mapping your data 1
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Mapping Your Data
Christopher Martincsmartin@buffalo.edu
Data ModelsData Models
Two primary data models used when making mapsRaster DataVector Data
Two primary data models used when making mapsRaster DataVector Data
Raster DataRaster Data
Consists of discrete cells (think graph paper) Each cell has a discrete valueOccur in rows and columns
ExamplesImages (all image types)DEM
Consists of discrete cells (think graph paper) Each cell has a discrete valueOccur in rows and columns
ExamplesImages (all image types)DEM
Vector DataVector Data
Each position is represented by coordinates
Coordinates are connected to form lines or polygons
Points, lines and polygons are then used to represent geographic features
ExamplesShapefile
Each position is represented by coordinates
Coordinates are connected to form lines or polygons
Points, lines and polygons are then used to represent geographic features
ExamplesShapefile
Points, Lines, PolygonsPoints, Lines, Polygons
Data SourcesData Sources
US Census BureauNot just population data Generalized Boundary Data
ESRITIGER/LINENED DataFEMA Q3 Flood Data
USGSSEAMLESS Distribution
US Census BureauNot just population data Generalized Boundary Data
ESRITIGER/LINENED DataFEMA Q3 Flood Data
USGSSEAMLESS Distribution
Data Sources (cont’d)Data Sources (cont’d)
NYS GIS Clearing HouseMembership requiredWide variety of data
CUGIRNYS and National dataFree, huge variety
CIGARWorldwide Elevation Data
Columbia University EDSElectronic Data Service
NYS GIS Clearing HouseMembership requiredWide variety of data
CUGIRNYS and National dataFree, huge variety
CIGARWorldwide Elevation Data
Columbia University EDSElectronic Data Service
Data Sources (cont’d)Data Sources (cont’d)
Geography NetworkAggregates data from different
providersOnline Map Server Available
Geography NetworkAggregates data from different
providersOnline Map Server Available
Data QualityData Quality
Meta DataData about the dataAll legitimate providers will provide
thisAvailable for download or online
viewing
Meta DataData about the dataAll legitimate providers will provide
thisAvailable for download or online
viewing
Map ScaleMap Scale
The ratio between the distance on the map, and the distance in real lifeALWAYS expressed in terms of 1Usually a ratio
E.g. 1:100000, 1:10000
Other scales are availableVisual scale is the second most common
The ratio between the distance on the map, and the distance in real lifeALWAYS expressed in terms of 1Usually a ratio
E.g. 1:100000, 1:10000
Other scales are availableVisual scale is the second most common
Coordinate SystemsCoordinate Systems
Two types of coordinate systems used in geographySpherical (Latitude and Longitude)
Typically not used in ArcGISAlways used in Google Earth
RectangularPredominantly used in Arc and GIS in generalUTM - Universal Transverse MercatorState PlaneOther countries have their own.
Two types of coordinate systems used in geographySpherical (Latitude and Longitude)
Typically not used in ArcGISAlways used in Google Earth
RectangularPredominantly used in Arc and GIS in generalUTM - Universal Transverse MercatorState PlaneOther countries have their own.
Spherical Coordinate System
Spherical Coordinate System
Based on meridians and parallelsLatitude (parallels)
Measured northward or southward from the equator to poles Ranging 0-900 north or south The measuring units are degrees, minutes, and seconds, 10 =
60’ and 1’=60” The length of one degree latitude is similar everywhere, ≈
111km/69miles Longitude (meridians)
Measured eastward or westward from the Prime Meridian at Greenwich, England to the International Date Line
Ranging 0-1800 east or west The measuring units are the same as Latitude Length of one degree longitude reduces toward poles
Based on meridians and parallelsLatitude (parallels)
Measured northward or southward from the equator to poles Ranging 0-900 north or south The measuring units are degrees, minutes, and seconds, 10 =
60’ and 1’=60” The length of one degree latitude is similar everywhere, ≈
111km/69miles Longitude (meridians)
Measured eastward or westward from the Prime Meridian at Greenwich, England to the International Date Line
Ranging 0-1800 east or west The measuring units are the same as Latitude Length of one degree longitude reduces toward poles
Rectangular Coordinate Systems
Rectangular Coordinate Systems
Convert the curved surface of the earth onto a flat surface
Standard cartesian coordinates, but different namesX is called “Easting”Y is called “northing”
Convert the curved surface of the earth onto a flat surface
Standard cartesian coordinates, but different namesX is called “Easting”Y is called “northing”
Universal Transverse Mercator
Universal Transverse Mercator
Based on the mercator map projectionDivides the world into 60 zones
Starts at 180 degrees longitudeEach zone is 6 degrees of longitude wideLabeled 1-60 going eastward
And 20 RowsLabeled C-X, skipping I and O
Intersection of Row and Zone is a QuadrangleUsually referred to as “quad”
Measurement unit is meters
Based on the mercator map projectionDivides the world into 60 zones
Starts at 180 degrees longitudeEach zone is 6 degrees of longitude wideLabeled 1-60 going eastward
And 20 RowsLabeled C-X, skipping I and O
Intersection of Row and Zone is a QuadrangleUsually referred to as “quad”
Measurement unit is meters
Universal Transverse Mercator
Universal Transverse Mercator
State PlaneState Plane
Used exclusively in the United StatesThe US is divided into 120 zones
Follow state and county linesEach state has its own map
projectionNorth to South states use MercatorEast to West states use Lambert
Conformal Conic
Used exclusively in the United StatesThe US is divided into 120 zones
Follow state and county linesEach state has its own map
projectionNorth to South states use MercatorEast to West states use Lambert
Conformal Conic
State PlaneState Plane
So What?So What?
