### How to Measure Location, Distance and Time on Earth Surface? – Explained!

Location affects trade relationships too. The US has the largest trade with Canada and Mexico because they are the immediate northern and southern neighbours respectively. Proximity helps in faster deliveries, lower freight costs and less inexpensive servicing of buyers. One of the pressures to normalise Indo-Pak relations is the location and trade. To import pulses from Melbourne (Australia) to New Delhi will take at least 45 days, but only a week from Lahore (Pakistan)

Since the Earth’s surface is curved (not flat), it can’t be divided into a rectangular grid, we divide it using imaginary circles set on the surface that are perpendicular to the axis of rotation in one direction and parallel to the axis of rotation in other direction. Imagine a point on the Earth’s surface.

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As the Earth rotates, the point traces out a path in space, following an arc – that is a curved line that forms a portion of a circle. With the completion of one rotation, the arc forms a full circle. This circle is known as a parallel of latitude, or a parallel. The Earth’s longest parallel of latitude lies midway between the two poles and is designated the equator. The equator is a fundamental reference line for measuring the position of points on the globe.

On the other hand, if the lines are cut from one pole to the other, each cut outlines a circle on the globe passing through both poles. Half of this circular outline, connecting one pole to the other is known as meridian of longitude or simply a meridian. Meridians and parallels define geographical directions. Meridians are north-south lines, whereas parallels are east-west lines.

Latitude is an indicator of how far north or south of equator parallel is situated. The latitude of a parallel is measured by the angle between a point on the parallel, the centre of the Earth, and a point on equator intersected by a meridian passing through the point of interest on a parallel.

Equator is at 0 degree of latitude and divides the globe into two equal portions or hemispheres. To the north of equator is known as northern hemisphere and to the south of equator is designated as southern hemisphere.

The distance covered by one degree of latitude is approximately 110 km (69 miles) on Earth’s surface. To pinpoint a location more accurately, each degree is divided into 60 minutes (written: 42?) and each minute into 60 seconds (written: 26?).

Longitude is a measure of the position of a meridian eastward or westward from a reference meridian or called the prime meridian. Longitude is the angle, measured in degrees. The prime meridian passes through the location of old Royal Observatory at Greenwich, near London, England. For this reason it is also referred to as the Greenwich meridian.

It has the long value 0 degree. The longitude of a meridian on the globe is measured eastward or westward from the prime meridian, depending on which direction gives the smaller angle. Longitude, thus, ranges from 0 degree to 180 degree east or west.

Distance and direction define the relative location of one place with reference to another.

Another practical application of the Earth’s geographic grid and the rotation is global time. Since it takes 24 hours to complete a circle with respect to the Sun, a solar day is divided into 24 units, called hours. A clock is devised to keep track of hours in groups of 12. But different regions set their clocks differently. Our global time is oriented to the Sun.

The use of standard time simplifies the global timekeeping problem. In the standard time system, the world is divided into 24 time zones. In the following map 24 principal time zones of the world are shown. In the figure, 15 degree meridians are shown. The figure also shows time of the day in each zone when it is noon at the Greenwich Meridian.

China spans five time zones but runs on a single time using the standard Meridian of Beijing. Some of the countries like India keep time by a meridian that is midway between standard meridians, so that its clock departs from those of its neighbours by 30 to 90 minutes.

World time zones are numbered to indicate the number of hours difference between time in a zone and time in Greenwich. A number of +5, for example, indicate that adding five hours to local time will give Greenwich time, while a -5 hours indicates that subtracting five hours from local time will give Greenwich time.

On a world map with 15 degree meridians and count them in eastward direction, starting with the Greenwich meridian as 0, we find that the 180th meridian is number 12 and that the time at this meridian is therefore 12 hours later than Greenwich time. Counting in a similar manner westward from the Greenwich meridian, we find that the 180th meridian is again 12 but that the time is 12 hours earlier than Greenwich time. This paradox is explained by the fact that different days are observed on either side of this meridian.

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