intro to gis and remote sensing

Introducing GIS and

Remote Sensing

Introduction to Mapping and GIS

Rowan UniversityThink about all the activity occurring though out a landscape. How can we map, manage and analyze all that is going on? GIS!Think about all the activity occurring though out a landscape. How can we map, manage and analyze all that is going on? GIS!

US Census Data in Excel

Think about keeping information about phenomenon on a landscape. How could you do it?

US Census Data in GIS

GIS organizes that data with a map. But GIS is much more….

Data Types

Aspatial data—data not tied to a location on the earth’s surface

Spatial data—data associated with a location on earth

Much of the information we deal with daily has some spatial component.

What is GIS?

1. Data Management – Manages various kinds of GIS data including vector,

raster, images, tables, other data files– Data models and architectures– Conversion between formats– Import/export utilities– Interacts with RDBMS (SQL Server, Oracle, etc…)

What is GIS?

2. Analysis– Spatially aware data– Attribute and spatial query– Proximity and Overlay– Advanced geoprocessing techniques– Decision support– Flexible, customization• Programming, scripting (to perform analysis)

What is GIS?

3. Visualization– Maps! Maps! Maps!• If a picture is worth a 1000 words…

– Professional cartographic tool– Charts, graphs, tables, etc…– Various coordinate systems– 2D and 3D– Web, desktop, handheld, etc…

What is GIS?

• Data Management – Database View

• Analysis – Model View

• Visualization – Map View

“G” vs. “IS”• GIS uses maps to spatially analyze and search for

patterns in the data that would otherwise not be found. (Content)

• GIS stores, manipulates, and displays data files and relationships in a information system using standard computing practices. (IT)

• With advances in technology, GIS users must now deal with both aspects!

The “G”

• “G” = Geographic– Denotes the concept of spatial location on

Earth’s surface– Importance of relative location (not just where

you are but where you are in relation to everything else)

– Theories and techniques in Geography form the basis of GIS

The “I”

• “I” = Information– Substance (knowledge) about location– Factual and interpretative– Tables + Maps + Analysis– Transformation of table information into spatial

context for analysis– Technology and computer systems

What About the “S” in GIS?

• Systems• Science• Studies• Services

Geospatial?

• Geographic + GIS = “Geospatial”

• Move in recent years to better define the industry and to focus on data and procedures (business) over geographic principles (academic)

• Geospatial includes all subcomponents of GIS embedded in other areas (remote sensing, GPS etc.)

Not Just Computer Cartography

Core of GIS = “Layers”

Importance of Layers in GIS

• Geographic data = Representation of reality

• Reality is complex.• GIS utilizes a layer approach• Each layer only includes

information about one type of phenomenon.

• Data layers must be aligned with one another

Importance of Layers

• Proximity– Finding what is near or within a distance from a

certain location or feature e.g., all houses within 100 yards of a stream

• Overlay– Combining two layers to create new information e.g., habitat based on veg, elevation, and temp

Families of GIS Data Vector mode or coordinate based

Three vector objects exist—points, lines, polygons; these are called “features.”

They are represented by X,Y coordinates sometimes Z (3D), sometimes M (linear reference)

Information about features is (are) called “attributes.” Two types of vector models—topological and object Topological means the data models stores relationships

between vectors Vector objects exist independent of any other nearby

features

Families of GIS Data Raster mode or grid cell

Entire study area is covered by a grid Each cell within grid is given a value Values can be integer or decimal Data can be discrete or continuous Cell size is variable and linked to the file size of the

raster data Areas outside of the grid are ignored Grid must be expanded if those areas are to be

included

Modeling Geospatial Reality

Real World

Vector Model

Raster Model

Coding Vector GIS

RealityReality Vector Mode Model of RealityVector Mode Model of Reality

Coding Vector GIS

PolygonI

PolygonII

PolygonIII

PolygonV

PolygonIV

node

A

node

Bnode

C

node

E node

F

node

G

node

D

RealityReality Vector Mode Model of RealityVector Mode Model of Reality

Coding Raster GIS Data

RealityReality Raster Mode Model of RealityRaster Mode Model of Reality

Coding Raster GIS Data

1 1 1 1 2 3 4 41 1 1 2 2 3 4 41 2 2 2 3 3 4 42 2 2 3 3 4 4 43 3 3 3 5 5 5 51 1 1 1 6 5 5 51 1 1 1 1 5 5 51 1 1 1 1 1 5 5

RealityReality Raster Mode Model of RealityRaster Mode Model of Reality

Advantages of Vector

• Vector data make maps that look more like maps we are use to seeing on paper.

• The shapes of features are accurately represented.

