mapping your data 1

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