Introduction to GIS, Remote Sensing & Map Projections
Transcript of Introduction to GIS, Remote Sensing & Map Projections
Introduction to GIS, Remote Sensing & Map
Centre for Geo-informatics
Remote Sensing & Map Projections
Contents
The preliminaries….1
Geographic Information System2 Geographic Information System2
3 Remote Sensing
4 Image Data Characteristics
55 Map projections
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Map projections
6 Global Positioning System
57 Applications of GIS/RS
The preliminaries….
�Geography: Study of earth’s features and �Geography: Study of earth’s features and patterns of their variations with spatial
location and time
�Spatial data: data that is specific to a location
�Map: The traditional method of presenting
and analyzing spatial data in 2-dimensions
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and analyzing spatial data in 2-dimensions
� …maps shape the way we visualize and analyze
spatial data
GIS--What is it?
�Geographic/Geospatial Information
� information about places on the earth’s surface
� knowledge about “what is where when”
(Don’t forget time!)
� Geographic/geospatial: synonymous
�GIS--what’s in the S?�GIS--what’s in the S?
� Systems: the technology
� Science: the concepts and theory
� Studies: the societal context
GIS
Geoinformatics
Policy/
procedures
People Database
G.I.S.
Geoinformatics is a cycle
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Software
Hardware
GIS?
GIS
GGeographic reference
spatial coordinates of
GISGeographic Information
System
ISInformation system
Database of the
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spatial coordinates of
features on the
surface of the earth -
MAP
Database of the
feature (contains
various properties
described as
attributes
Components of G.I.S.
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Policy and
Procedures for
Resource
Management
Geographic Information Technologies
�Global Positioning Systems (GPS)� a system of earth-orbiting satellites which can provide
precise (100 meter to sub-cm.) location on the earth’s surface (in lat/long coordinates or equiv.)surface (in lat/long coordinates or equiv.)
�Remote Sensing (RS)� use of satellites or aircraft to capture information about the
earth’s surface
� Digital ortho images a key product (map accurate digital photos) – rectified aerial photographs
�Geographic Information Systems (GIS)�Geographic Information Systems (GIS)� Software systems with capability for input, storage,
manipulation/analysis and output/display of geographic (spatial) information
GPS and RS are sources of input data for a GIS.
A GIS provides for storing and manipulating GPS and RS data (not restricting to these).
GI Systems, Science and StudiesWhich will we do?� Systems
� technology for the acquisition and management of spatial information
� Science
� comprehending the underlying conceptual issues of representing data and � comprehending the underlying conceptual issues of representing data and processes in space-time
� the theory and concepts behind the technology
Introduce enough of the science to apply the systems correctly and understand their capabilities and limitations
� Studies
� understanding the social, legal and ethical issues associated with the application of GISystem and GIScience
Primary objective of our training is: Combine hands-on technical
training with an understanding of the underlying science, and an
emphasis on multidisciplinary applications
Defining Geographic Information Systems (GIS)
• The common ground between information processing and the many
fields using spatial analysis techniques. (Tomlinson, 1972)
• A powerful set of tools for collecting, storing, retrieving, transforming, • A powerful set of tools for collecting, storing, retrieving, transforming,
and displaying spatial data from the real world. (Burroughs, 1986)
• A computerised database management system for the capture,
storage, retrieval, analysis and display of spatial (locationally defined)
data. (NCGIA, 1987)
• A decision support system involving the integration of spatially
referenced data in a problem solving environment. (Cowen, 1988)
& many many more……. �& many many more……. �
An informal Definition for GISy
A system of integrated computer-based toolsfor processing (capture, storage, retrieval, analysis, display) of data using location on for processing (capture, storage, retrieval, analysis, display) of data using location on the earth’s surface for interrelation in support of operations management, decision making, and science.