Map ProjectionsMap Projections
A way to convert coordinates from spherical (earth) to flat (map)Projections define how to to
transform the spherical coordinates to flat ones
They are NOT map coordinatesClassified two ways
By the surface projected ontoBy what gets distorted
A way to convert coordinates from spherical (earth) to flat (map)Projections define how to to
transform the spherical coordinates to flat ones
They are NOT map coordinatesClassified two ways
By the surface projected ontoBy what gets distorted
SurfacesSurfaces
Developable SurfacesWhat kind of shape will we use?It has to be 2D, and we need to be able to
“unroll” itThe earth gets “wrapped” in the shape, and
the surface is transferred to the 2D shape
TypesCylindrical, Conic, Azimuthal
Developable SurfacesWhat kind of shape will we use?It has to be 2D, and we need to be able to
“unroll” itThe earth gets “wrapped” in the shape, and
the surface is transferred to the 2D shape
TypesCylindrical, Conic, Azimuthal
Cylindrical ProjectionsCylindrical Projections
MercatorTransverse Mercator
MercatorTransverse Mercator
Azimuthal ProjectionsAzimuthal Projections
Top down viewOr Bottom Up
Top down viewOr Bottom Up
Conic ProjectionsConic Projections
Used to focus on a particular continentLeast amount of
distortion for east-west direction
Used to focus on a particular continentLeast amount of
distortion for east-west direction
Distortion ProjectionsDistortion Projections
All maps distortIt’s inevitable
Projections can be grouped based on WHAT is distortedConformal - shapes are the sameEqual-Area - areas are the sameEquidistant - distances are the same*
All maps distortIt’s inevitable
Projections can be grouped based on WHAT is distortedConformal - shapes are the sameEqual-Area - areas are the sameEquidistant - distances are the same*
Projection ExampleProjection Example
Measuring DistortionMeasuring Distortion
Comparisons of Projections
Comparisons of Projections
Map Projection PosterMap Projection Poster
Map TypesMap Types
Thematic MapsNot reference maps
Four main typesChoropleth MapProportional MapIsarithmic Map (contour)Dot Map
Thematic MapsNot reference maps
Four main typesChoropleth MapProportional MapIsarithmic Map (contour)Dot Map
Choropleth MapChoropleth Map
Shaded AreasThe “color” of the shade varies based
on measurement of our variable
Shaded AreasThe “color” of the shade varies based
on measurement of our variable
Isarithmic MapIsarithmic Map
Also known as Contour MapsWe draw lines to
connect separate variables that have the same value
Also known as Contour MapsWe draw lines to
connect separate variables that have the same value
Proportional Symbol MapProportional Symbol Map
Uses symbolsThe size of the
symbol varies according to the variable
Uses symbolsThe size of the
symbol varies according to the variable
Dot Density MapDot Density Map
Uses dotsSize is uniform,
but the concentration represents changes in the variable
Uses dotsSize is uniform,
but the concentration represents changes in the variable
CartogramsCartograms
Are NOT mapsArea is not preservedArea of the geographic regions varies by
variable
Two primary typesArea
Area gets larger or smaller depending on the variable
DistanceNodes or places can be closer or farther depending on
realtive distance
Are NOT mapsArea is not preservedArea of the geographic regions varies by
variable
Two primary typesArea
Area gets larger or smaller depending on the variable
DistanceNodes or places can be closer or farther depending on
realtive distance
CartogramCartogram
File FormatsFile Formats
ShapefileA collection of points, lines and polygonsTabular data values assocated with each
DEMRaster data, each cell represents
elevationComes in different resolutions
ShapefileA collection of points, lines and polygonsTabular data values assocated with each
DEMRaster data, each cell represents
elevationComes in different resolutions
Getting to Know ArcGISGetting to Know ArcGIS
ArcMapYour main tool. Handles map layout,
projection, data classification, analysisArcCatalog
Asset management program. Maps drives of data for easy access, displays meta data, manages database connections
ArcViewOlder version of ArcMap.
ArcScene3D rendering
ArcMapYour main tool. Handles map layout,
projection, data classification, analysisArcCatalog
Asset management program. Maps drives of data for easy access, displays meta data, manages database connections
ArcViewOlder version of ArcMap.
ArcScene3D rendering
Your friend, the ShapefileYour friend, the Shapefile
A MisnomerMore the one file
Vectors in one fileData in anotherIndex in anotherOptionally a projection file
A MisnomerMore the one file
Vectors in one fileData in anotherIndex in anotherOptionally a projection file
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