geographical information systemssuraj.lums.edu.pk/~cs101a07/lectures/lec8.3.pdf1 geographical...
TRANSCRIPT
1
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?
2
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……
3
Latitude and LongitudeLatitude and Longitude
Latitude and LongitudeLatitude and Longitude
http://www3.shastacollege.edu/dscollon/Courses/GEOG%208/geog_8_home.htm
4
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
5
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
6
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
Pre
para
tio
nA
ssessm
en
t
Resp
on
se
R
eco
very
7
8
9
10
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
11
12
13
Satellite image of LUMS campus, approx 1m per pixel resolutionImage credit: Google Earth
14
Aerial photograph of LUMS Academic block, taken through a remote controlled airplaneImage credit: Computer Vision Lab, LUMS
15
Seamless mosaic made from two images
Finding your Latitude and Longitude using a GPS