gis
DESCRIPTION
GIS notes(sushil kulkarni) for MCS part 1 and Msc IT part1 studentsTRANSCRIPT
Sushil Kulkarni 1
Sushil Kulkarni 2
111...SSStttaaarrrttteeerrr……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….........333
222...GGGIIISSS dddeeefffiiinnniiitttiiiooonnn………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………...………...333
333...GGGIIISSS HHHiiissstttooorrryyy………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………555
444... SSSoooffftttwwwaaarrreeesss……………………………………………………………………………………………………………………………………………………………………………………………………………..55
444...111... MMMAAAPPPIIINNNFFFOOO PPPrrrooofffeeessssssiiiooonnnaaalll vvv 666...555………………………………………………………………………………………………………………………………………………………………………...... 555
444...222... AAARRRCCC GGGIIISSS………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………...... 666
555... DDDaaatttaaa SSStttrrruuuccctttuuurrreeesss iiinnn GGGIIISSS ………………………………………………………………………………………………………………………………………………………………………………………………………………………666
666... DDDaaatttaaa mmmaaannnaaagggeeemmmeeennnttt rrreeeqqquuuiiirrreeemmmeeennntttsss ooofff GGGIIISSS………………………………………………………………………………………………………………………………………………...... 888
666...111 DDDaaatttaaa mmmooodddeeellliiinnnggg aaannnddd rrreeeppprrreeessseeennntttaaatttiiiooonnn………………...………………………………………………………………………………………………………………………………... 888 666...222 DDDaaatttaaa bbbaaassseee mmmaaannnaaagggeeemmmeeennnttt aaannnddd aaannnaaalllyyysssiiisss………………………………………………………………………………………………………………………………………......111111 666...333 DDDaaatttaaa IIInnnttteeegggrrraaatttiiiooonnn………………………………………………………………………………………………………………………………………………………………………………………………………………………...111111 666...444 DDDaaatttaaa cccaaappptttuuurrreee………………………………………………………………………………………………………………………………………………………………………………………………………………………………………......111111
777 GGGIIISSS dddaaatttaaa ooopppeeerrraaatttiiiooonnnsss………………………………………………………………………………………………………………………………………………………………………………………………………………………………... 111111
GGGEEEOOOGGGRRRAAAPPPHHHIIICCC IIINNNFFFOOORRRMMMAAATTTIIIOOONNN SSSYYYSSSTTTEEEMMM
Sushil Kulkarni 3
11..SSttaarrtteerr
Originally the purpose of maps was for navigation only because explorers and traderswanted to know how to travel from one place to another through uncharted waters or overunexplored lands. Later, after the invention of paper and as the science of cartographyadvanced, people became interested in studying the relationships between natural andmanmade features on the Earth's surface. Recently, the demand for maps of thetopography and specific themes of the earth's surface, such as natural resources, hasaccelerated greatly.
Scientists wanted to study man's use of the land, which led to the study of spatialdistributions of such things as soil, people, vegetation, climate, etc. First an inventory had tobe taken via which data was collected and recorded. Due to the large volume of data andlack of mathematical tools qualitative methods of classification and mapping were usedinitially. With the development of appropriate mathematical tools and the availability of thedigital computer spatial analysis and quantitative thematic mapping have mushroomed.
Before computers the spatial database was a drawing on a piece of paper or film. Varioussymbols, colors and text codes together with legends were used to display geographicalentities. Other additional information was given in accompanying narratives.
Because the paper map was the spatial database the information it contained had to becompromised, namely:
1. data volume was greatly reduced => local detail lost2. map drawn extremely accurately and presentation clear
The collection and compilation of data and the publication of a printed map is costly andtime-consuming. To extract a single theme from a general-purpose map by hand is veryexpensive. The need for information about how the earth's surface is changing annually,monthly, weekly, daily, and even hourly makes conventional mapping techniquesinadequate and simply impossible by hand.
GIS is the mapping tool, which forms a marriage between remote sensing, earthboundsurvey, and cartography. Be aware that computer-aided design drawing software can createtheme, display and print geo referenced data just like a GIS software package but that notopology is present to permit spatial analyses to be performed.