• set of integrated tools for spatial analysis
• encompasses end-to-end processing of data• encompasses end-to-end processing of data– capture, storage, retrieval, analysis/modification, display
• uses explicit location on earth’s surface to relate data
• aimed at decision support, as well as on-going operations and scientific inquiry
GIS: system is
� A map with a database behind it.
� A virtual representation of the real world and its infrastructure. world and its infrastructure.
� A consistent “as-built” of the real world, natural and manmade
Which is
� queried to support on-going operations
� summarized to support strategic � summarized to support strategic decision making and policy formulation
� analyzed to support scientific inquiry
Why Study GIS?� 80% of local government activities estimated to be geographically
based
� zoning, public works (streets, water supply, sewers), garbage collection, land ownership and valuation, public safety (fire and police)
� a significant portion of government has a geographical component
� natural resource management
� highways and transportation
� businesses use GIS for a very wide array of applications
� retail site selection & customer analysis
� logistics: vehicle tracking & routing
� natural resource exploration (petroleum, etc.)
� precision agriculture
� civil engineering and construction� civil engineering and construction
� Military and defense � Battlefield management
� Satellite imagery interpretation
� scientific research employs GIS
� Agriculture, veterinary, fisheries, environmental etc
The major areas of GIS application
� Local Government� Public works/infrastructure management (roads, water, sewer)
� Planning and environmental management
� property records and appraisal � property records and appraisal
� Real Estate and Marketing� Retail site selection, site evaluation
� Public safety and defense� Crime analysis, fire prevention, emergency management,
military/defense
� Natural resource exploration/extraction� Natural resource exploration/extraction� Petroleum, minerals, quarrying
� Transportation� Airline route planning, transportation planning/modeling
� Public health and disease outbreak studies…
� The Geospatial Industry ( we @CGRT)� Data development, application development, programming,training
Examples of Applied GIS
� Urban Planning, Management & Policy� Zoning, subdivision planning
� Land acquisition
� Economic development
� Civil Engineering/Utility� Locating underground facilities
� Designing alignment for freeways, transit
� Coordination of infrastructure maintenance� Economic development
� Code enforcement
� Housing renovation programs
� Emergency response
� Crime analysis
� Tax assessment
� Environmental Sciences� Monitoring environmental risk
� Modeling stormwater runoff
� Management of watersheds, floodplains, wetlands, forests,
maintenance
� Business� Demographic Analysis
� Market Penetration/ Share Analysis
� Site Selection
� Education Administration� Attendance Area Maintenance
� Enrollment Projections
� School Bus Routing
� Real Estate� Neighborhood land pricesfloodplains, wetlands, forests,
aquifers
� Environmental Impact Analysis
� Hazardous or toxic facility siting
� Groundwater modeling and contamination tracking
� Political Science� Redistricting
� Analysis of election results
� Predictive modeling
� Neighborhood land prices
� Traffic Impact Analysis
� Determination of Highest and Best Use
� Health Care� Epidemiology
� Needs Analysis
� Service Inventory
What GIS Applications Do:manage, analyze, communicate
� make possible the automation of activities involving geographic data
� map production
� calculation of areas, distances, route lengths
� measurement of slope, aspect, viewshed
� logistics: route planning, vehicle tracking, traffic management
� allow for the integration of data generally confined to independent domains (e.g property maps and air photos).
� by tieing data to maps, permits the subsequent communication of complex spatial patterns (e.g environmental sensitivity).
� provides answers to spatial queries (how many ATMs are located in a diameter of 100m from a shopping mall?)
� perform complex spatial modelling (what if scenarios for
transportation planning, disaster planning, resource management, utility design)
GIS System Architecture and Components
Data Input
Query InputGeographic
Database
Output: Display and
Reporting
Transformation and
Analysis
Knowledge Base for GIS
Computer
Science/MIS
graphics
GIS
Application Area:
public admin.
planning
geology
mineral exploration
forestry
site selection
marketing
graphics
visualization
database
system administration
security
Geography marketing
civil engineering
criminal justice
surveying
and related:
cartography
geodesy
photogrammetry
landforms
spatial statistics.The convergence of technological fields and
traditional disciplines.
