Height above sea level & hellip, This term is probably known to every student. We often see him in newspapers, on websites, in popular science magazines, as well as when watching documentaries.
Now let's try to give it a more precise definition.
Section 1. Altitude above sea level. general information
This term should be understood as an absolute height or absolute elevation, that is, such a coordinate in three-dimensional space that shows at what height in relation to sea level this or that object is.
Two other indicators of the geographic location of an item are longitude and latitude.
Take Moscow, for example. The height above sea level of this city is very different: the maximum is 255 m (not far from the Teply Stan metro station), and the minimum - 114.2 m - is located near the Besedin bridges, exactly where the Moscow River leaves the city.
In general, if we operate with purely physical measurements, then the height above sea level is nothing more than the vertical distance from, in fact, the very individual object to the average level of the sea surface, which should not be disturbed by either tides or waves.
This value can be both positive and negative. Well, everything is relatively simple here: what is above the sea acquires a plus sign, and below it, respectively, a minus sign.
By the way, it should be noted that with an increase in its value, a decrease in atmospheric pressure is observed.
If we talk about our country, the 5642-meter Elbrus is rightfully considered the highest point of land in the Russian Federation, but the Caspian Sea with an absolute height of about 28 m can be called the lowest.
Section 2. Altitude above sea level. Highest place on the planet
Well, of course, this is Everest - a well-known mountain located in the central part of the Himalayan mountain range, right on the border of two South Asian states, Nepal and Tibet.
Today its height is 8848 meters. The words, for today, are not accidental. According to scientists, the earth's surface is still continuing to form, so this peak, although imperceptible, is growing every year.
If you delve into history, then almost immediately you can find information that the first brave conquerors of the Chomolungma were Edmund Hillary (New Zealand) and Tenzing Norgay (Nepal). They made their actually heroic ascent on May 28, 1953. Since then, Everest has become a kind of Mecca for hundreds and thousands of rock climbers, mountaineers and other daring adventure seekers.
Section 3. Altitude above sea level. The lowest place on the planet
In this case, things are a little more complicated. The fact is that there are two such points on Earth at once: one of them - the coast of the Dead Sea - is located on land, and the second is called the Mariana Trench and is located deep under the water column of the Pacific Ocean.
Let's dwell on each of them in more detail.
So, the Dead Sea, as you know, can be found on the border of three countries: Israel, Palestine and Jordan. It is not only the saltiest body of water on the planet, but the lowest land area.
Now the water level in it is 427 meters, but this is not the limit, because, according to experts, it falls by an average of 1 meter annually.
Altitude & hellip, Moscow, as mentioned above, ranges from 114 to 255 m. For us, this is, in principle, the norm. Considering that the capital of the Russian Federation can hardly be called very hilly, this difference is almost impossible to feel.
And now let's pick up a globe or a physical map of the earth's surface: somewhere deep, deep in the Pacific Ocean, not far from the Guam Islands, you can see a mark with the inscription Mariana Trench. So, it goes under water to a depth of just over 11 km.
We all studied geography at school and are familiar with the term "height above sea level" firsthand. This definition can be found in popular science television programs, on the pages of magazines, newspapers and other media. Let's take a look at modern ways of defining it.
The sea level, relative to which the distance to the object is measured, is a water surface at rest, located perpendicular to the resultant forces applied to the body of water. The water level changes very often and this is due to the phases of the moon, the strength of the sun and wind, evaporation. Therefore, to calculate the average, it takes years to carry out the necessary calculations.
Altitude is a point (coordinate) in a three-dimensional area that indicates how high a particular object is in relation to zero sea level. It can also be roughly defined as the vertical from the object to the average height above sea level, without taking into account the ebb and flow. The height of a point located above the level is considered positive, below it is considered negative. The other two coordinates for the geographic location of the object are longitude and latitude.
If we take Russia as an example, then its highest point is Elbrus - 5642 meters, and the lowest is the Caspian Sea, the highest point of which is about 28 m.
How to find out the altitude above sea level
In the old fashioned way, the height above sea level can be viewed in special topographic maps, in which all heights are displayed. But there are more modern methods.
