Orientation paper and compass
Simple cartographic maps were known already in 'antiquities. Eratosthenes (276-195 BC), a milestone in the history of cartography, first introduced the concept of parallel. Strabo later developed the work of Eratosthenes, introducing the meridians too. Today there are dozens of types of cartographic maps, political, physical, themes, nautical, a large and small scale, and so on. We see with order such are the fondamental elements of a modern
Cardinal points.
First of all, remember the cardinal points: north (top of the reader), and then, clockwise, East (right), South, and West. The figure also shows the intermediate points; North is marked in red to remind you that the 'magnetic needle of a compass always points to the North.
The ancients, who did not have a compass, oriented themselves with the sun, which in the fall and spring rises in the east and sets in the west (in the middle of winter is in the south-east and sets in the southwest, and in summer is north -east and sets in the northwest). Today we are in the fall, and then, if you were ancient travelers on the road in an area with no data points, you should orient the map turning the tip East toward the sun, so you can easily find the location on the territory of the other points. In the absence of the sun (in a forest, on a day with the sky covered by clouds), oriented themselves observing the trees, more developed on the south side, where they receive the most sun during the 'year.
With the development of knowledge and technology, we now have for the orientation of sophisticated digitized equipment for both onshore movements, and both the shipping and aviation (the routes). But there are also other utilizzii: for example, rescue missing persons, excursions, scientific and war targeting systems, cell phones with GPS, etc. Think of the chaos if only for a moment borne out maps and compasses!
geographic grid.
Parallels and meridians form the geographic grid, due to which and 'possible to determine the exact position of a place on land or in the sea by its geographical coordinates, ie latitude and longitude. Obviously, it should be clarified well that statement, and that is what we will do now! In the figure, the numbered lines, parallel and perpendicular, respectively, are the parallels and meridians.
Parallel, and latitude.
As we said, the horizontal lines are parallel. They are circles equidistant from each other, the length of which decreases as one approaches the poles. The parallels are 180, 90 to 90 north and south of the greater parallel of all, the 'equator, also said parallel 0 (zero). L 'equator is the maximum circumference of the globe, and' at the same distance from the poles and divides the earth into two hemispheres: the 'northern hemisphere on top of' equator and southern hemisphere below. The number of parallel determines the latitude, ie the distance from the equator. Depending on whether it is a meridian north or south of the equator is called latitude north or south latitude. Other important parallels are: north of the equator, we have the Tropic of Cancer and the Arctic Circle, while to the south we have the Tropic of Capricorn and the Antarctic Circle.
Meridians, and longitude
.
The vertical lines are the meridians, semicircles of the same length that pass through the poles, and divide the earth's surface into segments. They are a total of 360, numbered from the prime meridian, reference, which passes through Greenwich, a suburb of London, where and 'located the' Royal Observatory in Greenwich. The Greenwich meridian is identified with the number zero, and is also said meridian 0. From it there are 180 positive meridians to the east, and 180 negative meridians west. The number of each meridian indicates the longitude, the distance of a place 'by the prime meridian measured in degrees (... that definition will specify soon!).
Geographical coordinates of the 'Royal Greenwich Observatory are the following: 51.476465, 0.000000 That straight line in the figure passes through the pair of young people is the physical representation of a tiny section of the imaginary circumference, the said meridian 0, passing through the poles and for Greenwich. This line runs throughout the Blackheath Avenue - ... I strolled there using Street View! - The beautiful park of the "Royal Burroughs of Greenwich", where there are an astronomical observatory, l 'University of Greenwich, and the "National Maritime Museum Gardens". 'S high scientific value and for its beauty, this place is visited by many tourists. The pair of tourists' image pose standing right on the line, and it's funny to think that he and she (boyfriends, spouses, friends? ... I do not know!) Are close physically but distant geographically, being each in different hemispheres!
Question about measurement of latitude and longitude.
Since the surface of the earth is curved, a distance on it is measurable exactly only in degrees (a measure in Km. And mt. Is incorrect!). The latitude of a point (place) is obtained by measuring the arc in degrees of the terrestrial meridian between that point and the 'equator. L 'arc PA subtends the' POA corner. If the point P is located exactly on a parallel, for example 60 °, then this is its latitude; vice versa - if usually more frequent -, are also used tenths and hundredths of a degree to also represent the intermediate points. The longitude of a point (place) is obtained by measuring the arc in degrees of the terrestrial parallel between that point and the Greenwich meridian. The 'PC arc behind the' angle PBC. If the point P is located exactly on a meridian, for example 10 °, then this is its longitude .; conversely, - as for latitude -, they are also used tenths and hundredths of a degree to also represent the intermediate points.