22..GGIISS ddeeffiinniittiioonn
The definition of GIS states that it is software, which can acquire, store, retrieve, andanalyze information describing physical properties of the geographical world. The scope ofGIS is for two types of data:
Sushil Kulkarni 4
(1) spatial data that includes maps, digital images, administrative and politicalboundaries such as roads; transportation networks, physical data such as rivers; soil-characteristics; climatic regions; land elevations.
(2) non-spatial data, such as census counts, economic data, and sales or marketinginformation
Following figure encapsulates these data:
A GIS is designed to allow a user to ask an almost unlimited number of spatial questions asfollows:* Where is object A?* Where is A in relation to place B?* How many occurrences of type A are there within a distance D of B?
Sushil Kulkarni 5
* What is the value of function Z at position X?* How large is B (area, perimeter, and inclusion count)?* What is the result of intersecting various kinds of spatial data?* What is the path of least cost, resistance, or distance along the ground from X to Y
along pathway P?* What is at points X1, X2,...?* What objects are next to objects having certain combinations of attributes?
33..GGIISS HHiissttoorryy
The father of GIS is recognized to be Dr. Ian McArth, a landscape designer, who published abook in 1969 dealing with spatial representations of features in 2 and 3 dimensions. In the1970s Dana Tomlin, a Ph.D. student at the Harvard Graphics Lab, developed the first rasterGIS program called MAP. This software was in the public domain so others developed itfurther. These individuals were Dr. Duane F. Marble, Dept. of Geography, The Ohio StateUniversity, Columbus OH who developed OSU MAP-for-the-PC in the 1980s and Dr. JosephBerry, Berry & Associates, Ft. Collins CO. who developed PMAP. The 1980s saw a greatprofileration of start-up GIS companies but in the last five years many have disappearedsuch as PAMAP from Victoria, B.C. and SPANS from Ottawa, Canada. One of thesecompanies, Environmental Systems Research Institute (ESRI), Redlands, CA under theleadership of Dr. Jack Dangermond, developed the concept of linking attributes stored in adatabase to map features in 1984. This simple idea revolutionized the GIS industry. Atpresent ESRI has captured about 90 percent of the GIS user community and has clients allover the world. However there are still others GIS software vendors that are alive and doingwell such as MAPINFO, MGA from Intergraph, IDRISI from Clark University, ArcView GISto name a few.
44.. SSooffttwwaarreess
Following are two popular softwares:
444...111... MMMAAAPPPIIINNNFFFOOO PPPrrrooofffeeessssssiiiooonnnaaalll vvv 666...555
With MAPINFO you can display data as points, as thematically shaded regions, as pie or barcharts, as districts, etc. You can perform geographic operations such as redistricting,combining and splitting geographic objects, and buffering. From MAPINFO you can performdata powerful SQL queries and remotely access your data. For instance, it calculatesdistances between customers and stores, compute which branch stores are the closest toyour biggest customers and color-code store symbols by sales volume.
Sushil Kulkarni 6
444...222... AAARRRCCC GGGIIISSS
ArcGIS is the collective name for three products - ArcView, ArcEditor, and ArcInfo. Theseproducts are built on a common interface and core capability with each product offering adifferent level of functionality. The basic building blocks of ArcGIS are:
* ArcMap - for displaying and querying maps* ArcCatalog - for managing geographic data* ArcToolbox - for setting map projections and converting data
a. ArcMap
In ArcMap, you make maps from layers of spatial data, choose colors and symbols, queryattributes, analyze spatial relationships, and design map layouts. The ArcMap interfacecontains a list (or table of contents) of the layers in the map, a display area for viewing themap, and menus and tools for working with the map.
b. ArcCatalog
Spatial data can be browsed on your computer's hard disk, on a network or on the Internet.You can search for spatial data, review it, and add it as layers to ArcMap. ArcCatalog hastools for creating and viewing metadata (information about spatial data such as who createdit and when, its intended use, its accuracy, etc.). ArcCatalog manages spatial data thatcome in a variety of formats. The geodatabase is a new spatial data format designedspecifically for ArcGIS.