- You can find out what altitude above sea level using a satellite navigator powered by a specific program, for example, Google or Google Earth (Google Earth). First, you need to download one of the applications to your smartphone or computer and, using the prompts, determine the distance from sea level to the object you need. Working with the programs is very simple: hover the cursor over the desired place on the map, and the information is displayed automatically.
- Level measurement of a specific area is available on GPS devices. Instruments determine heights based on information received from satellites. The most accurate indicators have GPS-receivers with a built-in barometer-altimeter.
- In the search bar of the Yandex browser, type in "height above sea level" and the city, country, mountain, etc. you need. This information will be especially useful for travelers who are going to conquer mountain peaks. This way you can find out in advance what heights you will have to overcome and prepare for the ascent.
- An application called Altitude, installed on smartphones, knows how to determine the height. It determines the point above sea level in real time, as well as the speed of movement and other data. The results may not be entirely accurate with a discrepancy of one and a half to two divisions.
Also, measurements of the height of the terrain above sea level can be carried out using an altimeter - an instrument that is used to measure the heights of rise or a point above sea level. Using the altimeter is very simple:
- start the device and determine the blood pressure value corresponding to the current weather conditions;
- calibrate the device and hold down the "Set" button. After that, the device will automatically switch to the desired mode and indicate the altitude pressure at the current time;
- reduce the readings to normal using the "Set" button. Having saved the obtained parameters in the main menu, the screen will display the height above sea level of the desired object.
Altimeter - a device for measuring altitude above sea level How to find out the height above sea level using one method or another is a purely individual matter, but the altimeter will give more accurate readings in comparison with mobile applications and GPS.
Highest and lowest land area above sea level
If we talk about the highest and lowest points on a global scale, then Mount Everest, the real name of Chomolungma, belongs to the first. It is located in the Himalayan mountain system at an altitude of 8848 m above sea level. The second peak of the mountain rises at an altitude of 8760 metro.
Everest is the clear winner among all the mountains of the planet in terms of elevation. Back in the 19th century, an employee of the geodetic service Radhanat Sikdar from India measured its height. But since then, the data has changed, and the mountain turned out to be even higher than originally stated.
The lowest point above sea level is not one, but two at once. The first is on land. This is the coast of the Dead Sea on the border between Israel and Jordan. The point is located at around 417 meters below sea level, but as experts say, every year this figure increases by 1 meter.
The second point is called the Mariana Trench and is located deep under the waters of the Pacific Ocean. It is a bottomless crater, which at its lowest point is more than 11 thousand meters below sea level.
Pressure versus altitude
At different altitudes, the atmospheric pressure will also be different. Many people regularly face the problem of the close relationship between poor health and fluctuations in atmospheric indicators. For this reason, it is impossible to hike in the mountains and fly in airplanes, especially over long distances.
According to the researchers, the dependence of pressure on altitude is determined by such indicators: an increase of 10 meters causes a decrease in pressure by one mark, i.e. for every 100 m, there is an average decrease of 7.5 mm. rt. Art. Until the altitude reaches 500 meters, changes are not felt, but if you climb 5 kilometers, the values will be half the optimal value, which will affect your well-being. This is due to the liquefied air and a decrease in the amount of oxygen required for living organisms.
List of national elevation systems
Baltic height system
The system of heights used in Russia from 1977 to the present day. The heights are counted from zero of the Kronstadt footstock. Used in Russia and a number of other CIS countries.
Normalhöhennull (German. Normalhöhennull )
The height system has been used in Germany since 1992. The heights are counted from the mark on the church of St. Alexander in Wallenhorst
National Geodetic Vertical Datum of 1929 (eng. National Geodetic Vertical Datum of 1929 )
The height system used in the USA and Canada. The heights are counted according to the sea level observed in 1929 at 26 points of the North American continent (21 in the US, 5 in Canada). In 1983, it was recalculated using a new set of points and measuring mean sea level in them. The new height system is called the NAD83 standard
European Terrestrial Reference System 1989 (Italian. European Terrestrial Reference System 1989)
The height system used in Italy and a number of other European countries. The count is based on the heights of the Eurasian lithospheric plate.
Amsterdam Ordnance Datum (eng. Amsterdam Ordnance Datum )
The system of heights has been adopted since 1879 in the Netherlands. Elevation 0 is an elevation in the center of Amsterdam at 9 feet 5 inches above sea level. This height system served as the basis for Normalnull (eng. Normalnull ) and are still used today.
