5Latitude & Distance Earth’s Circumference 24,840 miles 24,840 divided by 360 degrees of a circleOne degree equals 69 milesOne degree can be divided into 60 parts or minutes69 miles divided by 60 equals 1.15 milesTherefore one minute equals 1.15 milesOne minute is a nautical mile (1.15 miles)
6Latitude & Distance One minute can be further divided into 60 seconds One minute or 1.15 miles divided by 60 equals 102 feetTherefore one second equals 102 feetWHAT IS THE DISTANCE SHOWN ON A 15 MINUTE MAP?
7Map ProjectionsProjection: The system used to transfer locations from Earth’s surface to a flat map.A projection of an image onto another surfaceeither a cylinder, a flat plane or a cone3 basic types of projectionscylindrical projectionplanular projection (also known as azimuthal)conical projection
8The 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.
9CYLINDRICAL PROJECTION used by navigators to show directionMeridians run north & southParallels run east & westDistortion on a Mercator map increases at an increasing rate as one moves toward higher latitudes.
16Robinson 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.
17This 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.
24X 100 = To calculate a percent slope Divide the change elevation (ft) by the distance coveredchange elevation (ft)|X100=Average slopedistance covered
25Township 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.
26Terms: 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.
27Township and Range System 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.
28Township & Range Public Land Survey System A rectangular grid system adjusted to the geographic gridEast west lines are surveyed and coincide with parallels of latitudeprominent parallel is known as the base lineVertical divisions are called rangesprominent meridians are called principal meridians
29Township & Range Public Land Survey System Basic unit is the townshipApproximately 6 miles square36 sections of one square milePlus allowances for road accessSections640 acres, more or less4 quarters, 160 acres, more or less16 legal subdivisions (lsds), 40 acres