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GIS Roots in Cartography


Understanding the way maps are encoded to be used in GIS requires knowledge of cartography. ... A GIS is scaleless because maps can be enlarged and reduced and ... – PowerPoint PPT presentation

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Title: GIS Roots in Cartography

GIS Roots in Cartography
  • Front Range Community College
  • GIS 101 Week 2
  • Damon D. Judd

Basic Cartographic Principles
  • Principles of Geodesy and Cartography
  • Measuring the Earth
  • Characteristics of Geographic Data
  • Map Scale Map Projections
  • Coordinate Systems
  • Maps and Attributes

Cartography and GIS
  • Understanding the way maps are encoded to be used
    in GIS requires knowledge of cartography.
  • Cartography is the science that deals with the
    construction, use, and principles behind maps.
  • A map is a depiction of all or part of the earth
    or other geographic phenomenon as a set of
    symbols and at a scale whose representative
    fraction is less than one to one.

  • The art, science, and craft of mapmaking.
  • Cartography is the science that deals with the
    construction, use, and principles behind maps.

Quote from Edwin Raisz
GIS Data Linked with Maps
  • a set of measurements, text, or other values for
    at least one attribute and at least one record.

  • a collection of data organized in a systematic
    way to provide access on demand.

  • data logically stored together at one location on
    the storage mechanism of a computer (e.g. on

  • a set of values for all attributes for a given
    feature or object stored in a database.
    Equivalent to a row of a data table.

  • the content of an attribute for a single record
    within a database. Values can be text, numeric,
    or codes.

  • A numerical entry that reflects a measurement or
    value for a feature.
  • Attributes can be labels, categories, or numbers
    they can be dates, standardized values, or fields
    or other measure items.
  • An item for which data are collected and
    organized. A column in a table or data file.

  • Attributes
  • Parcel number
  • Owner
  • Address
  • Value
  • Graphic (map) feature
  • Parcels

Mapping the Earth
  • How big is the earth?
  • What is a map?
  • How is map data stored in a computer for use with
    a GIS?
  • Why is the way we store digital data about the
    Earth important?

  • The science which deals with the determination of
    the size and shape of the Earth, and which
    derives three-dimensional positions for points
    above, on, and below the surface of the Earth.

How Big is the Earth?
  • Nearly 25,000 miles (40 million meters) in
  • The earth can be modeled as a
  • sphere
  • oblate ellipsoid
  • geoid

The Geoid
  • The geoid is the surface of reference for
    astronomic observations and for geodetic
  • The geoid is a figure that adjusts the best
    ellipsoid and the variation of gravity locally.
  • It is the most accurate, but is not typically
    used for GIS and cartography.

Geoid Measurements
The Spheroid and Ellipsoid
Oblate Ellipsoid
  • An oblate ellipsoid is an ellipse rotated in
    three dimensions about its shorter axis.
  • The earth's ellipsoid is only 1/297 off from a
  • Many ellipsoids have been measured, and maps
    based on each. Examples are WGS84 and GRS80.

Earth Models and Datums
The Datum
  • An ellipsoid gives the base elevation for
    mapping, called a datum.
  • Relative to geographic area being projected
  • Examples are NAD27 and NAD83.

NAD 27
  • North American Datum of 1927.
  • Used on older mapping. Datum origin centered on
    Meades Ranch, Kansas.
  • Many older maps still use NAD 27.

NAD 83
  • North American Datum of 1983
  • The horizontal control datum for the United
    States, Canada, Mexico, and Central America.
  • Based on a geocentric origin and Geodetic
    Reference System 1980 (GRS80).
  • The basis for all maps created since 1986 - a
    small percentage of the total.

World Geodetic System 1984 (WGS84)
  • Revised in 1984 from GRS80.
  • A unified world datum based on a combination of
    all available astrogeodetic, gravimetric, and
    satellite tracking observations.
  • The reference ellipsoid is revised as new
    measurement techniques change the currently
    accepted values.
  • A common datum used in GPS receivers.

Definition Map
  • A representation usually on a flat surface of
    the whole or part of an area.
  • The graphic representation of spatial
    relationships and spatial forms.
  • A graphic depiction of all or part of a
    geographic realm in which the real-world features
    have been replaced by symbols in their correct
    spatial location at a reduced scale.

The Scope of Cartography
  • The Cartographer and the Map User.
  • Ask yourself Who is the audience of the map
  • The cartographic sequence is the cycle of events
    that occur in map making and map reading.

