la Jiji la London liko mita 230 tu kwa mstari wa moja kwa moja kutoka Point Zero na hatua ya kwanza ya ngazi iko mita 3.409 juu ya wastani wa usawa wa bahari. Sehemu hii ya kupima ilipewa jina NP1. Bado ni uhakika kutoka ambayo urefu wa mahali popote katika Peninsular Hispania ni kipimo. Kama wewe ni milele katika Alicante ni rahisi kuwa na kuangalia. Mtu yeyote anaweza kutembea katika mlango wa mbele wa Jumba la Halmashauri. Ngazi ni dhahiri kutosha, ingawa unaweza kuona kwamba funny dhahabu Dalí sanamu kabla yake. Kwa mfano, unaweza kuona picha ya shaba ya NP1 ikiwa haijulikani. Kisha tena inchi ya kawaida, mguu, yadi nk katika Trafalgar Square si hasa kubwa ama. Mara baada ya IGN alikuwa na kitu cha kwenda juu ya maendeleo ya usahihi leveling mtandao (Red Española de Nivelación de Alta Precisión) ambayo haikuwa kukamilika mpaka 1924. Kwa kuchora mistari 92 kati ya maeneo mbalimbali, wakitembea kwa zaidi ya kilomita 16,500 za reli na barabara, waliweza kuweka ishara zaidi ya 18,000 ambazo zilionyesha urefu wa mahali fulani. Karibu alama 2,200 kati ya hizo zilikuwa ishara kuu zilizowekwa katika maeneo ya umma kama vile majumba ya manispaa na vituo vya reli. Utawaona mara kwa mara unapotembea-tembea huko Hispania. Picha iliyo kwenye kichwa ni ya kituo cha gari-moshi cha Villena. Ni lazima iseme kwamba katika ulimwengu wa leo mtawala wa chuma juu ya seawall si sahihi kama inavyopata. Mabadiliko ya kiwango cha bahari hutegemea mambo mengi kama vile umbo la dunia, kiasi cha barafu katika barafu za barafu, awamu za mwezi na kadhalika. """Sasa kuna mita mbalimbali za mawimbi zikiwa karibu na pwani ya Hispania na satelaiti pia hupima kiwango cha bahari, nafikiri ingawa sijui, kwamba hizo mbili zinaweza kuwasiliana kwa kila mmoja ili kuwe na habari sahihi kuhusu kiwango cha bahari halisi na cha wastani wakati wowote." Hata hivyo, kama sisi kuangalia nje kutoka bustani yetu kwa Salinas de Sierra mlolongo wa milima kinyume tunaweza kusema kwamba Pico de la Capilla ni katika mita 1238 juu ya usawa wa bahari katika Alicante na kwamba ni karibu kutosha kwa ajili yetu. Kipande hiki awali ilichapishwa kwa Maisha katika Culebron. Kama ungependa kuona posts zaidi ya asili sawa bonyeza kiungo