Section Four - Latitude and Longitude - One Example of a Geographic Grid

For as long as humans have had the goal to explore our planet, they have also had the need to devise a navigation method to make this process easier, and more importantly, a method which was reliable and repeatable. As these exploration and discovery missions took explorers over longer distances and away from land, which is super handy for sighting back to and knowing where you are, a world-wide system that could be used day or night was needed. With a rather long history of discovery, trail, and error, latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° and longitude became a world-wide grid system, giving an explorer the ability to know where they were at all times, with a general error of about 10 feet. Not too bad without a GPS receiver!

Geographic grids are created when a grid is applied to the Earth (initially a sphere for easy measuring, as we will see in this section, then later, that sphere is transformed into an ellipsoid) and the intersections are labeled via a Cartesian Coordinate system method. In this section, we will look at the specifics of creating that grid, by first by creating a sphere-based Earth-centered, Earth-fixed coordinate system (EFEC coordinate system) Earth-centered, Earth-fixed coordinate systems use the center of the Earth as a start point for measurements, while local-north systems use a smaller area affixed to the Earth’s surface as the start point). ECEF coordinate system require us to select a principle meridian (the north-south line from which to establish the X origin point, aka the place to start counting) and an before laying out the grid. Since the goal of an ECEF coordinate systems is to label locations on a 3D sphere, we can't efficiently use a linear unit of measure, like feet or meters. As we will see when the lines are drawn and the labels placed, using angles to establish measurements will be a boatload easier than using linear units, which would only be accomplished by wrapping an imaginary cloth tape measure around the Earth, which wouldn't lay flat, and really only measure the circumference, and what would the circumference even tell us .... you get it ... or you will when we look at establishing the line of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° and longitude.

longitude is an and is just one example of a geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. , utilizing a specific principle meridian, the Prime Median, and degrees measurement of plane angle, representing 1⁄360 of a full rotation (circle). In full, a degree of arc or arc degree. Usually denoted by ° as the angular unit of measure the selected units for measuring angles.  Choices include degree and radians.  to label and later be able to navigate to locations on the Earth’s surface.

Geographic grids, it should be noted, are not a complete geographic coordinate system nor are they a datum. Latitude and longitude, albeit the most common - is not the only geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. out there. All of this reading is working towards the established goal of creating a tied down, worldwide "address system" we call a geographic coordinate system. The GCS is made up of two parts, one of which is a datum (which we will look at in the next section) and the other of which is geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. (which we are about to see requires an ECEF Coordinate System to be transformation into a reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid ).

2.4.1: Cartesian Coordinate Systems

A Cartesian coordinate system An equally spaced grid that exists in a single geometric plane where intersections of perpendicular lines are labeled with the count of units from a specified origin (0,0) point , created by René Descartes in 1637, is defined as an equally spaced grid that exists in a single geometric plane where intersections of perpendicular lines are labeled with the count of units from a specified (0,0) point. You most likely learned all about Cartesian Coordinate Systems in grade school or jr. high. Each grid has a 0,0 point at the origin of the system, and each intersection of the X and Y lines are labeled according to how far said intersection is from the origin.

In cartography and GIS, each datum has an origin and labeled points where the X and Y (and since datums are 3D, the Z) lines intersect. In the next section we will look at one method of labeling those intersections using latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° and longitude, but for now we will just look at how the 2D XY values reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid is connected to the 3D Z value geoid a model of the variation between global mean (average) sea level and local mean sea level the measurement above or below the global average at a single point on the Earth's surface used for recording the elevation of topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." 's relief the difference between the highest and lowest point within a particular area while landforms are the descriptive words for individual features , which is used to measure precise elevations on the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." .

2.4.2: Latitude

Lines of Latitude ( latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° (n.) late 14c., "breadth," from Old French latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° (13c.) and directly from Latin latitudo "breadth, width, extent, size," from latus "wide,") or parallels are the east-west portion of the grid, running horizontally - along the horizon. Using the Equator as a starting point for the geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. , historically, latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° was easier to compute and comprehend than longitude (north-south lines), as splitting the Earth in half in the middle was simple to understand and easy to start with. Starting at the Equator, lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° use an angle system based upon a right triangle, encircling the earth at each of the 90 degrees measurement of plane angle, representing 1⁄360 of a full rotation (circle). In full, a degree of arc or arc degree. Usually denoted by ° North and South. The best way to understand how lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° are labeled is to look at the process it takes to create the lines from scratch.

