what whould you use to measure distance east and west of prime meridian

Lines of longitude, as well called meridians, are imaginary lines that divide the Earth. They run north to south from pole to pole, just they measure the distance east or west. Longitude is measured in degrees, minutes, and seconds. Although breadth lines are e'er equally spaced, longitude lines are furthest from each other at the equator and meet at the poles. A transcript is bachelor that describes this infographic content in plain text. (Epitome credit: iStock)

Prime Meridian vs. International Reference Top

Unlike the equator (which is halfway between the Globe'southward north and southward poles), the prime meridian is an arbitrary line. In 1884, representatives at the International Summit Conference in Washington, D.C., met to define the tiptop that would represent 0 degrees longitude. For its location, the conference chose a line that ran through the telescope at the Royal Observatory in Greenwich, England. At the time, many nautical charts and time zones already used Greenwich as the starting bespeak, so keeping this location made sense. Just, if you go to Greenwich with your GPS receiver, you'll need to walk 102 meters (334 anxiety) eastward of the prime number pinnacle markers before your GPS shows 0 degrees longitude. In the 19th century, scientists did non have into business relationship local variations in gravity or the slightly squished shape of the World when they determined the location of the prime superlative. Satellite technology, all the same, allows scientists to more precisely plot meridians and then that they are straight lines running north and south, unaffected past local gravity changes. In the 1980s, the International Reference Meridian (IRM) was established as the precise location of 0 degrees longitude. Unlike the prime number meridian, the IRM is not a fixed location, merely will continue to motility as the Earth's surface shifts.

Lines of longitude, also called meridians, are imaginary lines that divide the Earth. They run northward to south from pole to pole, but they measure the distance east or due west.

The prime summit, which runs through Greenwich, England, has a longitude of 0 degrees. It divides the Globe into the eastern and western hemispheres. The antimeridian is on the opposite side of the Globe, at 180 degrees longitude. Though the antimeridian is the ground for the international date line, actual date and fourth dimension zone boundaries are dependent on local laws. The international appointment line zigzags effectually borders near the antimeridian.

Like latitude, longitude is measured in degrees, minutes, and seconds. Although latitude lines are alway as spaced, longitude lines are furthest from each other at the equator and encounter at the poles. At the equator, longitude lines are the same distance apart as latitude lines — one degree covers most 111 kilometers (69 miles). Simply, by 60 degrees north or south, that distance is downwards to 56 kilometers (35 miles). By ninety degrees north or south (at the poles), it reaches null.

Navigators and mariners have been able to measure latitude with bones tools for thousands of years. Longitude, however, required more than advanced tools and calculations. Starting in the 16th century, European governments began offering huge rewards if anyone could solve "the longitude trouble." Several methods were tried, only the best and simplest manner to measure longitude from a ship was with an accurate clock.

A navigator would compare the time at local noon (when the sun is at its highest point in the heaven) to an onboard clock that was gear up to Greenwich Mean Time (the fourth dimension at the prime meridian). Each hour of difference betwixt local noon and the time in Greenwich equals 15 degrees of longitude. Why? Because the Earth rotates 360 degrees in 24 hours, or fifteen degrees per hour. If the dominicus's position tells the navigator information technology's local noon, and the clock says back in Greenwich, England, information technology'due south two p.one thousand., the two-hour difference ways the ship's longitude is 30 degrees due west.

But aboard a swaying ship in varying temperatures and salty air, even the most accurate clocks of the age did a poor job of keeping time. It wasn't until marine chronometers were invented in the 18th century that longitude could be accurately measured at sea.

Accurate clocks are still critical to determining longitude, but now they're plant in GPS satellites and stations. Each GPS satellite is equipped with ane or more atomic clocks that provide incredibly precise fourth dimension measurements, accurate to within xl nanoseconds (or 40 billionths of a second). The satellites broadcast radio signals with precise timestamps. The radio signals travel at a constant speed (the speed of light), then nosotros can easily calculate the distance between a satellite and GPS receiver if we know precisely how long information technology took for the signal to travel between them.

On the basis, NOAA's National Geodetic Survey manages the Continuously Operating Reference Stations Network, which comprises one,800 stationary, permanently operating GPS stations. These CORS continuously receive GPS radio signals and incorporate that data into the National Spatial Reference Organization. The GPS position on a smartphone is accurate to within about 5 meters (xvi feet), but processed CORS data can provide longitude accurate to inside a few centimeters, along with breadth and height positions.

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Infographic Transcript: Longitude

• The left image shows the Earth tilted on its axis. The equator and the Greenwich acme line (prime elevation) are labeled. A department has been cut away to show longitude lines (or meridians) that run vertically around the Earth. These start at the Greenwich tiptop line and are labeled from 0 to 90 degrees east. Boosted lines are fatigued from the centre of the Earth to each labeled meridian. These illustrate that the longitude measurement for each point equals the angle fabricated betwixt a line from it to the centre of the earth and ane drawn through the plane of the prime tiptop. Virtually the South Pole, an arrow indicates the direction of the Earth's rotation on its centrality.
• The correct prototype shows the Earth with the North Pole at the centre of the epitome. At this angle, the Greenwich meridian line runs straight upwards and downwards, with 0 degrees longitude labeled at the bottom of the image. The antemeridian (180 degrees longitude) is found directly at the top of the prototype. The left one-half of the prototype is labeled Western Hemisphere and the right half labeled Eastern Hemisphere. Meridians are labeled around the Earth, from 0 to 180 degrees on the west side and from 180 back to 0 on the east.

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Source: https://oceanservice.noaa.gov/facts/longitude.html