General historical background
The need to measure sea level has existed for a very long time. The sea level relative to land for a long observation period was taken as zero. The heights and depths of Western Europe are calculated from the Amsterdam footstock. The level of the Mediterranean Sea is measured along the Marseilles foot gauge.
In Russia, the foot-staff service was organized by Peter I. The first foot-staff appeared in St. Petersburg in 1703. Sea level measurements were necessary for the young Russian fleet - sailing in the shallow waters of the Gulf of Finland and the mouth of the Neva depended on sea level, as well as the construction of defensive structures on the island. On the mainland, at the Oranienbaum railway station, there is a mark No. 173. The results of the leveling, carried out since 1880, show that the altitude position of the zero of the Kronstadt foot stock is practically invariable.
Country history of used height systems
- Holland
- Russia: In 1840, horizontal marks were engraved on granite. They were taken as zero sea level. From now on, measurements of depths and heights have been made from the zero point of the Kronstadt foot gauge throughout the entire territory of Russia. Geographic maps are aligned to the Kronstadt reference point. Even the calculation of space orbits in the Soviet Union and later Russia is based on the level of a small line of a copper plate attached to the abutment of the Blue Bridge of the Obvodny Canal in Kronstadt.
- Italy
- France
Disadvantages of the used height systems
The Baltic system of heights, which fixed in a certain year at the zero mark, the position of the Kronshtat footstock does not reflect the change in the height of this Footstock due to the subsidence or uplift of the lithospheric plate under Kronstadt.
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From Wikipedia, the free encyclopedia
Height above sea level, absolute height, absolute mark or altitude(lat. altitudo- height (points of the earth's surface above sea level)) - one coordinate in three-dimensional geospace (the other two are latitude and longitude), showing at what level, relative to the sea level taken as zero, this or that object is located.
Examples of
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Links
- // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
- - article from the Great Soviet Encyclopedia (3rd edition)
Excerpt Characterizing Height Above Sea Level
“No… e… t,” Dolokhov said through clenched teeth, “no, it's not over,” and after making a few more falling, hobbling steps to the saber itself, he fell on the snow next to it. His left hand was covered in blood, he wiped it on his coat and leaned on it. His face was pale, frowned and trembling.- Please ... - Dolokhov began, but he could not pronounce it right away ... - please, he finished with an effort. Pierre, barely holding back sobs, ran to Dolokhov, and was about to cross the space separating the barriers, when Dolokhov shouted: - to the barrier! - and Pierre, realizing what was the matter, stopped at his saber. Only 10 steps separated them. Dolokhov lowered his head to the snow, eagerly bit the snow, raised his head again, straightened himself, picked up his legs and sat down, looking for a solid center of gravity. He swallowed cold snow and sucked on it; his lips trembled, but still smiling; the eyes glittered with the effort and malice of the last collected forces. He raised the pistol and began to aim.
“Sideways, cover yourself with a pistol,” said Nesvitsky.
- Like "oytesya!" Unable to bear it, even Denisov shouted to his opponent.
Pierre, with a meek smile of regret and remorse, helplessly spreading his legs and arms, stood straight with his broad chest in front of Dolokhov and looked sadly at him. Denisov, Rostov and Nesvitsky closed their eyes. At the same time they heard a shot and an angry cry from Dolokhov.
- Past! - Dolokhov shouted and powerlessly lay down on the snow, face down. Pierre clutched his head and, turning back, went into the forest, walking entirely through the snow and uttering incomprehensible words aloud:
- Stupid ... stupid! Death ... lies ... - he repeated, wincing. Nesvitsky stopped him and took him home.
Rostov and Denisov took the wounded Dolokhov.
Dolokhov, silently, with his eyes closed, lay in the sleigh and did not answer a word to the questions that were asked to him; but, having driven into Moscow, he suddenly woke up and, with difficulty raising his head, took the hand of Rostov, who was sitting beside him. Rostov was struck by the completely changed and unexpectedly enthusiasticly tender expression on Dolokhov's face.
- Well? How do you feel? Asked Rostov.