GIS - integrating technology
Earth’s surface representation
common
locational
reference
Layers
•Hydrography•Elevation•Infrastructure•Soils•Landuse etc
Attributes
•Water•Heights•Buildings•Soil types
Earth’s surface representation
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reference
Registration of all layers
Information from GIS
Location :
Where are specific features found ?
Conditions :Conditions :
Where do certain conditions apply ?
Trends :
What changes have occurred over time ?
Spatial Patterns :
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Spatial Patterns :
What spatial patterns exist ?
What if …:
What will be the consequences of decisions
(GIS+Models)
The GIS Data Model: Purpose
�allows the geographic features in real world locations to be digitally represented and locations to be digitally represented and
stored in a database so that they can be abstractly presented in map (analog) form,
and can also be worked with and manipulated to address some problem
(see associated diagrams)
Data in GIS
•GIS holds spatial information
in independent layers
•integrates layers by
GIS - integrating technology
•integrates layers by
registering them to a common
locational reference.
•thematic layers can all be
made visible at the same time
or selectively and linked by
common location
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•allows overlaying to get
homogenous land units and
other types of information
• allows collating data from
several layers for any location
The GIS Model: example
roads
Here we have three layers or themes:--roads,
--hydrology (water),
--topography (land elevation)
They can be related because precise longitude
hydrology
They can be related because precise geographic coordinates are recorded for each theme.
longitude
longitude
Layers are comprised of two data types
•Spatial data which describes location (where)•Attribute data specifing what, how much,
when
topography
longitude
when
Layers may be represented in two ways:
•in vector format as points and lines
•in raster(or image) format as pixels
Spatial and Attribute Data
�Spatial data (where)� specifies location
� stored in a shape file, geodatabase or similar � stored in a shape file, geodatabase or similar geographic file
�Attribute (descriptive) data (what, how much, when)� specifies characteristics at that location, natural or
human-createdhuman-created
� stored in a data base table
GIS systems traditionally maintain spatial and attribute data separately, then “join” them for display or analysis
Representing Data with Raster Models
�area is covered by grid with (usually) equal-sized, square cellssized, square cells
�attributes are recorded by assigning each cell a single value based on the majority feature (attribute) in the cell, such as land use type.
�Image data is a special case of raster data in which the “attribute” is a reflectance value [cells in image data often called pixels(picture elements)]
Representing Data with Vector Models
�The fundamental concept of vector GIS is that all geographic features in the real work that all geographic features in the real work can be represented either as:
�points or dots (nodes): trees, poles, fire plugs, airports, cities
�lines (arcs): streams, streets, sewers,�lines (arcs): streams, streets, sewers,
�areas (polygons): land parcels, cities, districts, forest, rock type
Vector and Raster representations
�Vector formats
� Discrete representations of reality
X,Y X,Y X,Y
X,Y
�Raster formats
� square cells to model reality
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Reality(A highway)
X,Y
Rows
ColumnsAdopted from: ESRI
Real World
Vector and Raster representations
0 1 2 3 4 5 6 7 8 9
0 R T
1 R T
2 H R
Real World
Vector RepresentationRaster Representation
point2 H R
3 R
4 R R
5 R
6 R T T H
7 R T T
8 R
9 R
line
polygon
Vector Data model
Points / nodesPoints / nodes
Lines / arcs
Areas / Polygons
Vector Vector
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Areas / Polygons
•points in sequence build lines
•lines have direction/ordering of nodes
•lines in sequence build polygons
•points lines and areas
- stored in corresponding datafiles
- stored with topology (connections)
Spatial data Generation-Vector
Digitizer/ screen
• discretize lines into points (nodes) and digitize as straight-
line segments called vectors or arcs.