The Cartographic Sequence
  • Collecting and selecting the data for mapping.
  • Manipulating and generalizing the data, designing
    and constructing the map.
  • Reading or viewing the map.
  • Responding to or interpreting the data.

Functional Types of Maps
  • General Portray the spatial association of
    selected geographical phenomena.
  • Thematic Concentrate on the spatial variations
    of the form of a single attribute or the
    relationship among several attributes.
  • Charts Serve the needs of navigators.

General Maps
  • Road/Planimetric
  • Topographic
  • Atlas
  • Cadastral/Property Map
  • Facility/Engineering
  • Site Plan/Map
  • Orthophoto Map
  • Lunar/Planetary

Thematic Maps
  • Choropleth Portrayal of a statistical surface
    by areal symbols.
  • Dot maps
  • Proportional symbol maps
  • Isometric (e.g. contour) maps

  • Navigation Charts
  • Aeronautical
  • Nautical
  • Bathymetric

Map Design Components
  • Every map should have
  • Title
  • Legend
  • Map scale
  • North arrow
  • Credits
  • Date

Categories of Map Features
  • Consider classifying or organizing map features
    by type.
  • Examples of map feature types
  • Planimetry
  • Topography
  • Cadastral
  • Areas/Political Boundaries
  • Facilities
  • Natural Resources

Cartographic Generalization
  • Simplification
  • Classification
  • Symbolization
  • Induction

  • The determination of the important
    characteristics of the data, the elimination of
    unwanted detail, and the retention and possible
    exaggeration of the important characteristics.

  • The ordering or scaling and grouping of data.

  • The graphic encoding of the scaled and/or grouped
    essential characteristics, comparative
    significance, and relative positions.

Induction (Interpolation)
  • The application of the logical process of
  • Creating a soil type map with sample point data.
  • Creating a DEM from elevation points.

Choosing the Wrong Map Type
  • Fairly common GIS error.
  • Often due to lack of knowledge about cartographic
  • Can still have perfect symbolization.
  • Possibility of misinformation (e.g. wrong data
  • Definite reduction in communication
  • Ref How to Make Maps Lie, by Mark Monmonier

Choosing Types
  • Check the data
  • Continuous
  • Discrete
  • Accuracy Precision
  • Reliability
  • Dimension (Point, Line, Area, Volume)
  • Scale of Measurment (NOIR)
  • GIS capability
  • May need to supplement GIS software

Continuity of Geographic Data
  • Discrete Distributions - Discrete data have known
    and definable boundaries.
  • distinct separation between objects
  • houses, city boundaries, roads
  • best represented using the vector data model
  • Continuous Distributions - do not have distinct
    boundaries like discrete geographic features.
  • no empty space
  • elevation, precipitation, reflectance
  • best represented with raster data model

Discrete Data
These data are discrete. There is empty space
between buildings and pipelines.
Continuous Data
This image depicts elevation bands. There is
elevation everywhere.
Classes of Geographic Phenomena - Dimensionality
  • Positional
  • point in space well, pole
  • Linear data
  • one-dimensional data road network
  • Area/Polygon data
  • two dimensional data city boundary
  • Volumetric data
  • 3-D volume of contaminated soil

Map Types Point Data
  • Reference (e.g. City on small-scale map)
  • Topographic
  • Dot
  • Picture Symbol
  • Graduated Symbol

Map Types Line Data
  • Network
  • Flow
  • Isopleth
  • Reference (e.g. County Boundary)

Map Types Area Data
  • Choropleth
  • Area qualitative
  • Stepped surface
  • Hypsometric (e.g. elevation ranges)
  • Dasymetric
  • Reference

Map Types Volume Data
  • Gridded fishnet
  • Realistic perspective
  • Hill-shaded
  • Image map
  • Subsurface volumetrics

Data Scaling
  • Nominal (Name of a place)
  • Ordinal (Small, medium, large town)
  • Interval (Arbitrary zero e.g. Sea Level)
  • Ratio (Absolute zero e.g. population, densities)

  • Distinguish between objects based on their
    intrinsic character qualitative differentiation.
  • Root of word nominal is nom, or name.
  • point wholesale vs. retail establishment
  • line river vs. road
  • area land use class, e.g., urban vs. rural