How many interesting things you can see by visiting Kronstadt! Founded as a fortress-defender of St. Petersburg, Kronstadt during its history literally absorbed the naval power of our Fatherland in all its manifestations. It is easy to notice when walking around the city: monuments, obelisks, weapons, military engineering structures can be found literally at every step. But even among them there are some kind of unique ones, completely unlike anything else, hiding behind themselves a whole layer of national history ...
One of these places can be found near the Blue Bridge, and for this you need to lower your gaze to its supports. It is here, where the waters of the Obvodny (Provision) Canal are splashing, that an object is located on one of the abutments, the existence of which is known to every domestic surveyor, topographer or land surveyor - the Kronstadt tide stock or ordinary.
The Blue Bridge in Kronstadt is one of the points where sightseers are invariably taken
Being metric, the tide gauge formally measures the height of the Baltic Sea water level. But in fact, this place for Russia truly plays the role of the "navel of the Earth", as Yuri Gagarin once called it. And he was absolutely right: the Kronstadt tide-rod is the zero point of the entire leveling system of Russia, it is from here that all the depths, heights and orbits of spaceships are counted.
Only after visiting Kronstadt, the first cosmonaut of the Earth learned about the existence of a reference point for the orbit of spaceships.
The tide rod itself is a cast-iron ruler with porcelain graduations of positive and negative values, and is attached to the abutment of the Blue Bridge across the Obvodny Canal. Nearby, on the granite block of the Blue Bridge parapet, there is a memorial plate for the zero point of the Kronstadt footstock. The tide-rod is complemented by a pavilion with a tide gauge, made in the form of an elegant turret, located here, next to the Blue Bridge.
Commemorative plaque about the worst flood in the history of St. Petersburg
The tide gauge is located in this pretty turret.
The footstock is a level gauge in the form of a rail with graduations that allow you to fix the water level in the reservoir. River, sea, lake footstocks are designed to solve local technical and construction problems, as well as global ones. Often, footstocks are used as geodetic reference points, studying on the basis of observations and leveling (leveling according to a conditional level) between the tidestocks the difference in sea level and the movement of lithospheric plates, entailing vertical changes in the earth's surface.
The need to measure the sea level for mankind has arisen a long time ago. The sea level relative to land for a long observation period was taken as zero. The heights and depths of Western Europe are calculated from the Amsterdam footstock. The level of the Mediterranean Sea is measured along the Marseilles foot gauge.
A worthy member of the club of hereditary footstocks is the Kronstadt one, one of the oldest in the global network of level posts of the World Ocean. In fact, the tide rod itself, as well as the tide rod service, are the same age as St. Petersburg. And this is not surprising: for the strategically convenient location of the "window to Europe" the young capital had to pay a high price: from the very moment of its foundation, the city suffered from floods. It is no coincidence that it was in St. Petersburg in 1703 that the first such device was installed. And a little later, in 1707, through the efforts of Peter the Great, a foot service was established on the island of Kotlin, where Kronstadt is located.
When it comes to St. Petersburg and its environs, the word “founder” is most often applied to Peter the first. And footwear service is no exception.
Strong fluctuations in water level necessitated regular monitoring of the indicator. This was important not only for timely warning of the population and prompt response in case of floods, but for planning navigation in the shallow waters of the Gulf of Finland and the mouth of the Neva, as well as for the construction of defensive structures on Kotlin Island.
Over the years, the practice of regular observation and footwear service has been continually improved. Since 1731, sea level observations were made in the Srednyaya harbor of Kronstadt. The footstock was installed in "ordinary water", that is, at the mean sea level at Kronstadt, which was 21 feet (6.39 m) from the bottom of the channel. The meaning of "ordinary water" was fixed in the form of horizontal lines on the walls of locks, canals and basins.
In 1752. In Kronstadt, the first Russian marine hydrographic station was opened, at which constant observations of the sea level were carried out, and in 1777, in connection with the organization of the Baltic Sea foot service in Kronstadt, observations began to be carried out using the foot stock installed in the Merchant Harbor. Then the measuring rod was on the western wall of the Merchant Harbor. And only in 1800 the tide stock was moved to the bull of the bridge over the Obvodny Canal.
