Geo 301 Midterm
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Map
A spatial representation of the environment

Cartographic map
a graphic representation of the environment

Egocentric
direct experience

Geocentric
mentally orient yourself with respect to external environment

Map Characterisitcs
 (Mapness)
 vertical or oblique view of the environment
 drawn to scale
 drawn on a map projection
 generalized and symbolized representation

what makes maps popular?
 convenient to use
 simplify our surroundings
 are credible documents
 have strong visual impact

Thematic maps
focus on specific subject and be organized

Map Use
process of obtaining useful information from one or more maps to help you understand the environment and improve mental map

How does an image differ from a cartographic map?
 variable scale
 not on a map projection
 generalized?
 symbolized?


Graticule
 Parallels and Meridians
 use to locate features by their coordinates

Parallels
 (latitude)
 equally spaced east  west

Meridians
 North  South lines
 (longitude)

Numerical range of Latitude
 0 degrees to 90 degrees
 Spacing = 69.2 mi. per deg.

Numerical range of Longitude
0 degrees to 180 degrees

Degrees, Minutes, Secs to Decimal Degrees
Degrees + min/ 60 + seconds/3600

Spacing of meridians
69.2 mi/ deg. * cosine (latitude)

Great Circle
largest possible circle that could be drawn on the surface of the spherical earth

Antipodal meridian
180 degree meridian opposite from prime meridian

Quadrilaterals
areas on earth bounded by equal increments of latitude and longitude

Oblate Ellipsoide
parallels are not spaced equally as on a sphere

Geodetic latitude
 angle made by a line perpendicular to ellipsoid surface at the parallel and equator line
 is on large scale maps

Geoid
 surface where gravity is the same as at mean sea level (MSL)
 elevation measure by geoid, but GPS uses ellipsoid

Representative Fraction (RF)
1/x = map distance / ground distance

Ways of specifying scale
 1. RF 1:24,000
 2. Scale statement : one inch to 20,000 ft
 3. Scale bar



Calculating RF from a known terrestrial feature:
1 mi wide section of land = 1.01 in on map
 1/x = 1.01in / (1 mi. * 63,360 in /mi)
 = 1.01 in / 63,360 in
 x = 63,360 in / 1.01 = 62,500
 1:62,500

Calculate RF from reference material:
1:62,500 distance between roads 5.69 in and 7.42 in on your map
 1/62,500 = 5.69 in
 1/x 7.42 in
 x = 62,500 = 5.69 in /7.42 in = 47,900
 1:47,900

Calculating RF from spacing of parallels and meridians:
2 parallels separated by 30 minutes of lat to be 4.37 inches apart on map
 30 minutes of lat = .5 deg *69.2 mi/deg = 34.6 mi
 1/x = 4.37 in /34.6 mi
 = 4.37 in / (34.6 mi *63,369 in/mi)
 x = 34.6 mi *63,360 in/mi / 4.37 mi
 1:502,000

Map Projection
geometrical transformation of the earths spherical or ellipsoidal

Geometric Distortions on Maps
 continuity
 correspondence relations
 distance
 area
 direction
 shape
 completeness

Geoid
project earths irregular surface topography onto a more regular imaginary surface.

Three map projection families

Tangent  Case
Projection surface may either touch the globe at a point (point of tangency) or along a line (line of tangency)

Secant  Case
planar projection surface intersects the globe along a small  circle line of tangency

Azimuthal Projections
 (planar projections)
 projecting onto a plane tangent to the globe at a point

Azimuthal
projections that preserve global directions

Conformal
 angles on the globe are preserved on the map
 "correct form or shape"

Equidistance
preservation of distance on a map projection

Aspect
Location of the point or line(s) of tangency on the generating globe

What are the 4 map projection properties?
 Azimuthal
 Conformal
 Equidistance
 Equal Area

Four map projections on geometric distortions
 mercator cylindrical conformal
 transverse mercator
 lambert conformal
 alberts equal area

Orthographic
 projection is how the earth would appear if view from a distant planet
 all rays of light are infinite and parallel

Stereographic
projecting a light source from the antipodal point on the generating globe to the point of tangency

Gnomonic
 earliest map projections, first used for star maps by Greek scholar Thales of Miletus in 6th century B.C.
 all great circles on the earth are shown as straight lines

Azimuthal equidistant
 projection in its polar aspect has the distinctive appearance of a dart board  equally spaced parallels and straight line meridians radiating outward from the pole
 all straight lines drawn from point of tangency are great circle routes

Rhumb Lines
all lines of constant compass direction; are straight lines on mercator map

Peters Projection world map
showed 3rd world countries more fairly

Transverse Mercator
Rhumb lines are not straight lines; north  south of earth are projected with no local shape distortion and little distortion in area

Universal Transverse Mercator (UTM)
84 degrees N to 0 degrees to 80 degrees S latitude

Cartesian Coordinates
square grid on the map with divisions left to right on horizontal X axis and divisions bottom to top labeled on a vertical Y axis

State Plane Coordinates
created in 1930's by land surveying in US define property boundries

Metes and Bounds System
 Property Boundry
 Legal property description tied to earth features and remained useful as long as neighbors agreed with place names and accepted the boundries

French Long Lots
 Along rivers or lakes = chief source of transportation and communication for French
 waterfront as parallels lines, creating narrow ribbon farms or long lots

US Public Land Survey (USPLSS)
 Township and Range System
 Prior to settlement and required all grants be recorded
 136
 37< = Donation Land Claims
 Prinicpal Meridians and Base Lines

External Errors
 impose methods on the map from the outside
 judgements, calcualtions, methods

Internal Errors
distortions in a map

Physical measurement for distance
 use scale bar
 use latitude as a scale bar
 use map rulers
 use mechanical measuring devices

Orienting by Inspection
 1 liner feature
 2 liner features
 Prominent objects

Magnetic Declination
angular difference between true and magnetic

Agonic Line
true and magnetic north poles are aligned

Compass Points
early mariners, use winds to find their way

Wide Area Augmentation System (WAAS)
GPS correction data for precision aircraft positioning

GPS
Global Positioning System