  • Involves nominal classification, but also
    differentiates within a class of data involves
    rank of objects, but NOT a measurement.
  • point classification of cities into small,
    medium, and large
  • line large river vs. small river vs. creek, or
    major highway vs. secondary roads
  • area crop yield high, medium, low

  • Adds information of distance between ranks to the
    description of class and rank uses standard
    units and then expresses the difference in terms
    of standard unit. Interval can be an arbitrary
    scale Ratio uses an absolute value from a datum.
  • point spot elevation or precipitation values
  • line contour lines
  • area average temperature of a state number of
    species within an eco-region

Making Maps of the Earth
  • Map Scale - The ratio of distance measured on a
    map to the corresponding distance on the ground.
  • Map Projections - A mathematical model used to
    transform positions on the curved surface of the
    earth onto a flat map surface.
  • Coordinate Systems - a standardized method for
    assigning codes to locations so that locations
    can be found using the codes alone.

Map Scale
  • Map scale is based on the representative
    fraction, the ratio of a distance on the map to
    the same distance on the ground.
  • A GIS is scaleless because maps can be enlarged
    and reduced and plotted at many scales other than
    that of the original data.
  • To compare or edge-match maps in a GIS, both maps
    MUST be at the same scale and have the same map

Scale of a baseball earth
  • Baseball circumference 226 mm
  • Earth circumference approx 40 million meters
  • RF is 1177 million

Small vs. Large Scale Maps
  • Small scale
  • Covers large area
  • Less detail
  • Large scale
  • Covers small area
  • Greater detail

Presentations of Map Scale
  • Bar scale
  • Example 0__________100mi.
  • Verbal or Engineering scale
  • Example 1100
  • Representative Fraction
  • Example 124,000

Map Projections
  • A mathematical model used to transform positions
    of the spherical or ellipsoidal earth onto a flat
    map surface.
  • The map projection can be onto a flat surface or
    a surface that can be made flat by cutting, such
    as a cylinder or a cone.
  • If the globe, after scaling, cuts the surface,
    the projection is called secant. Lines where the
    cuts take place or where the surface touches the
    globe have no projection distortion.

Properties of Map Projections
  • Projections can be based on axes parallel to the
    earth's rotation axis (equatorial), at 90 degrees
    to it (transverse), or at any other angle
  • A projection that preserves the shape of features
    across the map is called conformal.
  • A projection that preserves the area of a feature
    across the map is called equal area or
  • No flat map can be both equivalent and conformal!

Mercator Projection
  • Used for navigation or maps of equatorial regions
  • Distance only true along equator
  • Area distortion increases away from equator
  • Conformal in angles and shapes in small areas
  • Latitude longitude straight lines

Albers Equal Area
  • Conic
  • Used by USGS for conterminous US
  • All areas proportional to same area on the Earth
  • Directions are reasonably accurate in limited
  • Distances true on standard parallels

Lambert Conformal Conic
  • Used by USGS for State Base Map Series
  • Looks like Albers Equal Area
  • Distance true along standard parallels
  • Directions reasonably accurate
  • Shapes essentially true

Azimuthal Equidistant
  • Used by USGS in National Atlas of the United
    States of America
  • Distances and directions true to all points from
    center point of projection
  • Distortion increases away from center point

Map Projection References
  • Pearson, Frederick. Map Projections Theory and
    Applications. Boca Raton CRC Press, Inc., 1990
  • Robinson, Arthur et. al. Elements of
    Cartography. New York John Wiley Sons, Inc.,
  • Snyder, John P. Map Projections - A Working
    Manual. U.S. Geological Survey Professional
    Paper 1395. Washington United States
    Government Printing Office, 1987.

Coordinate Systems - definition
  • A coordinate system is a standardized method for
    assigning codes to locations so that locations
    can be found using the codes alone.
  • Standardized coordinate systems use absolute
  • In a Cartesian coordinate system, the x-direction
    value is the easting and the y-direction value is
    the northing. Most systems make both values

Coordinate Systems
  • Geographical Coordinates or Spherical Coordinates
  • Example Latitude/Longitude
  • Plane Rectangular or Cartesian Coordinates
  • Universal Transverse Mercator (UTM)
  • State Plane Coordinate System

  • Equator 0
  • North Pole 90
  • South Pole 90
  • Prime Meridian 0
  • Intl Date Line 180
  • Latitude Parallels
  • Longitude Meridians
  • In GIS software we use negative values in West
    and South quadrants.

