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Map Basics
See also: Map Collection Contents: ScaleScale is the relationship between distance on the map and distance on the ground. For example, a 1:24,000 scale map means that for every 1 inch on the map, it represents 24,000 inches on the ground. In order for a map to fit onto a sheet of paper, all the rivers, roads, mountains, etc. contained must be shown proportionately smaller than they really are. Thus, The scale of a map dictates how much information can be shown. A small scale map (e.g. a 1:1,000,000 map of the world) shows a large area but without much detail. A large scale map (e.g. a 1:20,000 map of a city) shows a small area and includes a lot of detail. Remember the saying "the larger the number, the smaller the scale."
For more information see: ProjectionsProjection refers to the mathematical method by which the three-dimensional Earth's surface is being portrayed onto a two-dimensional piece of paper (or computer file). There are many variations, but there are three types of projection methods on which all others are based: Conical, Cylindrical, and Azimuthal. Each method distorts the globe differently. For more information, see:
Geographic Coordinate System (Latitude / Longitude)The geographic coordinate system uses degrees of latitude and longitude to describe a location on the earth's surface. Latitude, marked on maps by horizontal lines called parallels, is measured in degrees either north or south of the equator. Longitude, marked on maps by vertical lines called meridians, is measured in degrees either east or west of the prime meridian (usually Greenwich, England). Each degree of latitude or longitude is divided into 60 minutes; each minute is divided into 60 seconds. An example of these geographical coordinates is 39°12' 00'' N and 120°42' 00'' W. The same coordinates can also be given as decimal degrees, for example, 39.2° N and 120.7° W or 39.2° and -120.7° (west and south are shown as negative). In the decimal degree system the degrees are the same, but rather than using minutes and seconds, smaller increments are represented as a percentage of a degree. To convert coordinates between Degrees, Minutes, Seconds and Decimal Degrees, see:
For more information see:
Universal Transverse Mercator (UTM)The UTM system divides the earth into 60 north-south zones, excluding the polar regions. UTM zones are numbered 1 through 60, starting at the international date line (longitude 180°) and proceeding east. Each zone covers 6 degrees of longitude and is divided into horizontal bands of 8 degrees of latitude. These bands are lettered, south to north, beginning at 80° S with the letter C and ending with the letter X at 84° N. See Peter H. Dana's UTM Zone Numbers map. To convert between geographic coordinates and UTM:
For more information see:
Public Land SurveyThe Public Land Survey System, also called the Township and Range System or Public Land Rectangular Survey System, was created by the Land Ordinance of 1785 and called for the systematic partitioning of public lands in the United States. The land was divided into townships covering six square miles. Each township was then divided into 36 sections of one square mile. Sections were further divided into quarter sections of 160 acres. These in turn could be divided into quarters again, making lots of 40 acres. In order for this square grid of townships to extend across the United States, different meridians and baselines were created. See the Principle Meridians and Baselines map put up by the BLM to see how they were laid out. Southern California uses the San Bernadino Meridian. For more information see:
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