How is the time difference between two countries calculated? - Times of India
the relationship between the portion of Earth being studied and Earth as a whole . the time in that time zone encompassing the prime meridian, or 0 degrees the theory that the physical environment may set limits on human actions, but. Positions and coordinates, latitude, longitude, Nautical mile, Mercator, plotting a In the same way that we divide hours of time into minutes and seconds, we also should you lose your electronics and the boat's nav aids are out of action. Geography examines the spatial relationships between all physical and cultural He devised one of the first systems of longitude and latitude and calculated the The natural forces of erosion, weather, tectonic plate action, and water have look at spatial (space) and temporal (time) relationships between many types of.
No means is perfect, and over the centuries people have tried different ways.
For sailors though the Mercator Projection is the best way to see the world on a chart. In the Flemish geographer and cartographer Gerardus Mercator published a map for sailors that enabled them to plot a course in straight lines on a chart, a breakthrough for marine travel. Until then, maps were largely drawn for people as guides and were largely pieces of artwork. Instead of the longitude lines diverging at the poles and converging at the Equator, these have been straightened into parallel lines like the latitude lines.
The world is therefore not a globe but a square.
How are longitude lines and time zones related? | Socratic
There are problems with the Mercator projection: Europe appears to be of similar size to Africa, when Europe is just a third the size. Only around the Equator is the projection accurate as this is where the projection is laid out from — everything north and south seems bigger than it actually is.
You will also have paper charts in reserve. Plotting a course In a recent article Kavas Yachting covered the basics of how to do manual coastal navigation should there be a problem with your electronic navigation aids. That describes how to plot a three-point fix, how to do Dead Reckoning and an Estimated Position.
It might be fun for the kids or inexperienced crew to do some manual coastal navigation as you sail on Greek waters.Longitude and Time
For children it can show them the relevance of trigonometry that they learn in their school maths lessons to the real world! For someone new to sailing it may help to demystify some of the dark arts of seamanship.
Planning a course between Greek islands Here is one example of paper navigation. Most navigation courses will require you to buy or possess a Breton Plotter and a pair of dividers. The Breton Plotter has a compass rose and different lines that can be used for navigation on a chart. At its simplest it is a pair of parallel lines so you can slide it around the chart as you do your calculations. The compass rose is a plastic circle with degrees marked out around it on an oblong piece of plastic that measurements on it.
To plot a route from the fairway buoy of your departure harbour to the fairway buoy of your destination you would align North on the Breton Plotter with North on the chart, and then calculate the Variation this could be 10 degrees or so according to the position of Magnetic North relative to True North — find out in your Nautical Almanac. You then slide the Breton Plotter down to the two harbour buoys and, with the rose pointing Magnetic North, turn the main plotter to the route you will need to travel.
You will then be able to read off the course you will need to travel from the plotter compass rose.
Time and The Sun Clock: Figuring It Out
As you do your route, you can do three point fixes, EPs and DR to measure just where you are compared to the proposed route. Perhaps you may have an inexperienced helm, or the boat has a lot more leeway than you expected? A fix on the chart can tell you exactly where you are and you can adjust your route accordingly.
Magnetic North is the top of a vast magnetic field that runs from hundreds of miles above the South Pole to hundreds of miles above the North Pole.
It protects the Earth from cosmic rays that could otherwise destroy our electronics and give us skin cancers. In this story the number 12 keeps coming up.
Another useful thing about 12 is that it is easily counted on your hand. In this system you have units and 12s, instead of units and 10s. Units of 12 can easily be counted with your fingers. Hours, minutes and seconds, then degrees, minutes and seconds, how did we end up with this apparent confusion of shared terms with different measures? However their independent study and recording from multiple civilisations and societies produced a range of options, some quite similar but others are quite diverse in their logic.
It was up to the path of history to define the choice of what survived and what passed into the background. Distance If we look at distance around the globe first, any direct east west travel follows a circular path of latitude. So one degree of longitude at the equator measures nearly km, but gradually reduces to zero at the poles as you travel on latitudes north or south of the equator. How did this come about, as degrees are used for any angular measurement between two lines, not just for circles?
Maybe someone was thinking beyond the square when they realised the obvious — as any angular measurement between two lines increases, the lines move apart in a circular path and eventually meet up again as they complete the full circle — it happens all the time on your analogue watch.
Latitude, Longitude and Time Zones - the Earth's Coordinate System
But returning to degrees. The origin is not known and only guessed at. The Persian calendar was one example that had a day year. Equilateral triangles with 60 degrees at each corner, then divided up into The Greeks followed suit, and there is evidence the Indians were also using a unit circle.
For many purposes a degree is sufficient definition, but it was then further subdivided with the sexagesimal base into 60 minutes and 60 seconds. In recent time a decimal based degree system was proposed but never adopted, however radians which help with calculations have been long accepted, but we seem to have avoided them in longitude, where distance is measured in degrees, minutes and seconds. The notion that the graphical concept of the time span for both one day and one year could each be described as a following a circular path was one for the deep thinkers, and some of these early astronomers and philosophers probably concluded there was a spherical nature to earth and its relation to the sun as they pondered the whole picture.
For most people life went on not over a curved surface on a sphere travelling in a huge circle, all they could see was a flat ground going nowhere and the priority was wanting to know what was happening with time during the daylight period. A year and its divisions into days were easy enough to put start and end points to, but dividing the day did not workout easily as daylight lengthened and shortened daily to a pattern repeated each year, rather than neatly staying the same for each day.
Some aspects of the divisions related to stars to help mark the progress of night, but the day was locked onto the sun. The word 'hour' has evolved from referring to the board span of the seasons to a specific unit of time.
But why 60 of each? The answer is not written down in any history, and how it came to be remains speculative, but go back to a clock or watch and remember the counting system of 12 on the finger joints and 5 on the fingers, the 60 based system.
The circular track of a clock face featuring 12 hours, with 5 divisions between each creates 60 divisions all round. And it works rather neatly — the hour hand labours on slowly, a minute hand can gradually move around ticking off time 60 times faster, while the second had does it another 60 times quicker again, all using the same grid around the circumference.