Surely once traveling through some point in Spain you’ve seen a Plate hanging on the facade of a historic buildingCity Council or train station indicating the altitude of that place with respect to the sea level In the city of Alicante. Because Compare the altitude of a city like Pamplona or Soria with respect to the Levantine city is a question that has a scientific answer and that we are going to inevit today in Xataka.
The first thing to keep in mind is that sea level is not the same or constant by the different tides, Nor is it much less the same throughout the earth. That is why each country takes as Reference level a specific point of its territory. It is what is known as zero level. And any altitude that you want to calculate in that country will be made compared to that data.
Nor can we forget that The technology we have now compared to what existed two centuries ago it is not even for the same. Then there were no altimeters, which we now see anywhere: the car, the mobile, gas stations … that made calculating the altitudes of any place was a very laborious work that required an infinite patience.
The task of choosing that reference point also occurred in Spain. Specifically, he fell to the National Geographic Instituteinaugurated in 1856, which was entirely dedicated at that time to elaborate precise topographic maps of the country. In a publication of the institution in the 10th Hispanic-Portuguese Assembly of Geodesia and GeophysicsThey explain that Alicante’s choice was not a coincidence.
This article mentions that for the measurement to be as stable as possible, a low point had to be chosen so that negative heights were not produced, hence the sea level was chosen. So a site was sought on the Spanish coast in which The variations between low and pleamar were the minors possible. That is, I had to have Little maritime oscillation. That already completely ruled out some cities of the Cantabrian, because in places like Santander or San Sebastián the sea level can vary up to four meters during the day.
Four years of manual measurements
With that in mind, the scientists thought of the coast and the waters of the Mediterranean. Precisely Alicante, is inside a baywhere the daily variation of sea level is just a few centimeters. It was also found that this city was the best in terms of weather criteria, atmospheric pressure or seasonal variability.
But the most curious thing about the IGN’s decision was not the choice of the city, but the specific place where they decided to establish the zero level. To know exactly where to locate it, They made daily measurements from 1870 to 1874 by handhelping only a strip on the queen stairs located in front of the port of Alicante. After almost four years of work, it was decided to establish that right point on the first step of the interior stairs of the City of Alicante.
Specifically it was determined that this exact step It was 3.41 meters above sea. There a plaque was installed that says: “NP 1”. That is, precision level 1. since then, all the altimetry in Spain was measured according to the difference with this point, adding 3.41 meters. “From there, the altitudes were transferred to the rest of Spain through leveling lines and branches that would form the first high precision leveling network (Rednap),” Explain the institute In the report.
Obviously, over time and the continuous expansion of the port network in Spain, the Mareographers have changed site, other new ones being built to achieve a continuity of the data series.
In fact, today there are 10 operational stations throughout the country: Alicante 1, Alicante 2, Cartagena, Almería, La Coruña, Alborán (Isla de Alborán), Santa Cruz de Tenerife (Island of Tenerife), Puerto de la Cruz (Isla de Tenerife), Los Cristianos (Isla de Tenerife), Puerto del Rosario (Isla de Fuerteventura).
Image | Dean Milenkovic
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