Why are coordinates important

Yeah, me too! Give yourself some credit, you know what this SRS is all about too! Geographic coordinate systems are super common, especially when dealing with data that spans continents or the entire globe. Unlike Cartesian type coordinate systems, which are localized and somewhat arbitrary, geographic coordinate systems work worldwide. The numbers within the geographic coordinates can give the experienced geographer an instant idea of where those coordinates point to on the globe.

You can think of Geographic Coordinate Systems as breaking the globe up into 4 sectors, or hemispheres. The basis of this is latitude and longitude.

Lines of latitude are the horizontal lines on a globe, representing how far north or south you are from the equator northern and southern hemisphere. These lines are often referred to as parallels. The lines that run vertically are for measuring longitude, this means they tell you how far east or west you are of the Prime Meridian eastern or western hemisphere which is located at 0 o.

As you may have imagined, lines showing longitude are referred to as meridians. The Prime Meridian could be anywhere, as it is just an arbitrary starting point, but the official Prime Meridian was designated in and is located at the Royal Observatory in Greenwich, England, which is in London. Geographic coordinate systems measure out from the center of the earth and find the angle between the core and the surface see the image to the upper left which results in your location being represented in either degrees, minutes, and seconds, or in decimal degrees.

Image Credit: Encyclopedia Britannica. Image Credit: The Greenwich Meridian. Degrees, minutes, and seconds are units of measurements going from largest to smallest, allowing you to get very granular with your location, or just keep it general. There are o surprise, surprise!

Degrees can then be can be broken down into 60 minutes, and a minute can be broken down into 60 seconds. So, if you are familiar with the format, you can get a general idea of where you are just based on the numbers.

In this example, I can see that the first number is positive, which means northern hemisphere. The next number is negative, that tells me it is in the western hemisphere, and since it is o I know from experience it is on the east coast of the US. As you may have picked up on from the address, this is the White House in Washington D.

This is much different than the Cartesian coordinate system — coordinates from those, such as UTM, are arbitrary remember that false easting conversation? Decimal degrees are like degrees, minutes, and seconds, just in a different format. Nearmap can provide you with both coordinates just by dropping a pin on the map within MapBrowser TM.

This is because everything comes through in square tiles using Web Mercator — the earth is broken up into a series of grid squares. Web Mercator, despite its popularity, is a very poor projection and introduces a lot of size and distortion errors which we will discuss further. Ironically, the Mercator projection was never meant to be a projection used to map land. The unique advantage of the Mercator projection is that azimuth lines are constant — this means that you could follow your compass in a straight line and never have to make any other adjustments.

In a nutshell, Mercator was meant for navigating the seas, but has become the universal standard projection for most web mapping applications! There are some neat applications out there that do a really good job of showing that distortion from Web Mercator. One of my personal favorites is thetruesize.

This is because with Web Mercator, as you move away from the equator, either north or south, areas will get stretched out and appear larger than they should be.

Image Credit: TheTrueSize. With that being said, you can see how this might cause some issues for end-users. A position defined by the coordinates 1,1 is located one unit to the right, and one unit up from the origin 0,0. The Universal Transverse Mercator UTM grid is a widely-used type of geographic plane coordinate system in which positions are specified as eastings distances, in meters, east of an origin and northings distances north of the origin.

Some coordinate transformations are simple. The transformation from non-georeferenced plane coordinates to non-georeferenced polar coordinates, described in further detail later in the chapter, shown below involves nothing more than the replacement of one kind of coordinates with another.

The geographic coordinate system grid of latitudes and longitudes consists of two curved measurement scales to fit the nearly-spherical shape of the Earth. As discussed above, geographic coordinates can be specified in degrees, minutes, and seconds of arc.

Curved grids are inconvenient to use for plotting positions on flat maps. Furthermore, calculating distances, directions, and areas with spherical coordinates is cumbersome in comparison to doing so with plane coordinates. For these reasons, cartographers and military officials in Europe and the U. UTM grids are now standard not only on printed topographic maps but also for the geographic referencing of the digital data that comprise the emerging U.

The act of mathematically transforming geographic spherical coordinates to plane coordinates necessarily displaces most but not all of the transformed coordinates to some extent. Because of this, map scale varies within projected plane UTM coordinate system grids. Thus, UTM coordinates provide locations specifications that are precise, but have known amounts of positional error depending on where the place is.

Shown below is the southwest corner of a ,scale for which 1 inch on the map represents ft. The tick on the west edge of the map labeled "" represents a UTM grid line called a "northing" that runs parallel to, and 4,, meters north of, the equator.

Ticks labeled "" and "" represent grid lines that run perpendicular to the equator and , meters and , meters east, respectively, of the origin of the UTM Zone 18 North grid see its location on Fig 6 above. Unlike longitude lines, UTM "eastings" are straight and do not converge upon the Earth's poles. The Universal Transverse Mercator system is not really universal, but it does cover nearly the entire Earth surface.

Polar coordinate systems are used to specify positions beyond these latitudes. The illustration above depicts UTM zones as if they were uniformly "wide" from the Equator to their northern and southern limits.

To clarify this, the illustration below depicts the area covered by a single UTM coordinate system grid zone. Each UTM zone is subdivided along the equator into two halves, north and south. The illustration above shows how UTM coordinate grids relate to the area of coverage illustrated above. The north and south halves are shown side by side for comparison. Each half is assigned its own origin.

The north south zone origins are positioned to south and west of the zone. North zone origins are positioned on the Equator, , meters west of the central meridian for that zone. Origins are positioned so that every coordinate value within every zone is a positive number. This minimizes the chance of errors in distance and area calculations.

By definition, both origins are located , meters west of the central meridian of the zone in other words, the easting of the central meridian is always , meters E. These are considered "false" origins since they are located outside the zones to which they refer.

UTM eastings specifying places within the zone range from , meters to , meters at the equator. These ranges narrow toward the poles. Northings range from 0 meters to nearly 9,, in North zones and from just over 1,, meters to 10,, meters in South zones. The distorted ellipse graph below shows the amount of distortion on a UTM map.

This kind of plot will be explained in more detail below; the key thing to note here is that the size and shape of features plotted in red indicate the amount of size and shape distortion across the map a wide range in sizes indicates substantial area distortion, a range from circles to flat ellipses indicates substantial shape distortion.

The ellipses centered within the highlighted UTM zone are all the same size and shape. Away from the highlighted zone, the ellipses steadily increase in size, although their shapes remain uniformly circular.

This pattern indicates that scale distortion is minimal within Zone 30, and that map scale increases away from that zone. What are the coordinates of the missing vertex? Answer: -3, 1. In this diagram, R is an equal distance from P and Q. What are the coordinates of R? Answer: 50, This diagram shows two identical rectangles on coordinate axes. Write the coordinates of point A and point B. Here is a kite. Write the coordinates of point D.

A counter is placed on square D4. It is moved 2 squares right and 3 squares down. Write the position of the square it lands on. Answer: F2. Learn more or request a personalised quote to speak to us about your needs and how we can help. Our online tuition for maths programme provides every child with their own professional one to one maths tutor. What Does "Geographic Location" Mean? How to Find a Plane With 3 Points. What is the Unit Circle in Trigonometry? How to Find the Inequalities From a Graph.

What Is the Geographic Grid? Real Life Uses of the Pythagorean Theorem. How to Calculate Azimuth. How to Find Linear Equations. How to Calculate the Outside Length of a Circle. What Tools Are Used in Geography?

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