Creating Lines of Latitude from Scratch, Step 1. Draw the Earth as a Circle and Cut the Circle in Half
If we draw the Earth as a circle, then bisect that circle (cut in half in the exact middle), we have defined three things already: The Equator (equa = equal; tor = a suffix to make an adjective do an action; thus: the equal maker) The Northern Hemisphere (hemi = half; thus: half a sphere) The Southern Hemisphere

Sidebar: Let’s state a few more facts before we move on.

We know the Earth rotates around a central axis, a single line that connects the North and South Poles right through the center of the sphere. Let’s mark the North and South poles on our drawing. Since we are dealing with circles, it’s best to define sections with angles, which are measured in degrees measurement of plane angle, representing 1⁄360 of a full rotation (circle). In full, a degree of arc or arc degree. Usually denoted by ° (I promise this will be a very short visit back to 10the grade geometry). Great. We have drawn: A sphere (the Earth) A single point at the top and bottom of that sphere (the North and South poles) a line bisecting that sphere right in the middle (the Equator) And we’ve decided to use a method of measuring parts of that sphere Angles measured in degrees measurement of plane angle, representing 1⁄360 of a full rotation (circle). In full, a degree of arc or arc degree. Usually denoted by °

Creating Lines of Latitude from Scratch, Step 2. Establish the Equator as 0°

Lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° are labeled by the angle which is created from the North Pole to the center of the circle representing the Earth, then from the center of the circle back to the edge somewhere between the North Pole and the Equator. To determine the latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° of the Equator, draw a straight line from the North Pole to the center of the circle and out to the edge right at the Equator (which in our drawing, already exists as the Equator itself). The angle created, according to that 10the grade geometry, is 90° - thus the latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° of the Equator is: 0° latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° ; and by default, the North Pole is at 90° latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° .

Step 3. Mark all the angles between 0° and 89° and connect them from east to west

If we add in each angle from 1° to 89°, then from that point, draw a straight line to the other side of our circle, we see we’ve created a series of 90 parallel lines running from the North Pole to the Equator, or the lines of Northern Latitude. If we mark a point representing Denver, we would need to start at the Equator and count up 39 lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° , then drop the point. To create the lines of Southern Latitude, we simple repeat this process starting at the South Pole and moving up. When labeling lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° , all lines in the northern hemisphere have an ‘N’ tacked on, while all the lines in the southern hemisphere have an ‘S’ tacked on. The Equator is in neither the northern nor the southern hemisphere, thus gets no label of N or S.

2.4.3: Longitude

Lines of longitude (late Middle English (also denoting length and tallness): from Latin longitudo, from longus ‘long.’) or meridians are similar to latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° in the fact they divide the Earth into equal parts, but a different due to the fact that all lines of longitude all pass through the North and South poles, creating what looks like a spider web when viewed from the top down. The convergence of lines at the North and South poles results in the distance between lines of longitude not being an equal measure of 69 miles for the entire distance like lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° , but a variation between 0 miles at the poles and 69 miles at the Equator.

To solve for the variation, multiply either 68.972 miles or 111 kilometers by the cosine of the latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° for which the longitude measurement is being taken. For example, Denver, CO is at 39° 44" 31.3548' N, 104° 59 29.5116" W. To find the distance between the lines of longitude (in this case, 104° and 103° or 105° along the 39the parallel), first find the cosine of the latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° (cosine of 39° = 0.777), then multiply it by 68.972 miles (68.972 * 0.777) which would equal 54.38 miles. In other words, if you walked north along 104° W from the 38the to the 39the parallel, you would walk 68.972 miles, and if you continued the journey on the the 40the parallel, you would walk another 68.972 miles. However, if you were to walk west along the 39the parallel from 104°W to 105°W, you would walk 54.38 miles. If you moved that journey north one degree of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° and walk west along the 38the parallel from 104°W to 105°W, you would only walk 54.33 miles (68.972 * 0.788), a difference of only 0.03 miles, but indeed a shorter distance.

With lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° , there is a logical start point: divide the sphere in half creating the equator. But when it comes to lines of longitude, the part where the divisions are made by drawing a line from the North to the South pole is logical, deciding where to put the zero line, or the prime meridian, is a bit less obvious. So a place was chosen - Greenwich, England⁵.

While lines of latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° are measured as angles between the North (or South) pole and the equator, angles which measure lines of longitude start at the Prime Meridian the name of the principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. in the latitude/longitude system and travel along the Equator marking each degree to the west until the reaching the other half of the Prime Meridian the name of the principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. in the latitude/longitude system , this creates 180 marks (and moving from the Prime Meridian the name of the principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. in the latitude/longitude system east makes a maximum of 180 marks east, for a total of 360 degrees measurement of plane angle, representing 1⁄360 of a full rotation (circle). In full, a degree of arc or arc degree. Usually denoted by ° , a full circle)

Creating Lines of Longitude from Scratch, Step 1. Draw the Earth as Circle.

First, we are going to draw a new circle to represent the Earth. Since we are looking down at the North Pole from space, we are going to place a single dot right in the middle of the circle to represent the North Pole. Since we know the Prime Meridian the name of the principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. in the latitude/longitude system passes through Greenwich, we will mark the location with a dot. At this point, the circle can be bisected with a line passing through Greenwich.

Step 2. Fly around the globe along the 51st Parallel to create a 90° angle

When you hop into your plane in Greenwich, England and begin to fly east, if you maintain that bearing, you will be flying along at 51.4° N, or approximately the 51st parallel. If you complete a 90° angle, you will land in Russia, just north of Mongolia . Mark this point, and bisect the circle with a line passing through the point in Russia. Note the other half of the circle passes through a very remote part of Ontario, Canada. Label it 90° W between the North and South Poles on the left side of the circle, and 90°E on the Russian side.

Step 3. Continue your flight to make a 180° angle
If you continue your flight to complete a half circle, you will land somewhere in the middle of the Bearing Sea. You will be on the opposite side of the planet from Greenwich, at 180° No need for W or E, as it is simply labeled 180° from the North to the South pole. Between the North and South poles on the Greenwich side, the line of longitude is labeled 0°. Again, no need for W or E.

Step 4. Add all of the angular measurements between 0° and 180°, then bisect the circle
At this point, we need to mark all of the angular measurements between 0° and 180°, remembering we are still looking down at the North Pole from space. Bisect the circle at each of the remaining 178 locations (since we started with 0° and 180°, and marked 90° in step 2)

Step 5. Add all of the labels using the idea of supplementary angles

In geometry, supplementary angles add up to 180. Lines of longitude are supplementary angles in reference to Greenwich. If we are looking down on our labeled circle and we choose any point we've marked, then draw a straight line through the circle, we see the angle in the west to be supplementary to angle in the east. In this same fashion, lines of longitude are labeled with one measurement in the west (between the North and South poles) and the supplement of that angle in the east (also, between the North and South poles).