Coordinate Systems for the US
  • Some standard coordinate systems used in the
    United States are
  • geographic coordinates
  • Universal Transverse Mercator (UTM)
  • State Plane
  • To compare or edge-match maps in a GIS, both maps
    MUST be in the same coordinate system.

X and Y Confusion
  • Question Which values represent the X and Y
    coordinates in latitude and longitude?

  • Expressed in Degrees, Minutes, Seconds (DMS)
  • or
  • Expressed in Decimal Degrees (DD)
  • For example, 40 30 can be expressed as 40.5

Universal Transverse Mercator (UTM) Coordinates
  • A common rectangular (Cartesian) coordinate
    system based on projection of a location on the
    earth onto a cylindrical surface.
  • Coordinates are usually expressed in meters north
    (northings) and meters east (eastings) from
    reference axes that define a given zone.

UTM Zones in theContinental U.S.
  • Approximate Latitude / Longitude
  • 40 degrees north latitude
  • 105 degrees west longitude (-105)
  • UTM Zone 13
  • Easting 500,000m E
  • Northing 4,000,000m N

State Plane Coordinate System
  • A grid system that was developed by the National
    Geodetic Survey for each state.
  • The earths surface, reduced to sea level, is
    projected onto a series of planar surfaces.
  • A Lambert conical or Transverse Mercator
    projection is used, depending on the states
  • A state can have more than one zone, and each
    zone has an origin for a grid system.

State Plane Coordinates (cont.)
  • The location of points is expressed in terms of
    coordinates x and y from this origin.
  • Based on Transverse Mercator or Lamberts Conic
  • Feet (can be translated to meters)
  • Large states broken into zones
  • Colorado North, Central, South

1997 Colorado Revised Statutes
  • 38-52-101. Colorado coordinate system zones
  • (1) The systems of plane coordinates which have
    been established by the national ocean
    service/national geodetic survey (formerly the
    United States coast and geodetic survey) or its
    successors for defining and stating the
    geographic positions or locations of points on
    the surface of the earth within the state of
    Colorado are, on and after July 1, 1988, to be
    known and designated as the Colorado coordinate
    system of 1927 and the Colorado coordinate system
    of 1983. (2) For the purpose of the use of these
    systems, the state is divided into a north zone,
    a central zone, and a south zone. (3) The area
    now included in the following counties shall
    constitute the north zone Moffat, Routt,
    Jackson, Larimer, Weld, Logan, Sedgwick, Rio
    Blanco, Grand, Boulder, Gilpin, Adams, Morgan,
    Washington, Phillips, and Yuma. (4) The area now
    included in the following counties shall
    constitute the central zone Garfield, Eagle,
    Summit, Clear Creek, Jefferson, Denver, Arapahoe,
    Lincoln, Kit Carson, Mesa, Delta, Pitkin,
    Gunnison, Lake, Chaffee, Park, Fremont, Teller,
    Douglas, El Paso, Elbert, and Cheyenne. (5) The
    area now included in the following counties shall
    constitute the south zone Montrose, Ouray,
    Hinsdale, Saguache, Custer, Pueblo, Crowley,
    Kiowa, San Miguel, San Juan, Mineral, Rio Grande,
    Alamosa, Huerfano, Otero, Bent, Prowers, Dolores,
    Montezuma, La Plata, Archuleta, Conejos,
    Costilla, Las Animas, and Baca.

Colorado State Plane Zones
University of Denver GIS Lab
  • Lat/Long (DMS)
  • 39 40 28.29738 N.
  • 104 57 47.70038 W.
  • State Plane Coordinates
  • 2,151,089 feet East
  • 671,008 feet North
  • UTM
  • 503,151 meters East,
  • 4,391,634 meters North

GIS Capabilities
  • A GIS package should be able to move between
  • map projections,
  • coordinate systems,
  • datums, and
  • ellipsoids.

Coordinate Transformation
  • The ability to translate or transform different
    coordinate systems into the coordinate system of
  • Provides capability to merge data from disparate
    sources into common coordinate system framework.

  • GIS has its roots in cartography. The ability to
    make maps on the computer has been around since
    the 1950s.
  • With the linking of a database to a map, we truly
    have a Geographic Information System.
  • Projections and coordinate systems are a way of
    organizing data describing a spherical
    (elliptical) planet onto a flat surface.
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