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

Centre for Geo-informatics, CSKHPKV, Palampur

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


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


Software

Hardware

GIS?

GIS

GGeographic reference

spatial coordinates of

GISGeographic Information

System

ISInformation system

Database of the


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.


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


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 :


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


•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


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


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


• 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


• 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


Map Layer Overlay

All layers must be

in same projection

and scale


Overlay generates homogenous units – eg. agroecozones

and scale

Centre for Geo-informatics

Earth data representations

Specifying locations

Petrol pump at Tandi (Lahaul

Spiti HP) Referring to next

petrol pump at Leh (J&K)


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


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.


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


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.


Map projections lead to distortions in… ..

SHAPESHAPE

AREA


DISTANCE

DIRECTION

(Angle)


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


� 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


� 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.


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


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

Documents

Introduction to GIS, Remote Sensing & Map Projections