Geo 301 Midterm

A spatial representation of the environment

a graphic representation of the environment

direct experience

mentally orient yourself with respect to external environment

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

• convenient to use
• simplify our surroundings
• are credible documents
• have strong visual impact

focus on specific subject and be organized

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

• variable scale
• not on a map projection
• generalized?
• symbolized?

• 24,907 mi
• 40,075 km

• Parallels and Meridians
• use to locate features by their coordinates

• (latitude)
• equally spaced east - west

• North - South lines
• (longitude)

• 0 degrees to 90 degrees
• Spacing = 69.2 mi. per deg.

0 degrees to 180 degrees

Degrees + min/ 60 + seconds/3600

69.2 mi/ deg. * cosine (latitude)

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

180 degree meridian opposite from prime meridian

areas on earth bounded by equal increments of latitude and longitude

parallels are not spaced equally as on a sphere

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

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

1/x = map distance / ground distance

• 1. RF 1:24,000
• 2. Scale statement : one inch to 20,000 ft
• 3. Scale bar

• Zoomed in
• Smaller RF

• Zoomed out
• Larger RF

• 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

• 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

• 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

geometrical transformation of the earths spherical or ellipsoidal

• continuity
• correspondence relations
• distance
• area
• direction
• shape
• completeness

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

• Planar
• Cylindrical
• Conical

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

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

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

projections that preserve global directions

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

preservation of distance on a map projection

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

• Azimuthal
• Conformal
• Equidistance
• Equal Area

• mercator cylindrical conformal
• transverse mercator
• lambert conformal
• alberts equal area

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

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

• 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

• 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

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

showed 3rd world countries more fairly

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

84 degrees N to 0 degrees to 80 degrees S latitude

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

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

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

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

• Township and Range System
• Prior to settlement and required all grants be recorded
• 1-36
• 37< = Donation Land Claims
• Prinicpal Meridians and Base Lines

• impose methods on the map from the outside
• judgements, calcualtions, methods

distortions in a map

• use scale bar
• use latitude as a scale bar
• use map rulers
• use mechanical measuring devices

• 1 liner feature
• 2 liner features
• Prominent objects

angular difference between true and magnetic

true and magnetic north poles are aligned

early mariners, use winds to find their way

GPS correction data for precision aircraft positioning

Global Positioning System