• feature attribute tables of points ( X,Y coordinates), lines
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• feature attribute tables of points ( X,Y coordinates), lines
(lengths and topology) and areas (geometry and topology) and
are generated and stored in tables in a database
• points, lines and areas have independent tables
• Add attribute data (properties) to database
Spatial data Generation-Raster
• map is represented by rectangular or square cells
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• map is represented by rectangular or square cells
• each cell is assigned a value based on what it represents
• attribute data are assigned by user to cells
Raster-Vector format conversions
Vector to raster - easy
Raster to vector - hard
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Map Layer Overlay
All layers must be
in same projection
and scale
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Overlay generates homogenous units – eg. agroecozones
and scale
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Earth data representations
Specifying locations
Petrol pump at Tandi (Lahaul
Spiti HP) Referring to next
petrol pump at Leh (J&K)
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petrol pump at Leh (J&K)
GIS : Representing the Earth
�Geoid and Spheroids: modeling the earth�Geoid and Spheroids: modeling the earth
�Latitude and Longitude: position on the model
�Datums and Surveying: measuring the model
�Map Projections: converting the model to 2-D
�Scale: sizing the model
The Shape of the Earth3 concepts� topographic surface
� the land/air interface
� complex (rivers, valleys, etc) and difficult to model
� geoid
� a continuous surface which is perpendicular at every point to the direction of
gravitygravity
� approximates mean sea-level in open ocean without tides, waves or swell
� “that surface to which the oceans would conform over the entire earth if free to
adjust to the combined effect of the earth's mass attraction and the centrifugal
force of the earth's rotation.” Burkhard 1959/84
� satellite observation (after 1957) showed it to be somewhat irregular ‘cos of
local variations in gravity resulting from the uneven distribution of the earth’s
mass.
� Spheres and spheroids (3-dimensional circle and ellipse)
� mathematical models used to approximate the geoid and provide the basis for
accurate location (horizontal) and elevation (vertical) measurement
� sphere (3-dimensional circle) with radius of 6,370,997m considered ‘close enough’ for small scale maps (1:5,000,000 and below - e.g. 1:7,500,000)
� spheroid (3-dimensional ellipse, flattened at the poles) should be used for larger scale maps of 1:1,000,000 or more (e.g. 1:24,000)
Relationship of Land Surface to Geoid and Spheroid
Land surface
GPS (global positioning system) measures elevation relative to spheroid.Traditional surveying via leveling measures elevation relative to geoid.
surface
Spheroid (math model)
mean sea surface (geoid)
Geoid(undulates due to
gravity)
(math model)
Note that elevation causes distances measured on ground to be greater than on the spheroid. Corrections may be applied.
Geographical Coordinate System (GCS)
�A geographical coordinate system (GCS) uses a three dimensional spherical surface to define three dimensional spherical surface to define
locations on the earth.
�A point is referenced by its longitude and
latitude values. Longitude and latitude are angles measured from the earth’s center to a point on the earth’s surface. The angles often
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point on the earth’s surface. The angles often
are measured in degrees.
�Latitude and Longitude: location on the spheroid
Centre for Geo-informatics, CSKHPKV, PalampurThe world as a globe showing the longitude and latitude values.
Latitude and longitude measured in Decimal Degrees or in Degrees, Minutes, and
Seconds (DMS).
For most geographic coordinate systems, the prime meridian is the longitude that
passes through Greenwich, England. Other countries use longitude lines that pass
through Bern, Bogota, and Paris as prime meridians.
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Seconds (DMS).
Latitude values (relative to the equator): -90°[South Pole] to +90°[North Pole].
Longitude values (relative to the prime meridian): -180°[traveling west] to 180°[traveling
east].
If the prime meridian is at Greenwich, then Australia, which is south of the equator
and east of Greenwich, has positive longitude values and negative latitude values.
