1. GIS
DR. B. L. SINHA
Scientist/ Assistant Professor
(Soil Water Engineering)
DKS College of Agriculture and Research Station
Indira Gandhi Krishi Vishwavidyalay
(Chhattisgarh)
Bhatapara
2.
3. Roger F. Tomlinson, OC (17 November 1933 –
7 February 2014) was an English geographer
and the primary originator of modern
computerised geographic information systems
(GIS), and has been acknowledged as the "father
of GIS."
4. Lesson ObjectivesLesson Objectives
• Understand how a GIS functions
• Understand what a GIS is
• Look at some GIS applications
• Understand how spatial data is
represented in a GIS
5. GIS--What is it?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?
–Systems: the technology
–Science: the concepts and theory
–Studies: the societal context
6. Geographic Information TechnologiesGeographic 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.)
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)
Geographic Information Systems (GISy)
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 GISy.
A GISy provides for storing and manipulating GPS and RS data.
7. GIGI SySystems,stems, ScScience andience and StStudiesudies
Which will we do?Which will we do?
Systems
– technology for the acquisition and management of spatial
information
Science
– 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 GISy and GISc
8. Defining Geographic InformationDefining Geographic Information
Systems (GIS)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, 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)
9. An Inelegant Definition forAn Inelegant Definition for
GISyGISy
A system of integrated computer-based tools for end-to-
end 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
- 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
10. Data vs.Data vs.
InformationInformation
• Data, by itself, generally differs from
information.
• Data is of little use unless it is transformed
into information.
• Information is an answer to a question
based on raw data.
• We transform data into information
through the use of an Information System.
12. What is an Information System?What is an Information System?
13. What is an InformationWhat is an Information
System?System?
Information systems can be very simple,
such as a telephone directory.
Data
Storage
Information System
Query
Information
14. What is an InformationWhat is an Information
System?System?
In the digital environment we use software to
create complex information systems.
15. What is a GIS?What is a GIS?
A means of storing,
retrieving, sorting,
and comparing
spatial dataspatial data
to support some
analytic process.
++
Information SystemInformation System
Geographic PositionGeographic Position
16. GIS links graphical features (entities) to tabular data
(attributes)
What is a GIS?What is a GIS?
GEOGRAPHIC Information System
17. • A GIS is a system (hardware + database
engine) that is designed to efficiently,
assemble, store, update, analyze, manipulate,
and display geographically referencedgeographically referenced
informationinformation (data identified by their
locations).
• A GIS also includes the peoplepeople
operating the system and the datadata that
go into the system.
GIS DefinitionGIS Definition
18. Data can be:
1. Positioned by its known spatial
coordinates.
2. Input and organized (generally in
layers).
3. Stored and retrieved.
4. Analyzed (usually via a Relational
DBMS).
5. Modified and displayed
Key Functions of a GISKey Functions of a GIS
22. Representing SpatialRepresenting Spatial
ElementsElements
Raster
Stores images as rows and columns of numbers with a
Digital Value/Number (DN) for each cell.
Units are usually represented as square grid cells that are
uniform in size.
Data is classified as
“continuous” (such as in an
image), or “thematic”
(where each cell denotes a
feature type.
Numerous data formats
(TIFF, GIF, ERDAS.img etc)
23. Vector
Allows user to specify specific spatial locations and
assumes that geographic space is continuous, not
broken up into discrete grid squares
We store features as sets of X,Y coordinate pairs.
Representing SpatialRepresenting Spatial
ElementsElements
24. Entity RepresentationsEntity Representations
Points - simplest
element
Lines (arcs) - set of
connected points
Polygons - set of
connected lines
We typically represent objects in space as three
distinct spatial elements:
We use these three spatial elements to represent real world features and
attach locational information to them.
25. AttributesAttributes
• In the raster data model, the cell value
(Digital Number) is the attribute. Examples:
brightness, land cover code, SST, etc.
• For vector data, attribute records are linked to
point, line & polygon features. Can store
multiple attributes per feature. Vector
features are linked to attributes by a unique
feature number.
26. Raster vs. VectorRaster vs. Vector
Raster Advantages
The most common data format
Easy to perform mathematical and overlay operations
Satellite information is easily incorporated
Better represents “continuous”- type data
Vector Advantages
Accurate positional information that is best for storing discrete
thematic features (e.g., roads, shorelines, sea-bed features.
