Key Terms Map: a flat representation of a globe Cartography - the art and science of mapmaking
SCALE Scale: the relationship between units on the map and actual distance on the ground Verbal Scale: one inch equals one mile Linear Scale: |---------|---------|----------| –or Graphic Scale Representative Fraction: 1:63,360
Latitude & Distance Earth’s Circumference 24,840 miles 24,840 divided by 360 degrees of a circle One degree equals 69 miles One degree can be divided into 60 parts or minutes 69 miles divided by 60 equals 1.15 miles Therefore one minute equals 1.15 miles One minute is a nautical mile (1.15 miles)
Latitude & Distance One minute can be further divided into 60 seconds One minute or 1.15 miles divided by 60 equals 102 feet Therefore one second equals 102 feet WHAT IS THE DISTANCE SHOWN ON A 15 MINUTE MAP?
Map Projections Projection: The system used to transfer locations from Earth’s surface to a flat map. –A projection of an image onto another surface either a cylinder, a flat plane or a cone –3 basic types of projections –cylindrical projection –planular projection (also known as azimuthal) –conical projection
The Mercator projection has straight meridians and parallels that intersect at right angles. Scale is true at the equator or at two standard parallels equidistant from the equator. The projection is often used for marine navigation because all straight lines on the map are lines of constant azimuth.
CYLINDRICAL PROJECTION used by navigators to show direction Meridians run north & south Parallels run east & west Distortion on a Mercator map increases at an increasing rate as one moves toward higher latitudes.
Robinson projection. Robinson projection. This projection was developed to show the entire Earth with less distortion of area. However, this feature requires a tradeoff in terms of inaccurate map direction and distance.
This projection is common in maps that require somewhat accurate representation of area. This map projection was originally developed for Rand McNally and Company in 1961.
To calculate a percent slope Divide the change elevation (ft) by the distance covered ---------|--------- change elevation (ft) distance covered = X100 Average slope
Township and Range System The Township and Range system, sometimes called the Public Lands Survey System, was developed to help parcel out western lands as the country expanded. The system takes many western states and divides them up using a base line and a principal meridian. This system divides the land up into townships and ranges that are 36 square miles each.
Terms: Base Line: The horizontal line where the survey began. Meridian: The vertical line where the survey began. Washington and Oregon are on the Willamette Meridian. Range: The measure of township squares east or west of the meridian. Section: A square mile numbered between 1 and 36 containing 640 acres. Township: A six by six mile square containing 23,040 acres divided into 36 sections. Also used for the measure of township squares north or south of the base line.
In the diagram, the square with the X in it would be defined as township 2 south (T.2S), range 3 east (R.3E). Each township and range is then subdivided into 36 sections. Each section is one mile square. Individual sections are then subdivided into half sections and quarter sections and so on. In the map below you can see sections 23, 24, 26 and 25 of T.22N, R.7E. Township and Range System
Township & Range Public Land Survey System A rectangular grid system adjusted to the geographic grid East west lines are surveyed and coincide with parallels of latitude –prominent parallel is known as the base line Vertical divisions are called ranges –prominent meridians are called principal meridians
Basic unit is the township –Approximately 6 miles square –36 sections of one square mile –Plus allowances for road access Sections –640 acres, more or less –4 quarters, 160 acres, more or less –16 legal subdivisions (lsds), 40 acres Township & Range Public Land Survey System
Layout of Townships Began along 49 th parallel of Latitude 10 Miles W of junction of Red and Pembina Rivers (Longitude 97 degrees, 27 minutes West) E-W rows called Townships N-S columns called Ranges