Geodetic datum
• a set of parameters defining a coordinate system, including:
Indian Standard
World Standard
system, including:
– the spheroid (earth model)
– a point of origin and an orientation relative to earth’s axis of rotation (ties spheroid
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rotation (ties spheroid to earth)
(Source: Mishra, 1996)
Map Projections: the concept
� A method by which the curved 3D surface of the earth is
represented on a flat 2D map surface.
� a two dimensional representation, using a plane coordinate � a two dimensional representation, using a plane coordinate
system, of the earth’s three dimensional sphere/spheroid
� location on the 3D earth is measured by latitude &
longitude;
� location on the 2D map is measured by x,y Cartesian
coordinatescoordinates
� choice of map projection does not change a location’s
lat/long coords, only its XY coords.
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Map projections lead to distortions in… ..
SHAPESHAPE
AREA
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DISTANCE
DIRECTION
(Angle)
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The graticule of a geographic coordinate system is projected onto a cylindrical
projection surface.
Conic projection
� The most simple conic projection is tangent to the globe along a line
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� The most simple conic projection is tangent to the globe along a line of latitude. This line is called the standard parallel. The meridians are projected onto the conical surface, meeting at the apex, or point, of the cone.
� Parallel lines of latitude are projected onto the cone as rings.
� The cone is then ‘cut’ along any meridian to produce the final conic projection, which has straight converging lines for meridians and concentric circular arcs for parallels. The meridian opposite the cut line becomes the central meridian.
Cylindrical projections
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� Meridians are geometrically projected onto the cylindrical surface, and parallels are mathematically projected. This produces graticular angles of 90 degrees. The cylinder is ‘cut’ along any meridian to produce the final cylindrical projection. The meridians are equally spaced, while the spacing between parallel lines of latitude increases toward the poles.
Planar projections
� Planar projections project map
data onto a flat surface touching
the globe. A planar projection is
also known as an azimuthal also known as an azimuthal
projection or a zenithal projection.
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The Gnomonic projection views the surface data from the center of the earth,
The Stereographic projection views it from pole to pole.
The Orthographic projection views the earth from an infinite point, as if from deep space.
BEHRMANN EQUAL AREACYLINDRICAL projection
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Shape: Shape distortion is minimized near the standard parallels (30N and 30S).
Area: Area is maintained.
Direction: Directions are generally distorted.
Distance: Directions are generally distorted except along the equator.
USES AND APPLICATIONS: Only useful for world maps.
Map Scale
Scale: ratio of distances on map to distances
on earth’s surface
1 cm = 2.5 km or 1:250000
Km
Map scale determines the size and shape of features
city• Large scale
1:500 1:24000
city
• Small scale1:250000
1:24000
Source: ESRI
Standard Scales:
1:1000,000 Country level (1mm = 1000 m) 1:1000,000 Country level (1mm = 1000 m)
1: 250, 000 State level (1 mm = 250 m)
1: 50,000 District level (1mm = 50 m)
1: 12,500 Micro level (1mm = 12.5 m)
Survey of India Maps (topographic maps) are available at all
above scales except 1:12,500
Building a GIS
� Data base design Area boundaries
Co-ordinate system
data layers
features for each layerfeatures for each layer
attributes for each feature type
coding and organizing attribute
data
� Entering spatial data from maps for each layer
� Creating topology
� Entering attribute data
� Managing the data base
� Presenting maps in customized form
Summary
� GIS is a computer based tool for geographic analysis
� It is not a map, nor does is store maps. IT STORES
DATADATA
� Central concept :
� Separation of spatial and attribute data for entry &
� Their linkage for analysis
� Database management concepts are central to GIS
� Spatial data in two formats: Vector & Raster� Spatial data in two formats: Vector & Raster
� Keep note of map projections / scale to transform
information to real-world terms
GIS use
Resource Inventory
(Data Base Management)Level-1
(Data Base Management)
Integration of Different Layers
(Overlay)Level-2
Interfacing with simulation
models – GIS based DSS
Level-3