Part one: Latitude and longitude
The first time you walk across the equator, that imaginary line that separates the Earth into two spheres, you get a sense of place, your location. The north and south poles would create the same recognition.
Navigation is not just about which way you need to go; it is also about understanding where you are on the back roads. Where am I now?
For Canadians, the 49th parallel means a lot. Our position in the world is relative, something that has been known for a long time. It’s time for a little schooling.
Within the Back Roads Bill stories, there are always location coordinates and/or a map link to the My Maps app. These given coordinates are often referenced like this: Zone 17 T E 663576 N 5129113 and N 46° 17.870' Long. W 78° 52.567’. These coordinates are important to how to effectively and efficiently navigate. In essence, Global Positioning System (GPS) and digital maps have made us, using the informal use of the word, “dumb,” our spatial awareness is waning. We trust the little triangle cursor, the “pin” or the original voice of GPS to voice our turns on the streets and highways.
Our smart devices, for the most part, default to decimal degrees because they are absolute numbers and when there is no legal or proper noun address digital mapping tends to break down, especially on the back roads.
Need to know
When you step away from your cell phone and digital mapping apps there is the question: “Why is knowledge of latitude and longitude more important to a pilot or a ship's captain than to a bus driver?
At one time or another, most of us have used a city map to find the location of a street. Such maps are usually divided by vertical and horizontal grid lines. The grid spaces formed by these lines are designated along one margin by letters and along the other by numbers. A combination of letters and numbers, such as "B-5,” indicates the square formed by the intersection of column B and row 5; it is here that the desired street is to be found. That’s a good starting point for comprehension.
What if you are somewhere with no landmarks? There are two systems or spatial languages, latitude and longitude and the Universal Transverse Mercator (UTM) contains numbers and units of measure used to explain where we are, relative to fixed lines. For some time now I have been asked to explain this in easy terms. So here goes, part one latitude and longitude and it is not complicated and they are called geographic coordinates.
Claudius Ptolemy was a Greco-Egyptian mathematician, astronomer and geographer. His main work is the creation of geography (also called the geographia), a compilation of geographical coordinates of the part of the world known to the Roman Empire during his time. He first devised and provided instructions and foundations on how to create maps. This grand scheme, based on scientific principles, assigned (x,y) numbers to all the places and geographic features he knew, in a grid that spanned the globe. Latitude was measured from the equator, as it is today. He used degrees and put the meridian of 0 longitude at the most western land he knew and this was the beginning of an organized and logical navigation system; others would refine this. None of this is new.
What eventually evolved was the equator, halfway between the poles and the one fixed artificial line, the Greenwich Meridian, which runs from the North Pole to the South Pole through Greenwich, England.
Every location on Earth has a global address. Because the address is in numbers, people can communicate about location no matter what language they might speak. A global point is given as two numbers called coordinates. The two numbers are a location's longitude number and its latitude number ("lat./long.”). Just as an aside when you Google "latitude/longitude" you get 10 times more results than "longitude/latitude". It is very confusing as "x/y" is more common than "y/x". But on a map or chart latitude is on the Y axis and longitude on the X. The equator was determined astronomically before the Prime Meridian and they didn’t agree on its location until 1884. Before the units, we most often have E and W (longitude) and N and S (latitude) that place us in one of the four quadrants of the lat./long. of the coordinate plane. So it became latitude and longitude (reversed from the mathematical convention.)
Using lat./long. is different from using a street address. Instead long. /lat. works with a numbered grid system, like what you see when you look at graph paper. It has vertical and horizontal lines that intersect with the four cardinal directions. A location can be mapped or found on a grid system simply by giving two numbers which are the location's horizontal and vertical coordinates or the "intersection" where the place is located.
Latitude is the Y axis, longitude is the X axis. Since latitude can be positive and negative (north (+) and south (-) of the Equator), and longitude can be as well (negative west of Greenwich and positive eastward) when the -180 to +180 longitude system is used. Hence the four combinations of positive and negative are possible depending upon where you are located on the globe.
The beauty of using lat./long is that a point referenced anywhere on the Earth’s surface is like a specific signature, increasing west or east of the Prime Meridian and increasing north or south of the equator. (In Canada coordinates of latitude can only be N (+) and longitude can only be W (-).