Regular observations of the sea level along the foot gauge in Kronstadt began in 1806. The zero foot gauge, as in the previous period, coincided with the “ordinary water” mark, that is, 21 feet (6.39 m) above the bottom of the channel. However, the "service" as an orderly carried its own dangers, as vividly reminded of the November events of 1824.
During the famous flood from November 6 to 7 according to the old style (November 19 - new), the most severe flood in the entire history of observations fell on St. Petersburg, when the water level rose by 3 m. 67 cm above the ordinary. The city will forever remember this disaster, it was immortalized by A. Pushkin in the poem "The Bronze Horseman", and on the houses of the Neva embankments you can still find memorable badges at the middle of the second floor, where the water rose.
The memory of the flood was also noted on the Blue Bridge in Kronstadt, where a bronze commemorative plaque was installed, on which the water level was marked during this devastating St. Petersburg flood. The Kronstadt tide stock itself was demolished and subsequently rebuilt.
3.67 meters. This is how much the water rose in November 1824
The memory of the terrible November 1824 was preserved on the walls of many houses in St. Petersburg
Despite the periodic rampages of the elements, observations of fluctuations in the water level in the Gulf of Finland did not stop. On their basis, the Russian hydrographer Mikhail Frantsevich Reinecke calculated the average water level of the Baltic Sea, and in 1840 a mark was made on the stone bull of the Blue Bridge across the Obvodny Canal near the Technical School, corresponding to the zero value of the Baltic Sea level. So on the island of Kotlin, at the Blue Bridge, a Baltic orderly was registered. This innovation made it possible to observe sea level from a single zero mark. Long-term later measurements confirmed the accuracy of Reinecke's measurements; no correction was required.
We owe the appearance of the Baltic Ordinary in Kronstadt to the Russian hydrograph Mikhail Frantsevich Reinecke
In 1886, the astronomer-geodesist Fyodor Fedorovich Vitram, at the place of the zero mark, made a copper plate with a horizontal line in the stone, which represents the zero of the Kronstadt foot stock.
The last third of the 19th century was marked by innovations brought by scientific and technological progress. Since 1870, sea level has been monitored using a tide gauge - a special device for continuously recording sea level fluctuations. A little later, the tide gauge was moved to a small pavilion with a deep well, where the tide gauge recorder impartially recorded sea fluctuations, noting both ebbs and floods.
A serious achievement in observing water level fluctuations was the implementation of the leveling connection between the zero of the Kronstadt footstock with marks on the mainland.
The first leveling network on the territory of the present Leningrad Region, which includes the eastern part of the Gulf of Finland, was created at the end of the 19th century. The average level in Kronstadt, calculated over the observation period of various duration, was taken as the initial horizon of these levelings. By that time, there were a number of leveling systems named after their authors (Rylke system, Vitram system, Fusa system, Rudovitz system).
Thus, by the beginning of the twentieth century, the connection between the level of the Gulf of Finland and coastal marks (the absolute elevation of the level of the Gulf of Finland), although it was made repeatedly, but none of these zeros was finally adopted, and different departments used different data, which made it difficult to exact scientific research. The most common was zero S.D. Rylke in 1894, since a nationwide leveling network was tied to it.
To control the position of the tide stock zero, special benchmarks are used - marks on the continental land surface. The key benchmark of the Kronstadt footstock was the horizontal carving of the letter "P" in the word "Benefit" on the monument to Peter Kuzmich Pakhtusov, located not far from the Blue Bridge. The excess of the benchmark over the zero of the tide rod, according to measurements for decades, confirmed the stability of the Reinecke mark of 1840. In 1892, the already mentioned Vitram, by leveling, received an excess of the benchmark NS above the zero of the Kronstadt tide stock equal to 5.2251 m. The altitude footnote of the zero of the Kronstadt tide stock to the mainland was laid by Vitram by leveling along the Oranienbaum - St. Petersburg railway line: it was started with mark No. 173 on the building of the Oranienbaum railway station (its mark was equal to 5.4663 m above Kronstadt tide stock) and ended with a tie to a bolt mark on the wall of the passenger building of the Baltic Station in St. Petersburg in 1892. It was this bolt mark, installed by Vitram, that served at that time as the main benchmark for all levelings brought to the level of the Baltic Sea. The efforts of colleagues in the workshop were summed up by astronomer Viktor Yegorovich Fus, who carried out the final connection of the zero of the Kronstadt tide stock with marks on the mainland. Thus, the issue of the main zero of the heights of Russia was resolved.
