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1.5: Chapter 1 Reference Guide- Coordinate Systems, Units, Terminology

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    Earth Frameworks Reviewed

    The Earth is not a sphere, but it is pretty close to one. The distance between the center of the Earth and the north and south poles differs by about 20 km, so the Earth is referred to as an oblate spheroid. Let's review some terminology and frameworks that will be used during the course of this book:

    Cartography

    Figure \(\PageIndex{1}\) shows the Geographic coordinate system for the Earth. Meridians, which are north-south lines on a globe, are given by degrees of longitude. Think of the distance between the north and south poles as long.

    • The prime meridian passes through Greenwich, Great Britain, at 0 ° longitude.
    • East of here (defined as the Eastern Hemisphere, 0 – 180 °E), longitude is positive.
    • West of the prime meridian (Western Hemisphere, 0 – 180 °W), longitude is negative.
    • The Earth rotates counterclockwise about its axis.
    The Geographic coordinate system.
    Figure \(\PageIndex{1}\): Longitude lines are perpendicular to, and latitude lines parallel to, the Equator. (Public Domain; Fedstats via Wikimedia Commons)

    Parallels, which are east-west lines on a globe, are given by degrees of latitude. A good way to remember this is “Lat” rhymes with “flat” — just like the east-west horizontal (flat) lines of latitude.

    • The Equator is 0° latitude,
    • Latitudes north of the Equator are positive (Northern Hemisphere: 0 – 90°N), and
    • Latitudes south of the Equator are negative (Southern Hemisphere: 0 - 90°S).

    A helpful approximation is that each degree of latitude is approximately 111 km, or about 60 nautical miles.

    This page titled 1.5: Chapter 1 Reference Guide- Coordinate Systems, Units, Terminology was last modified on Wed, 02 Sep 2026 04:08:26 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Neel Desai and Alicia Mullens.