• Vector data can have topology• Vector data is good for managing attributes• Vector data has smaller storage requirement– Only the objects need to be represented in the

database (empty space in-between is not captured)

Disadvantages of Vector

• Complicated data structure• Software must manage many data tables• Not good at representing geographic features

that gradually change over location– For example elevation or moisture in soil

• Slower processing time

Advantages of Raster

• Good at depicting continuously changing surfaces such as elevation or soil moisture

• Grid format is simple data structure• Easier for computer to make analytical

calculations• Ideal for utilizing remote sensing images

Disadvantages of Raster

• Maps can be blocky looking (depending on the size of the grid cells)

• Cells can only be coded for one attribute when there may be more than one attribute at each location

• Can have very large datasets (depending on the size of the grid cell)

• Not topological: adjacency data structure

Remote Sensing

• Remotely-Sensed data is one of the most important sources of data for GIS.

• RS means - Acquiring data from a distance• Usually uses electromagnetic energy– sunlight, radar, laser

• Originally captured on photographic film• Recent platforms utilize digital sensors

Early Remote Sensing Platforms

What kinds of devices collect the data?

• Aircraft– High altitude– Low altitude

• Spacecraft:– Landsat– SPOT– Weather satellites– GeoEye-1

Geosynchronous Orbitwhen the satellite moves at the same speed as the spinning earth – results in the camera staying over the same spot of the earth

Aircraft Images

Black and Whiteor

“Panchromatic”

Sensitive to visible light

Digital Orthographic Photos• Digital photos of the earth• Usually acquired by aircraft• Orthographic means that the photo has all distortion

removed– A regular photo from an airplane will have distortion due to:

• Parallax – effect that distance away from the center point of a photo will always have distortion

• Terrain – the hills and valleys or a land area will cause distortion in the photo

– An orthographic photo is adjusted by computer software to make the image line up with a flat map

You are here

Digital Orthographic Photo - Infrared - 1995

Why Infrared?Why Infrared?

Artificial TurfArtificial Turf

Remote Sensing Mediums• Black and White or “Panchromatic”

– Sensitive to visible light

• True Color– Similar to color film

• Infrared – Sensitive to infrared frequencies that can’t be seen by humans– Developed by military for identifying tanks painted with camouflage – Good for evaluating conditions of vegetation– Good for evaluating moisture in soil

• False-color adjusted– When frequencies of received data are shifted to allow or enhanced human viewing

• Multi spectral– When more than a single “band” of energy is captured– Color is multi-spectral (3 bands)– Some satellites can have 7 or even more “bands” of sensitivity

The Electromagnetic Spectrum

The Visible Spectrum

• The visible spectrum is only a tiny window

• We are blind to 99.99% of the energy in the universe

• We have created devices that allow us to see beyond the range of human vision

Satellite Images

– Weather satellite image: Winter in North America.

What are the spatial units for which data are collected?

• Pixel or Picture Element– Smallest unit of data collection– Features smaller than the pixel size can’t be distinguished

• Pixel Sizes– Landsat MSS = 79 meters– Landsat TM = 30 meters– SPOT = 10 meters– IKONOS = 1 meter– GeoEye-1 = 0.41 meters

Spatialresolution

keeps gettingbetter...

GeoEye-1GeoEye-1GeoEye-1GeoEye-1

1, 3, and10 meters

Spatial resolution keeps getting better...

Temporal Resolution

• Remote sensing images begin to get old as soon as they are taken.

• Satellites repeatedly circle the earth.• Airplanes must be commissioned every time they

photograph (expensive).• NJ aerial photography was taken 1995, 2002, and

2007. Statewide aerials often have to be taken in multiple years. (95/97) (07/08)

• Turnaround is improving: NearMap’s 2cm imagery of Brisbane floods released within 1 week.

What is GIS?

• Now that we’ve learned the essential elements that make up a GIS…

• …and have seen examples of how GIS is being used…

• …let’s take a look at the big picture.

GIS Is Evolving

Projects Systems Networks

Integrated Coordinated Cooperative

Moving to the Internet and Web ServicesMoving to the Internet and Web Services

How is GIS used?

• Sometimes, the best way to learn about GIS is to see how it’s being used…..– Science– Emergency management– Government record-keeping– Business location– Environmental management– Planning– Crime mapping

Creating a Digital Earth

. . . A Nervous System for Spaceship Earth

Measuring and Integrating

Spatial and Thematic Information

Violence in Darfur

• Image shows 2004 & 2006.

• Area too large and dangerous for small peacekeeping force.

• Violence tracked using satellite images.

• Article.

California Wildfires

• LA Times and local residents are mapping the spread of major wildfires.

• Using web-based GIS to present and catalog data.

• Article.

GeoCommons

• GeoCommons is a "mashup" maker• Upload your data – excel or GIS and have it

mapped• Find data others have shared• Make maps, then export to Google Earth

Response to Haitian Earthquake

• Users of OpenStreetMap volunteered time to update the map around Port-au-Prince.

• CrisisCamp volunteers are adding features such as camps, collapsed buildings & recovery efforts.

• How volunteers are using GIS to help in Haiti.