geographical information systemssuraj.lums.edu.pk/~cs101a07/lectures/lec8.3.pdf1 geographical...

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Geographical Information Geographical Information

Systems (GIS) and Systems (GIS) and

Satellite ImagerySatellite Imagery

Sohaib A KhanSohaib A Khan

CS101: Topical LectureCS101: Topical Lecture

Geographical Information SystemsGeographical Information Systems

�� A computer system that uses A computer system that uses spatially spatially referencedreferenced or or geographical datageographical data to carry out to carry out management management and and analysis analysis taskstasks

�� What type of questions can GIS answer?What type of questions can GIS answer?–– Where are particular features found?Where are particular features found?

–– What geographical patterns exist?What geographical patterns exist?

–– Where have changes occurred over a given time Where have changes occurred over a given time period?period?

–– Where do certain conditions apply?Where do certain conditions apply?

–– What will the spatial implications be if an organization What will the spatial implications be if an organization takes certain action?takes certain action?

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Example ApplicationsExample Applications

�� Searching for appropriate sitesSearching for appropriate sites

–– For example, where to locate a dam?For example, where to locate a dam?

�� Evaluating land use planningEvaluating land use planning

–– For example, protecting natural forestsFor example, protecting natural forests

�� Finding a new homeFinding a new home

Components of a GIS SystemComponents of a GIS System

�� Computer Systems and SoftwareComputer Systems and Software–– Powerful processorPowerful processor

–– Sufficient memorySufficient memory

–– Good quality color monitorGood quality color monitor

–– Data input/output devicesData input/output devices

�� Spatial DataSpatial Data–– Latitude/LongitudeLatitude/Longitude

–– Connection details (roads, trails, railway tracks)Connection details (roads, trails, railway tracks)

–– Attribute Data (amount of snowfall, temperature, population, schAttribute Data (amount of snowfall, temperature, population, schools)ools)

–– Data is often represented in Data is often represented in layerslayers

�� Data Management and AnalysisData Management and Analysis–– Database management systems for efficient storage and retrievalDatabase management systems for efficient storage and retrieval

–– Spatial analysis and transformations (Registration)Spatial analysis and transformations (Registration)

–– QueriesQueries

–– Modeling, predictionsModeling, predictions……

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Latitude and LongitudeLatitude and Longitude

Latitude and LongitudeLatitude and Longitude

http://www3.shastacollege.edu/dscollon/Courses/GEOG%208/geog_8_home.htm

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Satellite ImagesSatellite Images

�� Resolution of a Resolution of a

satellite image is satellite image is

measured in measured in

meters/pixelmeters/pixel

�� Dynamic range Dynamic range

(number of (number of

colors/wavelengths) colors/wavelengths)

that are captured is that are captured is

also importantalso important

LANDSATLANDSAT

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Digital Elevation Map (DEM)Digital Elevation Map (DEM)

�� Resolution is Resolution is

measured in GSD measured in GSD

(ground sampling (ground sampling

distance) and distance) and

accuracy of height accuracy of height

valuevalue

�� E.g. 30m GSDE.g. 30m GSD

Topographic MapsTopographic Maps

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GIS LayersGIS Layers

�� Each Layer shows Each Layer shows

different information. different information.

TopoTopo--map or satellite map or satellite

image often forms the image often forms the

base layerbase layer

1. Base-Level Maps:Since maps are frequently not

available, we will use computer vision

algorithms to extracts roads, water bodies, bridges, cultivated land and

houses from imagery of 1m-per-pixel

resolution

2. Hazard Definition:Rapid disaster assessment is needed to define the footprint of the disaster

3. Inventory Overlay:Overlay of all relevant data, such as

population, houses, schools, medical

facilities. Also track relief disbursements

4. Damage Assessment:Data about damages will be filled in as

it becomes available. Reliability of

data sources will be factored in.

5. Loss Estimation:Based on all these layers, a complete

picture of loss can be constructed

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RegistrationRegistration

�� Aligning images, DEM, maps or other Aligning images, DEM, maps or other

spatial layers, such that the same features spatial layers, such that the same features

overlapoverlap

�� This operation is critical to all GIS This operation is critical to all GIS

applicationsapplications

�� Allows seamless viewing of data from Allows seamless viewing of data from

multiple sourcesmultiple sources

Reference Image

Aerial Image, or mission image

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Satellite image of LUMS campus, approx 1m per pixel resolutionImage credit: Google Earth

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Aerial photograph of LUMS Academic block, taken through a remote controlled airplaneImage credit: Computer Vision Lab, LUMS

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Seamless mosaic made from two images

Finding your Latitude and Longitude using a GPS