To better understand the concepts of latitude and longitude, we think of them as two fans that can be opened only from one side, while the 'other side is fixed: the range (angle) POA, to light green, is the latitude of P , and has for fixed side perpendicular to the segment OA 'terrestrial and axis passing through the center; the range (angle) PBC, one dark green, representing the longitude of P, and has for the fixed side CB segment, which happens to be perpendicular to the Earth 'and point C axis also belonging to the Greenwich Meridian (meridian 0). If we imagine to move the point P on the earth's surface, we realize that the range of the latitude can open up to maximum of 90 ° both above and below of 'equatoere, while that of the longitude to the maximum of 180 °, both in right (+) or left (-) of the meridian 0. Now have fun! We open googlemaps, we insert in the pair search box 0,000000,0,000000 values: the green arrow appears on the World Map of googlemaps (minimizing a lot!) In the Gulf of Guinea (Atlantic Ocean), of course the line of 'equator ( and mathematician -> ... and at the same time) on the Greenwich meridian. Obviously, the two fans in this point P (point of origin latitude and longitude) are both closed. Little questions - How are the fans as follows: P (0,000000,180,000000); P (90.000000,0,000000); P (-90.000000,0,000000)? What about on the following two points: P (0,000000,180,000000); P (0.000000, -180.000000)? Now that you understand the play, you can practice by yourself!
Around the World with googlemaps
Dear Ale, first learn to derive the geographic coordinates of a point on Google Maps. then we open the page and in the search box, insert the word "Colosseum". Draw near with zoom, do right click on the point that interests us, and then, in the drop-down menu that appears, we still click "What c 'is here?"; at the point where we clicked right, you will see a green arrow, and simultaneously in the googlemaps search box appear immediately the latitude and longitude. We copy and paste somewhere the value pair. The result should be to 'about the following: Colosseum -> 41.890276,12.492307. Obviously, also it applies the reverse path. In fact, after you close and reopen Google Maps, if we insert the pair of values in the search box, reappears the 'image of the Colosseum. You can now have fun with any place at will: your house, my house, your school, that of Georgia and Giulia, etc .; you just plug the 'exact address, and repeat the process that I described. We are now ready to go around the world in less than a minute. We can, for example, starting from 'Royal Observatory in Greenwich, then point to the east keeping us on the same parallel, and then return to the starting point on the opposite side. Taking appropriately the values of geographical coordinates, we can for example verify that the longitude takes all values from 0 to 180, which are positive throughout the 'western hemisphere, and negative in the east. In fact, the Royal Greenwich Observatory (51.477454, -0.000393) -> Khabarovsk Krai, extreme eastern Russia (50.958427,134.941399) -> Atlantic Ocean, near the border with the Pacific (52.696361,167.636712) -> Pacific Ocean, near the border with the 'Atlantic (52.696361, -179.355476) -> Calvert Island, Canada (51.572802, -128.155746) -> Newfoundland and Labrador (52.321911, -59.604494) -> in the Atlantic Ocean (52.268157, -32.27051) -> Lambeth, district London, just a few Km. from Greenwich (51.49421, -0.110092) - Royal Observatory Greenwich (51.477454, -0.000393).
Using the Compass: fundamental operations.
The technical guidance - described in the guide that is normally released to 'act out' purchase - differ depending on the type of compass. Below we briefly describe what to do for a chart compass. To orient - as shown - map and compass towards the north, you must first turn the compass until the indicator of 'Azimuth * does not match the magnetic north indicated by' needle, and then rotate the map to align the lines of the grid to the compass. (L '* Azimuth is the angle between the North and our direction between the point that we are and the point we want to achieve). Now, geographic map (map) and compass are both well-oriented to magnetic north.
Assuming that "A" is our position and "B" the destination, we can now determine the direction to follow. So, let's get in front of the map with the compass in front of us. Holding the compass rotate the movable ring of the compass to align the North corresponding to 'Azimut with North reported by' magnetic needle.
Now, always making sure to maintain parity between the north of the ring with the magnetic north, just walk around holding the compass in front of us, until you reach the destination point.
Epilogue.
Today technological development provides us with many useful tools. I refer to the cell phone with GPS. Cha remember as a young man told my father to start on Alburni, then I would have reached my car to casone Farina, where we had to prepare the camp for the "three days" hunting the boar. My father persisted in bringing my son Alfredo, who was then seven max eight years, and slept all in a sleeping bag around a big fire, waiting for the first glimmering of 'Dawn' s start of the hunt. mythical times.
Walking fast, catch phrases my ankle. He could end badly, as I was stuck without being able to move.
Fortunately, my father in law he passed casually over there with the whole group .. incavolatissimo was against me, and I still remember what I said, "you go to the mountains at least two, and with the right shoes" But , with GPS I would solve everything! Therefore, dear grandchildren, by adults, if you happen to go hiking or traveling in sparsely inhabited territories, then remember to bring with you always map, compass and mobile phone with GPS.
Grandpa Zeferino
