Mapping Your Data Christopher Martin [email_address]

Data Models Two primary data models used when making maps Raster Data Vector Data

Two primary data models used when making maps

Raster Data

Vector Data

Raster Data Consists of discrete cells (think graph paper) Each cell has a discrete value Occur in rows and columns Examples Images (all image types) DEM

Consists of discrete cells (think graph paper)

Each cell has a discrete value

Occur in rows and columns

Examples

Images (all image types)

DEM

Vector 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 Examples Shapefile

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

Examples

Shapefile

Points, Lines, Polygons

Data Sources US Census Bureau Not just population data Generalized Boundary Data ESRI TIGER/LINE NED Data FEMA Q3 Flood Data USGS SEAMLESS Distribution

US Census Bureau

Not just population data

Generalized Boundary Data

ESRI

TIGER/LINE

NED Data

FEMA Q3 Flood Data

USGS

SEAMLESS Distribution

Data Sources (cont’d) NYS GIS Clearing House Membership required Wide variety of data CUGIR NYS and National data Free, huge variety CIGAR Worldwide Elevation Data Columbia University EDS Electronic Data Service

NYS GIS Clearing House

Membership required

Wide variety of data

CUGIR

NYS and National data

Free, huge variety

CIGAR

Worldwide Elevation Data

Columbia University EDS

Electronic Data Service

Data Sources (cont’d) Geography Network Aggregates data from different providers Online Map Server Available

Geography Network

Aggregates data from different providers

Online Map Server Available

Data Quality Meta Data Data about the data All legitimate providers will provide this Available for download or online viewing

Meta Data

Data about the data

All legitimate providers will provide this

Available for download or online viewing

Map Scale The ratio between the distance on the map, and the distance in real life ALWAYS expressed in terms of 1 Usually a ratio E.g. 1:100000, 1:10000 Other scales are available Visual scale is the second most common

The ratio between the distance on the map, and the distance in real life

ALWAYS expressed in terms of 1

Usually a ratio

E.g. 1:100000, 1:10000

Other scales are available

Visual scale is the second most common

Coordinate Systems Two types of coordinate systems used in geography Spherical (Latitude and Longitude) Typically not used in ArcGIS Always used in Google Earth Rectangular Predominantly used in Arc and GIS in general UTM - Universal Transverse Mercator State Plane Other countries have their own.

Two types of coordinate systems used in geography

Spherical (Latitude and Longitude)

Typically not used in ArcGIS

Always used in Google Earth

Rectangular

Predominantly used in Arc and GIS in general

UTM - Universal Transverse Mercator

State Plane

Other countries have their own.

Spherical Coordinate System Based on meridians and parallels Latitude (parallels) Measured northward or southward from the equator to poles Ranging 0-90 0 north or south The measuring units are degrees, minutes, and seconds, 1 0 = 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 0-180 0 east or west The measuring units are the same as Latitude Length of one degree longitude reduces toward poles

Based on meridians and parallels

Latitude (parallels)

Measured northward or southward from the equator to poles

Ranging 0-90 0 north or south

The measuring units are degrees, minutes, and seconds, 1 0 = 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 0-180 0 east or west

The measuring units are the same as Latitude

Length of one degree longitude reduces toward poles

Rectangular Coordinate Systems Convert the curved surface of the earth onto a flat surface Standard cartesian coordinates, but different names X is called “Easting” Y is called “northing”

Convert the curved surface of the earth onto a flat surface

Standard cartesian coordinates, but different names

X is called “Easting”

Y is called “northing”

Universal Transverse Mercator Based on the mercator map projection Divides the world into 60 zones Starts at 180 degrees longitude Each zone is 6 degrees of longitude wide Labeled 1-60 going eastward And 20 Rows Labeled C-X, skipping I and O Intersection of Row and Zone is a Quadrangle Usually referred to as “quad” Measurement unit is meters

Based on the mercator map projection

Divides the world into 60 zones

Starts at 180 degrees longitude

Each zone is 6 degrees of longitude wide

Labeled 1-60 going eastward

And 20 Rows

Labeled C-X, skipping I and O

Intersection of Row and Zone is a Quadrangle

Usually referred to as “quad”

Measurement unit is meters

Universal Transverse Mercator

State Plane Used exclusively in the United States The US is divided into 120 zones Follow state and county lines Each state has its own map projection North to South states use Mercator East to West states use Lambert Conformal Conic

Used exclusively in the United States

The US is divided into 120 zones

Follow state and county lines

Each state has its own map projection

North to South states use Mercator

East to West states use Lambert Conformal Conic

State Plane

So What?