In 1903, 1905, 1907, 1911 and 1912. Through the efforts of the head of the instrumental chamber of the Kronstadt port, Kh. F. Tonberg, the carving of the letter "P" was checked against the horizontal line on the metal plate. As a result of these determinations, the following marks were obtained: 5.2266 m, 5.2239 m, 5.2246 m, 5.2254 m and 5.2230 m.In 1913, he also installed a new plate with a horizontal line, which still serves as the starting point of the entire leveling network in Russia.
The Great Patriotic War brought new trials to the Baltic Ordinary: the Kronstadt tide-rod was badly damaged: the rail bent, even the zero-point mark was damaged. A special Interdepartmental Commission for the ordering of the Kronstadt tide stock and found its condition unsatisfactory. The Commission noted that the tide rod and the "zero board" tide rod have been launched; in winter, the tide rod and zero-point are not cleared of ice, as a result of which the level readings are made "by eye"; the pipe connecting the tide gauge well with the canal has not been cleaned for about 10 years; dipstick bent, etc.
But almost immediately after the war, on April 7, 1946, on April 7, 1946 by Resolution No. 760 of the Council of Ministers of the USSR "On the introduction of a unified system of geodetic coordinates and heights on the territory of the USSR" the Baltic Sea - the Kronstadt tide stock was taken as the initial level of heights. The Main Directorate of Geodesy and Cartography (GUGK) was entrusted with the recalculation of the leveling network into a unified system of heights, completed before 1946 (to complete the work within 5 years).
In May 1948, a decision was made to build a new century-old installation of the Kronstadt foot stock. It was also decided to close the existing zero-point plate with a safety frame and make a new metal tide rod. The interdepartmental commission discussed in detail the project of a new tide gauge installation, and in 1949 the Naval Engineering Construction Department began construction of a well and a tide gauge booth near the Blue Bridge. At the same time, other restoration and repair works outlined by the said commission were started at the object of "national importance".
Despite its outwardly ancient surroundings, the pavilion is relatively young: it was built only in 1951.
As a result, the tide gauge well, 7 m deep, was hidden in an elegant turret and is connected to the Bypass channel with a pipe about 5.5 m long and 50 cm in diameter.A modern metal level gauge rail 3.6 m and a brass zero-point footstock plate are attached to the Blue Bridge bull across the Obvodny Canal in Kronstadt near the tide gauge pavilion built in 1951. Nearby, on the granite block of the Blue Bridge parapet, there is a memorial plaque at the zero point of the Kronstadt foot stock.
In 1977, the USSR adopted the Baltic system of heights (BSV), according to which the counting is carried out from the zero of the Kronstadt foot stock. From this mark, the heights of geodetic control points were measured, which are fixed on the ground by different benchmarks and plotted on the maps. The system was secured with benchmarks of the 1st class of accuracy.
The last major changes to the Kronstadt tidestock were due to the construction of protective structures in Leningrad against floods (dam), which affected the accuracy of the readings. In order to preserve the proper accuracy of observations, on the coast of the Gulf of Finland to the west of the dam, backup lines of the Kronstadt footstock were introduced, located in Lomonosov, Kronstadt and the village of Shepelevo. In the same place, in Shepelevo, a century-old level post was also built. In the future, it is assumed that the functions of the Kronstadt foot stock will be completely transferred to the Shepelev post.
Lighthouse town in Shepelevo
Today, rare tourist groups pass without stopping at the Blue Bridge. And no wonder: the Kronstadt tide-rod is one of the oldest in the world. But this is not the main thing: where else in our country can you see the real "navel of the Earth", and even located in such "democratic conditions"? An amazing point that gives rise to all measurements of depths and heights, orbits of spacecraft? And all this is a small tablet with a line, fixed at one of the pillars of the Blue Bridge, hiding a whole layer in the history of Kronstadt and our country ...
Here it is, the starting point of the leveling network of our country!
P.S. When writing the article, the materials of the book "The Kronstadt tide stock and its Shepelevsky backup" (author - V.I.Bogdanov) were used
