GE 30 - LE 1.

• Cartography


  The art, science and technology of making maps together with their study as scientific documents and as works of art
• Map


  An abstraction of reality for analyzing, storing, and communicating information about the locations, attributes, and inter-relationship of physical and social phenomena that are distributed over the earth's surface
• Characteristics of Maps


  • Drawn to Scale - defined as dimensional relationship between reality and map
  • Emphasize selected features - Large Symbols, Heavy Lines, Pointing Arrows, Colors
  • Symbolized - uses different symbologies for various attributes of the map
  • Lettered, titled and labelled - title or map content, legend, data, source
  • Have orientation- Direction of North
• Purpose of Maps

  • Navigation
  • Visualization
  • Measurement
• Application of Maps


  • Agriculture
  • Economic Planning
  • Education and Research
  • Environment and Natural Resources
  • Finance
  • Health
  • Land Management
  • Legislative
  • LGU Development
  • National Defense
  • Private Land Development
  • Public Works
  • Social Welfare and Development
  • Justice
  • Tourism
  • Transportation and Communication
• Classification of Maps by Scale


  • Small Scale (1:500,000 or more) - national planning
  • Medium Scale (Between 1:50,000 & 1:500,000) - regional planning
  • Large Scale (1:50,000 or less) - provincial, metropolitan - municapality/ city, land-use planning
• Classification of Maps by Function


  • General maps - reference maps, base maps
  • Charts
  • Analytical maps
  • Thematic maps - overlay maps
• Classification of Maps by Subject Matter


  • Cadastral map
  • As-built map/Plans
  • Geologic map
  • Climatic map
  • Soil map
  • Economic map
  • Population map
  • Transportation map
• Other Types of Maps

  • Line maps
  • Photo maps (standard, rectified, mosaic)
  • Computer generated maps
  • Location/vicinity map
  • Tube map
  • Flow map
  • Cartogram
• Advantages of Maps

  • More objective and efficient than verbal descriptions
  • Useful source of data and give historical perspective
  • Useful in engineering design and construction
  • Can lead us to insights, discoveries and new ways of understanding
• Limitations of Maps

  • No single map can show all the features of a landscape (simplification of reality)
  • Maps are related to a specific use
  • Maps can be misleading, because of the selection and generalization of data represented on the map
• Geodesy


  Science of Earth's measurement: shape, orientation, and gravity
• Datum


  Defines the position of the ellipsoid relative to the center of the Earth and provides a frame of reference for measuring locations on the surface of the Earth
• Coordinate Systems


  • Geographic/global coordinate system (Latitude/Longitude)
  • Cartesian/planar coordinate system (Northing/Easting/Elevation)
• Latitude (φ)


  Angular distance from equator; along Y axis
• Longitude (λ)


  Angular distance from standard meridian; along X axis
• Cartesian/planar coordinate system


  • Northing/Easting/Elevation
  • Also called Cartesian coordinate geometry
  • A system of intersecting perpendicular lines on a plane with two principal axes (x - and y –axes)
  • The position of any point P can be specified by the values of x and y and plotting its location with respect to the Cartesian plane
• Datum


  • While a spheroid approximates the shape of the earth, a datum defines the position of the ellipsoid relative to the center of the Earth
  • Provides a frame of reference for measuring locations on the surface of the Earth
  • Chosen to align a spheroid to closely fit the Earth's surface in a particular area
  • It is important to ensure that the datum of a dataset matches with the datum setting of your workspace/mapping environment and with other data sets being used
• Coordinate Reference Systems (CRS)


  The combination of a coordinate system and a datum
• Philippine Reference Systems
• Map Projections


  • A systematic transformation of the latitudes and longitudes of locations on the surface of a sphere or an ellipsoid into locations on a plane
  • Necessary for creating maps
  • Maps are models and are generalized representations of reality
  • All map projections distort the surface, each projection distorts differently
  • The larger the land surface represented the more curvature of the Earth encompassed, and the greater the necessity for projections to construct flat map
  • Function is to define how positions on the Earth's curved surface are transformed into a flat map surface
  • Geographic coordinates (Φ,λ) to Cartesian coordinates (x,y)
• Developable Surfaces


