3. Mapping the Earth's Surface

Photo 6: This is a 1767 map of my native area in Holland called "Alblasserwaard," highlighting towns and cities, townships, and the local nobility. The red Coat of Arms with the 3 arrows on the top left and bottom right are supposedly my ancestors. Most importantly this image shows that Cartography is both an art and a science. 2011-06-27

Cartography

Humans have been making maps of the Earth for a long time, the earliest records date back to 2500 BCE to a clay tablet from the Mesopotamian world. This was more a diagram outlining the most important features than a detailed map of shape, area, and scale/distance. Cartography is the art and science of map making. That this is an art is visible in photo 6 above.

Map Projections

Besides different maps for different functions, maps do not all look the same depending on the type of projection used. Cylindrical projection is most common and known as Mercator projection. This type is most accurate around the equator and the two tropics and least around the poles. Other map projections are conic projection, planar projection (used for the poles), and equal-area projection. All projection types are strong at one or two of the variables of shape, area, and scale, and weak at the others. Mercator is not good for accurately displaying area, because Africa often looks too small compared to North-America; nor is it good for displaying scale/distance, because flying from London to Toronto looks like a curve on the map and is a straight line in reality. Maintaining angels and shape is what Mercator projection is popular for today.

Photo 7: A globe. 2011-06-27

Longitude and Latitude

The most accurate projection of the Earth is on a globe, as in photo 7 above. A Globular projection of Earth is divided into north-south lines called meridians and east-west lines called parallels. The starting point for meridians is the Prime Meridian in Greenwich, Great-Britain, and for the parallels it is the equator. Distances can be measured in the degrees (°), minutes (`), and seconds (“) relative east or west of the Prime Meridian and north or south of the equator. This system is utilized by most Global Positioning Systems (GPS). Edmonton`s coordinates are 53°34′N 113°31′W.

Other coordinate systems

Besides Longitude and Latitude, there are a few other systems that can be used to define ones location on Earth. During medieval times this was the Stereographic coordinate system. A modern system developed by the military during the cold war was the Universal transverse Mercator spatial coordinate system. Locally, the Dominion Land Survey system has been used in most of western Canada to divide the land into sections of 1 square mile.