Compact data storage requirements
Can associate unlimited numbers of attributes with specific features
28. • Data Assembly
• Data Storage
• Spatial Data Analysis and
Manipulation
• Spatial Data Output
GIS FunctionsGIS Functions
29. GIS FunctionsGIS Functions
Data AssemblyData Assembly
Maps RSI
Intel Database
Manual Digitizing
Scanning
Data Transfer
Direct Entry
Manual Digitizing
Scanning
Data Transfer
Keyboard
GPS
--the common theme is obviously spatial--that is to say, refenced to the earth’s surface
--tomlinson: very general ‘common ground’
--Burroughs: ‘ tool box’, but how linked together?
--NCGIA ‘dbms’ for spatila data, but also adds the concept of process--capture, store, analze and display
--Cowen: adds (1)decison sipport/solve problem perspective and (2) integration
An information system is designed to efficiently capture, store, update, manipulate, analyze, and display DATA.
Remember: Data is NOT Information
Some software is optimized for manipulating databases. MS Access is an example of this. Modern database management programs utilize a relational database. This is a database that references each piece of information once and then keeps track of the relationships among them. In this way
A GIS can be best defined by defining the two parts of the term; geography and information system.
Geography is a science that deals with the earth and life on the earth, while an information system is a way to capture, store, retrieve, sort, and process data to support some analytic process.
What makes the Information System geographic?
The user needs to begin spatially!
A geographic information system (GIS) is a computer-based tool for mapping
and analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public, military and private enterprises for explaining events, predicting outcomes, and planning strategies. Whether siting a military base camp, finding the best soil for a tank to maneuver on, or figuring out the best low level air route for a bombing raid. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. Today, GIS is a multi-billion-dollar industry employing hundreds of thousands of people worldwide. GIS is taught in schools, colleges, and universities throughout the world. Professionals in every field are increasingly aware of the advantages of thinking and working geographically.
A geographic information system (GIS) is a computer-based tool for mapping
and analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public, military and private enterprises for explaining events, predicting outcomes, and planning strategies. Whether siting a military base camp, finding the best soil for a tank to maneuver on, or figuring out the best low level air route for a bombing raid. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. Today, GIS is a multi-billion-dollar industry employing hundreds of thousands of people worldwide. GIS is taught in schools, colleges, and universities throughout the world. Professionals in every field are increasingly aware of the advantages of thinking and working geographically.
GIS PROCESS:
The GIS process involves six steps that are common to what we refer to as the end to end map-making process.
1. Define the spatial problem/question.
.Define the GIS criteria.
.Import or create the data sets
.Perform the GIS analysis
.Create the output
.Decide whether or not the output solves or answers the spatial problem/question. If not, then refine the problem and start the process again.
Spatial data is essentially data with a location. It contains information about the location and shape of, and relationship among geographic features usually stored as coordinates. Spatial data comes in two types, VECTOR and RASTER. Geographic information systems work with two fundamentally different types of geographic models--the "vector model" and the "raster model."
A raster image comprises a collection of grid cells rather like a scanned map or picture. Both the vector and raster models for storing geographic data have unique advantages and disadvantages.
Raster models do not provide precise locational information because space is divided into discrete grid cells. The assumption is that a point can be found within a grid cell.
In the vector model, information about points, lines, and polygons is encoded and stored as a collection of x,y coordinates. A single x, y coordinate, can describe the location of a point feature, such as a control tower. Linear features, such as roads and rivers, can be stored as a collection of point coordinates. Two coordinate pairs are enough to show location and orientation in space. Polygonal features, such as an area of operations and lakes, can be stored as a closed loop of coordinates. The vector model is extremely useful for describing discrete features, but less useful for describing continuously varying features such as soil type.
Spatial data is unique to a GIS in that there are two aspects two it. It has a location and an attribute. The location can be either a geographic coordinate, MGRS coordinate, or any other (x,y) coordinate. The attribute can be either adjectival (describing the object) or have a magnitude (a numerical value).
We need symbolize spatial features in order to be able to associate attribute information.
We can classify different features into different dimensions. Each classification of dimension is a conceptual classification.
Points - “0” dimensionality. No length or Width.
Each point is Discrete in that it can only occupy a given point in space at any given time.
Lines - “1” dimensional. Length, but No Width.
Must have a beginning and an ending point.
Polygons - “2” dimensional. Length and Width.
