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Latitude Longitude Geographical Coordinates

Latitude and longitude are two important geographic coordinates that will tell you your exact location anywhere on the planet. An average reader may find it boring and difficult to understand when they see the terms latitude and longitude. I am positive that is going to change by the time you read this article. I will teach you the fundamentals of latitude longitude geographical points of the earth, as well as to how you can utilize such information.

Let’s take things one by one starting with latitude and then longitude.

LATITUDE

Latitude lines encircle the earth and are equally spaced, or distributed, parallel to the equator. They are also referred to as parallel lines.The equator is shown as a horizontal line that divides the earth into north and south hemispheres. Latitude lines reflect the distance going to some point of either north, or south, of the equator.

Each latitude line has its corresponding degree. Your starting point for latitude will be the earth’s equator. At the equator, the degree of latitude is zero, and the numbers  become larger the farther north, or south, you go.

The farthest points from the equator are the North and South Poles:

1. North – 90^o ABOVE the equator (90^o N)
2. South – 90^o BELOW the equator (90^o S)

This system was originally used by sailors as a tool to guide them across the oceans.

LONGITUDE

Longitude is based on a vertical line that divides the earth into east and west hemispheres, called the prime meridian, or also the Greenwich meridian. Lines, also referred as meridians, encircle the earth in equal proportions parallel to the prime meridian. They show the distance at any given point, east or west, of the prime meridian.

Unlike latitude, longitude’s basis is the prime meridian. At this point, the longitude degree is zero. It lies perpendicular to the equator.  Lines of longitude intersect  both north and south poles. So the lines get closer to each other going  north or  south.

Do not forget to locate whether you are east or west when you use longitude in determining geographical locations.

1. East – go RIGHT from the prime meridian
2. West – go LEFT from the prime meridian

Distance in between Lines

In order to calculate the distance of each latitude longitude degrees, the earth circumference should be divided by 360 degrees. The earth circumference is approximately 25, 000 miles. Using the formula above, you can compute 25, 000 ÷ 360 = 69.4^o.

Thereby, each degree of latitude, or longitude, is 69 miles or 111 kilometers. For longitude this applies only at the equator.

Precise Measurements

Latitude longitude geographical points can be measured with accuracy. The following will be used to do so:

• Degrees – (^o)
• Minutes – (‘)
• Seconds – (“)

In one degree, there are 60 minutes (1^o = 60 min); and one minute has a total of 60 seconds (1 min = 60 secs).

Let us try to use this to locate a certain area. For example, let us take a look at Monterey in Los Angeles, California. Using the above principle, its location is 36 degrees, 36 minutes North of the equator; and 121 degrees, 54 minutes west of the prime meridian (36°36′ N, 121° 54′ W). Another example is the main office of the World Atlas which is in Galveston Island, Texas. Their point of location is 29 degrees, 16 minutes, 22 seconds North of the equator; and 94 degrees, 49 minutes, 46 seconds West of the prime meridian (29° 16’ 22” N, 94° 49’ 46” W).

Both latitude and longitude are special coordinate systems which can locate a certain geographical point of the earth through the use of map or gps navigation system.

MAP DATUM

Map Datum is a model that resembles the earth. Mathematical calculations are greatly considered to approximate the shape of the earth as well. This device is designed to help people locate the exact, or approximate, position of a certain area, thing, or person. How is this possible? Well, the map datum has the capacity to calculate areas and locations in a more consistent, and precise manner.

There are specific ground points which, physically, represent the map datum. The positions of these points are measured and calculated accurately.

The latitude and longitude lines on a map will be the reference of a map datum. This means that every map has the map datum reference. You can see it in a map listed in the title block.

There 2 types of map datum that are commonly used:

1. North American Datum of 1987 (NAD27)

This datum is based on the ellipsoid model of Clarke in 1966, wherein it locates the center mass of the earth via satellite orbits. North America has chosen this to have the best fitting surface, and they used this one to orient it at a certain point in Central USA. The main ground point, or position, of this datum is located in Meades Ranch, Kansas. The control network surveys from this point towards all the areas across North America.

However, this datum is being leveled up to a more specific model called NAD83. This model is created with much mathematical adjustments. The basis for this is the Geodetic Reference System of 1980, wherein sophisticated satellites are used to measure the size and shape of the earth. With the sophistication of electronic equipments used, the measurements accurately resembled the earth to within 2 meters.

2. World Geodetic Survey of 1984 (WGS84)

The geodetic datum characterizes the size and shape of the earth, as well as the origin and direction of the coordinate systems used to map the earth. This is commonly used in navigation and cartography. It also represents the earth in ellipsoid manner. The big difference is that it uses the center of the earth as its point of reference of the whole earth, including the oceans and atmosphere.

The modern-day used device inspired by WGS84 is what we call as the Global Positioning System, or GPS. GPS uses WGS 84 as its frame for broadcast which even started way back on January 23, 1987. It is a very much sophisticated navigation system that has about 24 orbiting satellites placed by the United States of America. The principle here is that the satellites send signals to locate certain geographical points more accurately.

Now, if you want to compare GPS against chart, or map, the map datum of GPS should be modified in a way that it matches the map datum of the map itself. This will give you a more accurate comparison between the two. Do not forget that the map datum in each chart, or map, is located in its legend.

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