c. ArcToolbox
With this ArcGIS building block spatial data can be converted from one format to anotherusing a set of tools. Most tools have a wizard interface that walks you through each step ofa task. Also the map projection of data can be changed. About fifty map projections are incommon use. Over 300 different models exist (and are recognized by ArcMap) to describethe exact shape of the earth. There are 36 commonly used tools for data conversion andmanagement in ArcToolbox for ArcView and ArcEditor
55.. DDaattaa SSttrruuccttuurreess iinn GGIISS
All geographical data can be reduced to 3 basic topological concepts -- the point, the line,and the area. A label is also needed to identify what the entity is, e.g. a section of railroadline could be represented by a line consisting of a starting and ending x, y coordinate andthe label "railroad".
A map is a set of points, lines, and areas that are defined both by their location in space
Sushil Kulkarni 7
with reference to a coordinate system and by their non-spatial attributes.The map legend is the key linking non-spatial attributes to the spatial entities. Colors,symbols and shading are employed to visually display non-spatial information.Map data is stored in a computer in the form of files, which must be accessed and cross-referenced quickly. Therefore, the organization of the data elements comprising such files isvery important. Database management systems (software) are used to control data input,output, storage, and retrieval.
Consider the example of simple map M with two polygons labelled I and II shown below,with the corresponding data structure. Simple map M with two polygons I and II
Sushil Kulkarni 8
From the above data structure we have the following:
66.. DDaattaa mmaannaaggeemmeenntt rreeqquuiirreemmeennttss ooff GGIISS
6.1 Data modeling and representation:
GIS data can be represented in two formats:
* Vector* Raster
A. The Vector View of the World
A vector based system displays graphical data as points, lines or curves, or areas withattributes. Cartesian coordinates (i.e., x and y) and computational algorithms of thecoordinates define points in a vector system. Lines or arcs are a series of ordered points.Areas or polygons are also stored as ordered lists of points, but by making the beginningand end points the same node the shape is closed and defined. Topological models definethe connectivity of vector based systems. Vector systems are capable of very high resolution(less than or equal to .001 inch) and graphical output is similar to hand-drawn maps. Thissystem works well with azimuths, distances, and points, but it requires complex datastructures and is less compatible with remote sensing data. Vector data requires less
Sushil Kulkarni 9
computer storage space and maintaining topological relationships is easier in this system.Digital line graphs (DLG) and TIGER files are examples of vector format.
B. The Raster View of the WorldA raster-based system displays, locates, and stores graphical data by using a matrix or gridof cells. A unique reference coordinate represents each pixel either at a corner or thecentroid. In turn each cell or pixel has discrete attribute data assigned to it. Raster dataresolution is dependent on the pixel or grid size and may vary from sub-meter to manykilometers. Because these data are two-dimensional, GISs store various informations suchas forest cover, soil type, land use, wetland habitat, or other data in different layers. Layersare functionally related map features. Generally, raster data requires less processing thanvector data, but it consumes more computer storage space. Scanning remote sensors onsatellites store data in raster format. Digital terrain models (DTM) and digital elevationmodels (DEM) are examples of raster data.
Sushil Kulkarni 10
C. Graphical Comparison of Raster and Vector Systems
It is important to stress that any given real world situation can be represented in both rasterand vector modes, the choice is up to the user. Each of these systems of representation hasits advantages and disadvantages:
Method Advantages Disadvantages
Raster
§ Simple data structure§ Compatible with remotely
sensed or scanned data§ Simple spatial analysis
procedures
§ Requires greater storage space oncomputer
§ Depending on pixel size, graphical outputmay be less pleasing
§ Projection transformations are moredifficult
§ More difficult to represent topologicalrelationships
Vector
§ Requires less disk storage space§ Topological relationships are
readily§ maintained Graphical output
more closely resembles hand-drawn maps
§ More complex data structure Not ascompatible with remotely sensed data
§ Software and hardware are often moreexpensive
§ Some spatial analysis procedures may bemore difficult
Sushil Kulkarni 11
66..22 DDaattaa bbaassee mmaannaaggeemmeenntt aanndd aannaallyyssiiss
Data base management and analysis include the data characteristics and analysistechniques required for each application. Data base requirements include data acquisitioncosts, manipulation costs, data quality, data scales, and data base size. Data analysistechniques are the functional capabilities of the software and hardware, which impactsystem configurations.