By adding Width, we can describe a feature as having an area.
Surfaces - “3” dimensional. Length, Width, and Height.
Surfaces have infinite number of values (e.g. Elevation). We say that this type of data is Continuous.
When thinking of spatial elements, we must consider Spatial Scale. Depending on scale, we may want to represent a river as a line or a polygon.
In Raster we explicitly store attribute information and imply its location based on the position within the grid cell structure.
In Vector, we explicitly store the entity information and where the entity is located. We rely on a database structure to link to attribute information.
I n p u t: Before geographic data can be used in a GIS, the data must be converted into a suitable digital format. The process of converting data from paper maps into computer files is called digitizing. Modern GIS technology can automate this process fully for large projects using scanning technology; smaller jobs may require some manual digitizing (using a digitizing table). Today many types of geographic data already exist in GIS-compatible formats. NIMA standard digital data exists in useable formats and can usually be loaded directly into a GIS.
This slide demonstrates heads-up digitizing done in ArcView.
Storage:For small GIS projects it may be sufficient to store geographic information as simple files. There comes a point, however, when data volumes become large and the number of data users becomes more than a few, that it is best to use a database There are many different designs of DBMSs, but in GIS the relational design has been the most useful. A DBMS is nothing more than computer software for managing a database--an integrated collection of data. In the relational design, data are stored conceptually as a collection of tables. Common fields in different tables are used to link them together. This surprisingly simple design has been so widely used primarily because of its flexibility and very wide deployment in applications both within and without GIS.
Analysis and M a n i p u l a t i o n:It is likely that data types required for a particular GIS project will need to be transformed or manipulated in some way to make them compatible with your system. For example, geographic information is available at different scales (street centerline files might be available at a scale of 1:100,000; Topographic line maps data such as ITD at 1:50,000). Before this information can be integrated, it must be transformed to the same scale. This could be a temporary transformation for display purposes or a permanent one required for analysis. GIS technology offers many tools for manipulating spatial data and for weeding out unnecessary data.
The overlay operation is one the most powerful functions in a GIS. It gives the user the ability to place the cartographic representation of thematic data over one another.
However, this is hardly a new function developed by a GIS, but it has been revolutionized by the use of the computerized GIS.
There are many forms of output for a GIS. The first is usually softcopy, namely what you see on the screen. Most Military service member and commanders prefer to have something hardcopy. So more often than not, will require hard copy outputs. A full functioning GIS can do this. It can plot/print given the equipment, the 2D and 3D perspective views on a 2D map.
Talk to each one relevant to the audience.
This slide shows Helicopter Landing Zones within ArcInfo
Often times to map the ocean floor in terms of elevation we use Bathymetric data or DBTB (Digital Bathymetric Data Base). This slide also shows vector data overlaid on top of the data.
This slide shows a proximity analysis of railroads around the Tuzla airport in Bosnia. The buffer is 1000 meters and the areas in blue represent all areas within this 1000 meter range.
CAUTION: DO NOT Make assumptions based on visual correspondence only. The user must obtain evidence on a true cause and effect relationship.
This slide shows an example of flight planning within ArcView through the use of Elevation and Cloud cover data.
CCM (Cross Country Movement) Analysis allows the user to model the cost (e.g. time) it would take for a give object to travel from point A to Point B given the difficulty of the terrain.
For example, if a tank had to travel from point A to point B and you new how fast it could travel on certain road types, soil types, and slopes, you could model the travel cost.
This slide shows a CCM analysis along with a viewshed analysis. The viewshed analysis is used to illustrate what a person can or can not see from a certain point. The two areas denoted by the purple and turquoise angles illustrate two separate viewsheds. The region of overlap shows the area that can be see by both observers from their respective positions.
Facilities Management encompasses a wide range of applications. The examples shown above are:
1. Housing Assessments
2. Power Line Maintenance and Tracking
3. Crime around Schools
4. Water lines/pipes Maintenance and Tracking
This slide shows information on Airfields along with a picture/movie that has been hot-linked to the feature.
The slide shows a Network model, which gives the best route given certain criteria. The green squares denote bridges, which can serve as a limitations within the model. For example, if a bridge was impassible, we could factor that criteria into our model and the route could be recalculated giving us a different solution.
This slide shows a perspective view. A LANDSAT image has been draped over DTED and the buildings have been overlaid over the image and “grown” to represent a 3D view.