Latitude, Longitude and Coordinate System Grids

Horizontal Datums

Here’s how you can remember latitude and longitude:

Latitude lines run east-west. They are parallel to each other. The further north you go is determined by latitude. And latitude values (Y-values) range between -90 and +90 degrees

Longitude lines run north-south. They converge at the poles. And X-coordinates are between -180 and +180, which are called longitudes.

Latitude and longitude coordinates make up a spherical coordinate system.

Map Coordinate Systems

Real world objects can be located on Earth by coordinate systems.

Various coordinate reference systems exist. In each coordinate system, geographic locations or features are described mathematically using coordinate values.

A geographic coordinate system defines three-dimensional coordinates based on the Earth’s surface. It contains an angular unit of measure, prime meridian and datum (which contains the spheroid).

Longitudes:
X-coordinates are between -180 and +180, which are called longitudes.
Longitude Coordinates
Longitude Coordinates
Latitudes:
Y-values are between -90 and +90 degrees, which are lines of latitudes.
Latitude Coordinates
Latitude Coordinates

Most horizontal datums define a zero line at the equator. The equator is where we measure north and south.

The Greenwich Meridian (or prime meridian) is a zero line of longitude from which we measure east and west. The zero line passes through the Royal Observatory in Greenwich, England – which is how it earned its name. In a geographical coordinate system, it is a line of longitude defined to be 0°.

Most horizontal datums define a zero line at the equator. The equator is where we measure north and south. The Greenwich Meridian (or prime meridian) is a zero line of longitude from which we measure east and west.

Prime Meridian

Together, these lines provide a reference for latitude and longitude that zig-zag into each other.

This system is also known as a geographic grid. All points on our planet can be referenced with this geographic grid in latitude and longitude coordinates.

Orthographic

Locate ANYTHING on Earth with Coordinates

Coordinates are pairs (X, Y) or triplets (X, Y, Z) of values that are used to represent points and features on a two and three-dimensional space. The X-value represents the horizontal position and Y-value represents the vertical position. The Z-value generally refers to the elevation at that point location.

Coordinate Grid

Geographic coordinate systems (latitudes and longitudes) are based on a spheroid surface. Spheroids are approximate locations on the surface of the earth. The datum defines the surface. The major axis (longest diameter of an ellipse) and minor axis (shortest diameter of an ellipse) and radius represent the position of the surface relative to the center of the earth.

What is a Coordinate Reference System?

Reference ellipsoids are mathematical models of the shape of the Earth with the major axis along the equatorial radius. A geographic coordinate system uses longitude and latitude expressed in decimal degrees. WGS 1984 and NAD 1983 are examples of datums.

Coordinates are pairs (X, Y) or triplets (X, Y, Z) of values that are used to represent points and features on a two and three-dimensional space.

Globe: New York to Tokyo

Spherical coordinates (latitudes and longitudes) are often written as degrees-minutes-seconds (DMS). Minutes range from 0 to 60. For example, the geographic coordinate expressed in degrees-minutes-seconds for New York City is:

  • Latitude: 40 degrees, 42 minutes, 51 seconds N
  • Longitude: 74 degrees, 0 minutes, 21 seconds W

Geographic coordinates can also be expressed in decimal degrees. Here is New York City in decimal degrees:

  • Latitude: 40.714
  • Longitude: -74.006

Latitude, Longitude and Spherical Coordinate System Grids

When you put two coordinates together as a pair (X, Y), anything on Earth can be located.

Latitude and longitude form our coordinate system grids.

They can be expressed in different ways such as in decimal degrees and degrees-minutes-seconds.

Thanks to our geographic coordinate everything on Earth can be pinpointed, including the spot you are reading this article rifght now.

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