Data base requirements can vary widely depending on the scope of the application; eco-system, individual refuge, state, etc. The type of data also impacts the size of the files.
GIS data undergoes various types of analysis. For example, in applications such as soilerosion studies, environmental impact studies etc.
66..33 DDaattaa IInntteeggrraattiioonn
GIS must integrate both vector and raster data from a variety of sources. Some times edgesand regions are inferred from a raster image to form a vector model, or conversely, rasterimages such as aerial photographs are used to update vector models.
66..44 DDaattaa ccaappttuurree
The spatial representations of data set are most commonly stored as either vector featuresor as raster data sets along with traditional tabular attributes. For example, an RDBMS tablecan be used to store a feature collection where each row in the table represents a feature. Ashape column in each row is used to hold the geometry or shape of the feature. The shapecolumn holding the geometry is typically one of two column types:
• A binary large object (BLOB) column type• A spatial column type
A homogenous collection of common features, each having the same spatial representation,such as a point, line, or polygon, and a common set of attribute columns is referred to as afeature class and is managed in a single table
Raster and imagery data types are managed and stored in relational tables as well. Rasterdata is typically much larger in size and requires an associated side table for storage. Duringthe storage process the software cuts the raster into smaller pieces, called "blocks," andstores them in individual rows in the separate block table.
77.. GGIISS ddaattaa ooppeerraattiioonnss
Following are the different operations used in GIS:
Sushil Kulkarni 12
A GIS consists of a data base coupled with a graphics output. There are three major typesof operations in a GIS:
1.Access methods
The user will want to access data elements with certain properties. There are threequestions involved here. The first is whether the requested data is available in the system.The second question is how long it will take to find the data. Spatial data structures poseunusual indexing problems and are a topic unto themselves Usually some variation of aquadtree (for 2D) or octree (for 3D) is used. The third question is how the user accessesthe data. The conventional query language SQL is sometimes used.
2.Analytical operations
Analytical operations allow the user to combine data to produce new data. The mostimportant operation is the overlay of different spatial data sets to produce a new data set.For example, a biologist might want to determine what variables affect the population ofdolphins. For a given part of the ocean, there may be measurements for water temperature,different fish populations, including predators (sharks), different types of pollution levels,etc. The biologist could then try to find correlations. Note that this is a multivariatevisualization problem. The analytical operations can also include computations to produce anew data set.
3. Rendering
Rendering operations show the data as some sort of map with the additional informationdisplayed. This is where Visualization techniques can be applied to GIS.
4. Interpolation
This interpolation technique is a method where a series of iterations are made over asurface to smooth it out. There are three options, which can be set for stopping theiterations whenever any one of the specified conditions is met.
§ The first option specifies the maximum number of iterations the routine should performon the map data before stopping.
§ The second option specifies the tolerance for convergence (percent of range) as apercentage of the range of elevations represented in the map. The routine will stopwhen the maximum change in any pixel is less then the specified tolerance. A value of0.5% for a map with elevations of 3,560 to 5,600 ft. equals a change of 10.2 feet orless.
Sushil Kulkarni 13
§ The third option is Convergence Tolerance (Absolute) which stops iterations when themaximum change in any pixel is less than the specified value. The value is given in mapelevation units, usually feet.
5. Class of Proximity analysis
Several classes can be developed to analysis the interest of a particular region like thedetermination of signal failure on highway, locating shortest path using shortest pathalgorithms using 2D or 3D information are the important classes of proximity analysis.
6. Raster image processing
This process is divided in to two categories:
(1) To produce new map from the existing geographical features on different map layersalgebraically using map algebra.
(2) Digital image analysis is used to detect the edges and objects. For example, detectionof roads in a satellite image of a city.