Geography and cartography fundamentals

Cartography

The geographic coordinate system basically refers to longitudinal and latitudinal lines and the reference points on them. The lines of longitude and latitude are based on the Earth's polar axis. Latitude lines are parallel to the equator, and are measured in degrees, with the equator's value set at 0 degrees. From the equator to each of the poles there are ninety latitude lines, for a total of 180. Latitudes north of the equator are distinguished from lines south of the equator, which divides the earth into the north and south hemispheres. Latitude lines are parallel to the Earth's polar axis and are therefore also referred to simply as parallels.

Longitude lines are perpendicular to latitude lines. They are drawn parallel to the arbitrarily created Prime Meridian, which runs through Greenwich, England and therefore establishes the reference point for international time zones as well. Like latitude lines, longitude lines are also measured in degrees. There are a full 360 longitude lines on the globe, but the maximum value of a longitude line is 180, denoted by the International Date Line. The International Date Line is therefore halfway around the world from the Prime Meridian. Longitude lines west of the Prime Meridian are deemed part of the Western Hemisphere, and those East are part of the Eastern Hemisphere and are denoted as such: 60 degrees West.

2. The Universal Transverse Mercator (UTM) grid system, unlike the geographical coordinate system, is based on a flat rectangular and metric coordinate system. First the Earth is modeled according to the Transverse Mercator projection system into a two-dimensional image. Then the Earth is divided into sixty segments of six degrees longitude each. Measurements start at the International Date Line. Therefore, the UTM system relies on the geographic coordinate system for its points of reference. The UTM system is displayed on most topographical and geological survey maps in North America.

3. Map scale is a ratio between the actual distance between two points on Earth and the distance between those two points as represented on the map. Map scales vary considerably. Measuring distances using a map can be done simply using a ruler and then converting the measurement to actual distance using the map's scale ratio. However, this only works well if the distance between the two points can be measured in a straight line. Opisometers can measure the distances between two points using curved lines.

4. Direction is usually measured in relation to the north and south poles. However, the magnetic poles differ from the geographic poles. A magnetic compass can be used to measure angles relative to magnetic north. Those measures can then be translated to geographic map poles that describe True North or Grid North. The azimuth system depicts direction in terms of degrees on a circle, with north as either 0 or 360 degrees. The bearing system divides directions into quadrants, with north, south, east, and west as major reference points.

5. Standardized time keeping evolved as a result of globalization and improved transportation systems between remote localities. In 1878, a Canadian named Sir Sanford Fleming proposed the system of time zones that is still extant today, albeit with some variations due to national boundaries.

6. Topographic maps represent various three-dimensional structures and objects on a two-dimensional surface. They can depict natural features like land and sea elevations using contour lines. Contour lines distinguish areas of similar elevation on the map. If contour lines are spaced close together, it would indicate a steep elevation gain or loss. Topographic maps also use standardized symbols to represent natural and human-made structures like bridges, roads, and railways as well as swamps and waterfalls.