Map 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 coordinates Classified two ways By the surface projected onto By 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 coordinates

Classified two ways

By the surface projected onto

By what gets distorted

Surfaces Developable Surfaces What kind of shape will we use? It has to be 2D, and we need to be able to “unroll” it The earth gets “wrapped” in the shape, and the surface is transferred to the 2D shape Types Cylindrical, Conic, Azimuthal

Developable Surfaces

What kind of shape will we use?

It has to be 2D, and we need to be able to “unroll” it

The earth gets “wrapped” in the shape, and the surface is transferred to the 2D shape

Types

Cylindrical, Conic, Azimuthal

Cylindrical Projections Mercator Transverse Mercator

Mercator

Transverse Mercator

Azimuthal Projections Top down view Or Bottom Up

Top down view

Or Bottom Up

Conic Projections Used to focus on a particular continent Least amount of distortion for east-west direction

Used to focus on a particular continent

Least amount of distortion for east-west direction

Distortion Projections All maps distort It’s inevitable Projections can be grouped based on WHAT is distorted Conformal - shapes are the same Equal-Area - areas are the same Equidistant - distances are the same*

All maps distort

It’s inevitable

Projections can be grouped based on WHAT is distorted

Conformal - shapes are the same

Equal-Area - areas are the same

Equidistant - distances are the same*

Projection Example

Measuring Distortion

Comparisons of Projections Map Projection Poster

Map Projection Poster

Map Types Thematic Maps Not reference maps Four main types Choropleth Map Proportional Map Isarithmic Map (contour) Dot Map

Thematic Maps

Not reference maps

Four main types

Choropleth Map

Proportional Map

Isarithmic Map (contour)

Dot Map

Choropleth Map Shaded Areas The “color” of the shade varies based on measurement of our variable

Shaded Areas

The “color” of the shade varies based on measurement of our variable

Isarithmic Map Also known as Contour Maps We draw lines to connect separate variables that have the same value

Also known as Contour Maps

We draw lines to connect separate variables that have the same value

Proportional Symbol Map Uses symbols The size of the symbol varies according to the variable

Uses symbols

The size of the symbol varies according to the variable

Dot Density Map Uses dots Size is uniform, but the concentration represents changes in the variable

Uses dots

Size is uniform, but the concentration represents changes in the variable

Cartograms Are NOT maps Area is not preserved Area of the geographic regions varies by variable Two primary types Area Area gets larger or smaller depending on the variable Distance Nodes or places can be closer or farther depending on realtive distance

Are NOT maps

Area is not preserved

Area of the geographic regions varies by variable

Two primary types

Area

Area gets larger or smaller depending on the variable

Distance

Nodes or places can be closer or farther depending on realtive distance

Cartogram

File Formats Shapefile A collection of points, lines and polygons Tabular data values assocated with each DEM Raster data, each cell represents elevation Comes in different resolutions

Shapefile

A collection of points, lines and polygons

Tabular data values assocated with each

DEM

Raster data, each cell represents elevation

Comes in different resolutions

Getting to Know ArcGIS ArcMap Your main tool. Handles map layout, projection, data classification, analysis ArcCatalog Asset management program. Maps drives of data for easy access, displays meta data, manages database connections ArcView Older version of ArcMap. ArcScene 3D rendering

ArcMap

Your main tool. Handles map layout, projection, data classification, analysis

ArcCatalog

Asset management program. Maps drives of data for easy access, displays meta data, manages database connections

ArcView

Older version of ArcMap.

ArcScene

3D rendering

Your friend, the Shapefile A Misnomer More the one file Vectors in one file Data in another Index in another Optionally a projection file

A Misnomer

More the one file

Vectors in one file

Data in another

Index in another

Optionally a projection file