  • The Earth cannot be pulled or cut apart to lie flat the way a map does. Neither the Earth nor any of its three-dimensional representations (such as the geoid, ellipsoid, sphere, or globe) are developable surfaces
  • A developable surface has the property that it can be obtainable by transformation from a plane. It can be flattened without distortion
  • Geometric forms used: plane, the cylinder, and the cone. These give rise to four overall families of map projections: azimuthal, cylindrical, conic, and mathematical
  • Mathematical projections (those that cannot be developed by projective geometry) are in some cartographers' taxonomies simply classified into the geometric families based on their appearances. A few projections bear striking resemblance to the developable ones but are different enough to be classed as pseudocylindrical, pseudoconic, and pseudoazimuthal
• Aspect

  • The position of the projected graticule relative to the ordinary position of the geographic grid on the Earth
  • It can be visualized as the position of the developable geometric surface to the reference globe
  • It may be normal (such that the surface's axis of symmetry coincides with the Earth's axis), transverse (at right angles to the Earth's axis) or oblique (any angle in between)
• Viewpoint

  Location of the "light source" of projection
• Intersection

  • Refer to the point/circle of tangency: tangent or secant
  • The location of highest accuracy/less distortion is at the point/circle of tangency
• Distortions from map projections

  • It is impossible to render the spherical surface of the reference globe as a flat map without distortion error caused by tearing, shearing, or compression of the surface
  • The designer's task is to select the most appropriate projection so that there is a measure of control over the unwanted error
• Tissot's Indicatrix


  A mathematical contrivance used in cartography to characterize local distortions in map projections
• Properties of Map Projections

  • Conformal/true-shape/orthomorphic
  • Equal-area/equivalent/equiareal/authalic
  • Equidistant
  • Azimuthal/zenithal/true-direction
• On an ideal map, X = fX(ɸ, λ) and Y = fY(ɸ, λ) must satisfy the following conditions:
• A map projection can only satisfy some of these properties
• AuthaGraph


  • From authalic and –graph
  • May be the most accurate map projection created to date
• UTM - Universal Transverse Mercator


  • Secant projection
  • Cylindrical surface in transverse aspect
  • Two standard meridians
  • Scale at each zone's central meridian is 0.9996 and at most 1.0004 at the edge of the zone
  • Parallels and meridians are curved, except for the central meridians and equator
  • Map is divided into 60 zones, each 6° wide
  • Problematic for areas at high latitudes and places that are in two zones
  • Commonly used for military applications and for mapping at a global or national coverage
• Factors affecting choice of suitable map projections

  • Scale
  • Parameters (Radius of the sphere or equatorial and polar radius of the reference ellipsoid, Geodetic datum, Origin of the coordinate system, False easting and northings, Central meridian, standard parallels, or center of projection, Scale factor at the central meridian or standard parallels)
  • Size, shape and geographical location of the area
• Traditional Approach (La Putt, 1986)

  • Use cylindrical projection for areas in the tropics
  • Use conical projection for areas in the temperate latitudes
  • Use azimuthal projection for areas in the polar region
• Scale


  • The ratio of a distance on the map to the corresponding distance on the ground measured in the same unit
  • Relates to the size of the area being studied and determines the level of precision and generalization applied in the study
  • An elusive thing because, by the very nature of the necessary transformation from the sphere to the plane, the scale of a map must vary from place to place and will even vary in different directions at a point
  • Scales are relative to the amount of detail required in the map and the required information; thus, scale dictates precision and generalization of the area
  • Transformation algorithms tend to add distortions on the planar figure which varies the scale at different areas and at different direction; it is an inherent limitation of map projections; thus, projections are chosen depending on the area or information that is needed to be represented
  • Maps are necessarily smaller than the areas mapped
  • To be usable maps must state the ratio or proportion between comparable measurements
• Forms of scale


  • Equivalent scale or verbal scale/statement
  • Representative fraction (RF) or scale ratio
  • Graphic or bar scale
  • Areal scale
• Types of scale


  • Large Scale (1:50,000 or less)
  • Medium Scale (between 1:50,000 and 1:500,000)
  • Small Scale (1:500,000 or more)
• Choice of map scale

  • Purpose of survey
  • Clarity with which the features can be shown
  • Cost
  • Size of map sheet
  • Physical factors or choice of terrain
• Limitations due to scale

  • The information that can be included
  • The manner that the information can be presented
• Geodesy


  Science of Earth measurement