Latitude - parallels
Horizontal mapping lines on Earth are lines of latitude. They are known as "parallels" of latitude because they run parallel to the equator. One simple way to visualize this might be to think about having imaginary horizontal "hula hoops" around the earth, with the biggest hoop around the equator, and then progressively smaller ones stacked above and below it to reach the North and South Poles.
Latitude lines are a numerical way to measure how far north or south of the equator a place is located. The equator is the starting point for measuring latitude - that's why it's marked as 0 degrees latitude. The number of latitude degrees will be larger the further away from the equator the place is located, all the way up to 90 degrees latitude at the poles. Latitude locations are given as __ degrees North or __ degrees South of the equator.
Vertical mapping lines on Earth are lines of longitude, known as "meridians.".
One simple way to visualize this might be to think about having hula hoops cut in half, vertically positioned with one end at the North Pole and the other at the South Pole.
Longitude - meridians
Longitude lines are a numerical way to show/measure how far a location is east or west of a universal vertical line called the Prime Meridian. This Prime Meridian line runs vertically, north and south, right over the British Royal Observatory in Greenwich England, from the North Pole to the South Pole. As the vertical starting point for longitude, the Prime Meridian is numbered 0 degrees longitude.
To measure longitude east or west of the Prime Meridian, there are 180 vertical longitude lines east of the Prime Meridian and 180 vertical longitude lines west of the Prime Meridian, so longitude locations are given as __ degrees east or __ degrees west. The 180-degree line is a single vertical line called the International Date Line, and it is directly opposite of the Prime Meridian.
To precisely locate points on the earth's surface, degrees of longitude and latitude have been divided into minutes (') and seconds ("). There are 60 minutes in each degree. Each minute is divided into 60 seconds and it has nothing to do with time but angular measurement. Seconds can be further divided into tenths, hundredths, or even thousandths.
There was great difficulty in measuring longitude. British clockmaker and carpenter John Harrison invented a portable marine chronometer that allowed ships to calculate longitude while at sea during the 18th century. There is an entire TV movie here that explains it.
Degrees and measurement
For example, a coordinate might be written in three ways. Degrees can be expressed as a decimal degree, 65.5375° N; degrees and decimal minutes: 65° 32.25 ' N or even degrees, minutes and decimal seconds: 65° 32' 15.275" N. For the most part mariners and our electronic devices use degrees and decimal minutes. Surveyors like the break down into seconds.
Only at the equator are the unit values for lines of latitude and longitude almost the same. Lines of longitude, because of the Earth’s curvature will change slightly in value moving north and south. Lines of latitude do stay the same (parallels) until they approach the poles (do not worry about this distortion only if you are journeying close to the poles!) Each degree of latitude is approximately 111 km (69 miles) apart; there is a variation due to the fact that the earth is not a perfect sphere but an oblate ellipsoid (slightly egg-shaped). This is possible because a minute of latitude is equal to every other minute of latitude on the globe. Notice, that since meridians or lines of longitude, are not parallel then minutes of longitude change their length as we move north or south. In fact, minutes of longitude are always smaller than minutes of latitude except right at the equator where they are almost equal. (One minute of latitude is defined as one nautical mile. A nautical mile corresponds to a little more than a statute mile.)
Although latitude has an obvious zero line at the equator, longitude has no recognizable zero line. Mapmakers could choose an arbitrary line, usually a known longitude within their country. Ptolemy chose to have the zero-longitude line pass through the Canary Islands. Later chosen were Paris, Rome, St Petersburg, and Philadelphia, among others. Finally, in 1767, the world began to use London, specifically the observatory in Greenwich outside London.
A little homework. This week’s assignment pick your favourite place and determine the lat./long. in the three formats. You can do it because from a safety perspective knowing the location with coordinates may be the only way of communicating your location. Send your answers by a stamped postcard!
And if you would rather have a visual tutorial this is how the kids learn about lat./long. In just a few minutes, trust Ali the Alien character within.
Next week it is UTM (Universal Transverse Mercator), an easier system to navigate, you will discover what zone you are in.
So far so good, class is ended, and consider knowing or recognizing both spatial languages on the back roads.