2.4.4: Creating a Complete Geographic Grid

Now that we have looked at how the Earth-fixed, Earth-centered coordinate system is established for latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° and longtiude, we need turn the sphere-based system in to an ellipsoid based system to complete the geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. . We learned in Section Three that the Earth is best represented by an ellipsoid of revolution, more specifically, an oblate spheroid a sphere-like object which is wider than it is tall and the geoid a model of the variation between global mean (average) sea level and local mean sea level the measurement above or below the global average at a single point on the Earth's surface used for recording the elevation of topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." 's relief the difference between the highest and lowest point within a particular area while landforms are the descriptive words for individual features , which is used to measure precise elevations on the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." is best represented by an ellipsoid. In Section Four, we learned the definiton of a geodetic datum the result of attaching a "free-floating" reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid to a specifically measured geoid a model of the variation between global mean (average) sea level and local mean sea level the measurement above or below the global average at a single point on the Earth's surface used for recording the elevation of topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." 's relief the difference between the highest and lowest point within a particular area while landforms are the descriptive words for individual features , which is used to measure precise elevations on the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." via control points and benchmarks. is combining a geoid a model of the variation between global mean (average) sea level and local mean sea level the measurement above or below the global average at a single point on the Earth's surface used for recording the elevation of topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." 's relief the difference between the highest and lowest point within a particular area while landforms are the descriptive words for individual features , which is used to measure precise elevations on the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." with a reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid , connecting them via control points. In order to keep on-track with our definitions, we need to transform the sphere used to create the EFEC latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° /longitude coordinate system into not an oblate spheroid a sphere-like object which is wider than it is tall , as we are not trying to represent the Earth, but instead into an ellipsoid to best-fit inside the geoid a model of the variation between global mean (average) sea level and local mean sea level the measurement above or below the global average at a single point on the Earth's surface used for recording the elevation of topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." 's relief the difference between the highest and lowest point within a particular area while landforms are the descriptive words for individual features , which is used to measure precise elevations on the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." via a method called affine transformation. Affine transformation is a means of changing a sphere into an ellipsoid while maintaining straight lines.

After we took all the time to carefully create the lines of latiude and longitude and we understand they are used to grid-out and label locations on the Earth's surface, we'd like to take that hard work and preserve it over in the reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid . All we are really doing is linearly streching the measurement of the radius into a semi-minor and a different semi-major axis. By increasing the measurements of the radius, we are able to create an ellipsoid without curving the straight lines.

The Main Point...

Our overall goal is to create a geographic coordinate system. To accomplish that, we need to first create a datum, which combines a geoid a model of the variation between global mean (average) sea level and local mean sea level the measurement above or below the global average at a single point on the Earth's surface used for recording the elevation of topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." 's relief the difference between the highest and lowest point within a particular area while landforms are the descriptive words for individual features , which is used to measure precise elevations on the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." and a reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid , since an ellipsoid is a better representation of a geoid a model of the variation between global mean (average) sea level and local mean sea level the measurement above or below the global average at a single point on the Earth's surface used for recording the elevation of topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." 's relief the difference between the highest and lowest point within a particular area while landforms are the descriptive words for individual features , which is used to measure precise elevations on the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." . A reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid is really just an plain old ellipsoid until a geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. has been applied to it, and that geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. starts out as an Earth-fixed, Earth-centered coordinate system, such as the latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° and longitude system. After the EFEC system is complete, it is necessary to use and affine transformation to "convert" the sphere into an ellipsoid. An affine transformation maintains the straight lines of the latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° /longitude system between the sphere and the ellipsoid.

