Latitude and longitude, respectively: each represented as a decimal number. Note that negative latitudes represent the southern hemisphere, and negative longitudes represent the western hemisphere. In our example, 0. A longitude is an angle from the prime merdian, measured to the east longitudes to the west are negative. Latitudes measure an angle up from the equator latitudes to the south are negative.
Figure 1. With an angle of longitude and an angle of latitude, we can locate any point on the surface of the earth. You've seen lines running across maps your whole life and may not have noticed them. Determine whether numbers are negative or positive. When using the degrees and decimal minutes system, you do not use directions like north, south, east, and west. Instead, you use positive and negative numbers to determine where locations fall on a map.
Remember, lines of latitude fall north or south of the equator. To the east, the numbers increase until degrees on the other side of the earth from London. To the west, the numbers decrease until degrees meets degrees in the middle of the ocean.
When we put latitude and longitude together, they form a pair of numbers that can be plotted on a map. When using decimals to indicate latitude and longitude, positive numbers fall north of the equator and negative numbers fall south of the equator.
Most of mathematics prefers radians to degrees, and in fact GIS software, like Excel or Matlab, actually will use radians for angular computations. There are many conventions for how to record latitude and longitude, and they present challenges for a computer. To avoid problems, unless a program explicitly prompts or allows to use use minutes or second, you should always use decimal degrees; it is easy to use a spreadsheet to convert if necessary.
Positive coordinates are to the right east and up north. This means that the Western Hemisphere has negative longitudes.
0コメント