2.4.5: Null Island: A Real Fake Place

ATLAS OBSCURA: WWW.ATLASOBSCRUA.COM Null Island is One of the Most Visited Places on Earth. Too Bad It Doesn’t Exist The ocean spot is the center of the world’s geocoded map mistakes. BY TIM ST. ONGE MAY 09, 2016 The ocean spot is the center of the world’s geocoded map mistakes. It doesn’t seem like much of a place to visit. Granted, I’ve never actually been there, but I think I can imagine it: the vastness of ocean, overcast skies, a heavy humidity in the air. No land in sight, with the only distinguishing feature being a lonely buoy, bobbing up and down in the water. It almost seems like a “non-place,” but it may surprise you to learn that this site is far from anonymous. This spot is a hive of activity in the world of geographic information systems (GIS). As far as digital geospatial data is concerned, it may be one of the most visited places on Earth! This is Null Island. Artistic fantasy map of Null Island. Graphic by Ian Cairns on GitHub 2013. Null Island is an imaginary island located at 0°N 0°E (hence “Null”) in the South Atlantic Ocean. This point is where the equator meets the prime meridian. The exact origins of “Null Island” are a bit murky, but it did reach a wide audience no later than in 2011 when it was drawn into Natural Earth, a public domain map dataset developed by volunteer cartographers and GIS analysts. In creating a one-square meter plot of land at 0°N 0°E in the digital dataset, Null Island was intended to help analysts flag errors in a process known as “geocoding.” Geocoding is a function performed in a GIS that involves taking data containing addresses and converting them into geographic coordinates, which can then be easily mapped. For example, a data table of buildings in Washington, DC could include the Madison Building of the Library of Congress (where I’m reporting from) as a feature and include its address: 101 Independence Avenue SE, Washington, DC, 20540. This address typically makes sense to the layperson, but to put the address on a map using a GIS, the computer needs a translation. A “geocoder” converts this address into its location as set of coordinates in latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° and longitude, a format that a GIS understands. In this case, the Madison Building’s geographic location becomes 38° 53′ 12′′N, 77° 0′ 18′′W (38.886667, -77.005 in decimal degree format). Anyone who has ever typed in an address on Google Maps or looked up driving directions on MapQuest has been a beneficiary of this tool: type in an address, get a pin on a map. Unfortunately, due to human typos, messy data, or even glitches in the geocoder itself, the geocoding process doesn’t always run so smoothly. Misspelled street names, non-existent building numbers, and other quirks can create invalid addresses that can confuse a geocoder so that the output becomes “0,0”. While this output indicates that an error occurred, since “0,0” is in fact a location on the Earth’s surface according to the coordinate system, the feature will be mapped there, as nonsensical as the location may be. We end up with an island of misfit data. The zero latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° , zero longitude location of “Null Island”-fame is based on the World Geodetic System 1984 (WGS84), a commonly-used global reference system for modeling the Earth that is the standard for the Department of Defense and the Global Positioning System (GPS). Technically, if you were geocoding in another coordinate system or map projection technically: the result of using one of variety of methods to transfer the geographic locations of features from a geographic coordinate system to a developable surface everyday use: any coordinate system, geographic or projected (which are essentially different frameworks for adapting the Earth onto a sphere, ellipsoid, plane, or other shape for measurement and mapping), the position of “0,0” could be in one of thousands of locations around the world (A fun mapping experiment by Kenneth Field, Craig Williams, and David Burrows goes further down this rabbit hole). But for most standard geocoding, chances are, if you’ve ever geocoded less-than- perfect data and didn’t check your results, some of your data points have probably visited this one peculiar spot in the Gulf of Guinea. Sending geospatial data points off to Null Island, so to speak, is a recognizable sight among GIS professionals the world over. As a cartographer in the Geography and Map Division with quite a bit of geocoding experience under my belt, this phenomenon is certainly familiar to me. This shared experience among geographers has fed the mystique of Null Island, with GIS enthusiasts creating fantasy maps, a “national” flag, and articles detailing Null Island’s rich (and fake) history online. The mystique, of course, is all just in good fun, although plenty of maps in the Geography and Map Division are just that: fantasy maps originating from one’s own imagination and communicating interesting perspectives on art, culture, and technology. That said, you may still be thinking that the significance of the location of Null Island is little more than a geographer’s inside joke. But remember that lone buoy? That’s Station 13010 (also known as “Soul”), a NOAA weather observation buoy. Permanently anchored at 0°N 0°E, Soul collects data on air temperature, water temperature, wind speed, wind direction and other variables as part of the Prediction and Research Moored Array in the Atlantic (PIRATA) program. Observations collected by Soul and other buoys in the PIRATA network support research into climatic conditions and weather forecasting in the Tropical Atlantic and beyond. An ATLAS buoy from the PIRATA program, similar to the one at the “Null Island” site. Photo by National Data Buoy Center, National Oceanic and Atmospheric Administration. Null Island is a curious blend of real and imaginary geography, of mathematical certainty and pure fantasy. Or it’s just the site of a weather observation buoy. However you see it, we have the GIS world to thank for putting Null Island on the map...in its own, strange way.

2.4.6: Additional Resources for Latitude and Longitude

YouTube Break: The Clock That Changed the World

An explanation of using time for navigation (the longitude problem) and satellite navigation ( trilateration the process of determining absolute or relative locations of points by measurement of distances, using the geometry of circles, spheres or triangles. ... In contrast to triangulation, it does not involve the measurement of angles ).

Run Time: 29 minutes "arc minute" 1/60th of a degree. Usually denoted by " , but really well done and quite interesting. Highly recommended to better understand the geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. that is longitude and latitude also known as 'parallels' the east-west portion of a geographic grid measured with angles between 0 and 90° .

• Note: SatNav = GPS Receiver

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