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Unit-4 -CE2O24 -Remote sensing & GIS Two Marks Questions & Answers
1. what is Gis ? tool for mapping A Geographic Information System (GIS) is a computer-based
and
on earth' GIS technology integrates analyzing things that exist and events that happen statistical analysis with the unique common database operations such as query and by maps' These abilities visualization and geographic anal'y'sis benefits offered it valuable to a wide range of distinguish GIS from other information systems and make predicting outcomes' and planning public and private enterprises for explaining events' strategies.
2.
Write the need for gis
way or another strongly linked to the Any organization, government private is in some designed in a proper manner has the geography in which it operates' A GIS that has been geographical large volumes of data of these capability of providing quick and easy access to by area or by theme to merge one data features. The user can access & select information of data' to search for particular set with another, to analyze spatial characteristics alternatives' features, to update quickly and cheaply and asses
3.
what are the components of gist
- hW)m\ - aa"
components of GIS fall into four main categories:
I) Hardwarel II) Software: II) Data:
iV)
Users:
4.what are the functions of GIs? Data Capture: Data ComPilation: Data Storage (GIS Data Models): ManiPulation: AnalYsis
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p6per that.
6,
DefineMa pscale
how the map relates to the real world features it represents.Toshow a portion of the Earth's srrface on a map, the scale must be sufficiently adjusted to cover the objective. The extent of reduction is expressedasa ratio.The unit on the left indicates distance on the map and the number on the right indicates distance on the
The Map Scale tells ihe
g
,se.
rou nd.
7. What are the different typcs of, 0T? a). Planimetric (e,9 municipd b.sc ry): A map designed to represent the horizontal positions of features; vertical inbrmdin a qilctfically ignored. gC): A map designed to portray features on b). Topographic (e.g. USGIS 75 ffi the surface of the Earth, induding relef (deyatirn), hydrography. and cultural features. c). cadastral (e.g munkiphl p.rd rT): A nEp representing boundaries of land parcels, ownership, land use, valuatixr ard dE retrd infomation. d). Image (e.g LAXIXilfT -D.$ La|tfl: A ,nap representing a remotely sensed picture or reflection of all or part of tlE Hrb grfu may or may not be orthqrErDhiiat/ dle t. e). Thematic: A map rsr 6 t 6a6u spatial relauonships and patterns among information pertaining to sdrE IIEIE c m* (e.9. income) S.Define TopograPhic m.?E
alfE dselecEd nabral and man-made features of the Earth. ? "Topography- refus b tl- $ile dule srrface, represented by contours and/or
A reference tool, showing UE
shading, but topographt m4E alsDstE, roEds and other prominent features.
g.Define Thematic Hap6 A thematic map shorvs how geographically. Thematic
{r.Hir
ad grtitative
mry rEqII' rrrd or 5p
6 pq&tin lo.What is meant by scale d ry? specific Aeographic theme, srdr
data are distributed
of a base map in order to convey
a
by state, or sales per region.
The scale of a map is the rath b.tf,een,Edaao* on the map and corresponding distances in the real world, e.9., if a rnap tus a q,re d I:50,0OO, then 1 cm on the map equals 50,000 cm or 0.5 km on the Earthl errf-'-
"Small scale" and "large scate' is often @ofilsed, e.g, 1:50,000 vs. 1:500,000
11. Defination of ceographic information system "A system of hardware, softyrare, data, people, organizations and instituUonal arrangements for collecting, storing, analfzing, and disseminating information about areas of the earth.
12. What ls meant by Hap proiections? A map projections is a method by which the curved surface of the earth is represented on a flat surfbce and it involved the use of mathematical transformations between the location of places on the earth and their projected locations on the plane.When the curved surface of the earth sholvn on a flay sheet,some distorted is inevitable.The distortion is least when the map only shows smatl areas and maximum when the map shows entire surface oFthe earth. 13.Defane UTM Proiections,
I
14. What are the names of Standard GIS Softwares? Arcview: ATCGIS is an integrated GIS consisting of three ATCGIS - the desktop software ATcSDE'- the interface For managing databases, (SDE - Spatial Database Engine) ATCIMS - software, internet-based GIS for the distribution of GIS data and services (Internet Map Server) 15,What are the different classification of maps? cadastral maps,Topograph ical maps,Thematic maps,Relief maps,Geological maps,Weather maps,Climatic maps,Political maps etc.
16,Define coordinate system. Coordinate system.can be thought as a system used to identify locations on a graph or grid .e'9 the system of assigning longitude and latitude to geographical locations is a coordinate system.There are various coordinate systems available to represent the location of any point.
17.what are the classifications of proiections?
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Conformal - local shapes are preserved Equal-Area - areas are preserved Equidistant - distance fiom a single location to all other locations are preserved Azimuthal - directions from a single location to all other locations are preserved
4
l8,What is meant bY WGS?
in cartography' geodesy' and navigation' The World Geodetic System ls a standard for use the Earth' a standard spheroidal reference It comprises a standard .ooralnutu frame for ellipsoid) for raw altitude data' and surface (the datum or iuf"'"nt"geoid) that defines the nominal sea level' a gravitational equipotential surface-(the revised in 2004), W h iC.! ]^1a,: ]/?lid The latest revision is WGS 84 (dating from ].984 and last r.i"."Jintt'a"d wcs 72' wGS 66' and wGS 60' wGS 84 is
,p","
ii"ril.i6.deu.ri"t
thereferencecoordinatesvstemuseabytheGlobalPositioninqsystem
'is
obta lle-1 conformality In polyconic proiection a near approach todirection cone' morethan. .o-ne and nt relatively small-area maps Uy projecting the area in question onto curvdd are slightly. central meridian on the map isstraight; all the- others parallel; therefore, they ar quite not curvedand irG"niiv quitepara et. simitarly, tn"'iu-ii!L "* not pieciselyperpendicular to .the meridians'
2o.Define Data base management
system(DBMs) .
with computer proorams'that A database management system (DBMS) is a software package control the creation, maintenance) and use of a database'
2l.What are the advantages in Data base
. . . . . .
reduction in data redundancy o shared rather than independent databases . ,-"Au.ui'piooiem' of inconsistencies in stored information, e.g. different addresses in different departments for the same customer maintenance of data integrity and quality data are self-documented or self-descriptive o information onlthe meaning or interpretation of the data can be stored in the database, e.g. names of items, metadata avoidance of inconsistencies o datsa must follow prescribed models, rules, standards reduced cost of softvvare development o many fundamental'operations taken care of, however DBMS software can be exp€nsive to install and maintain securityrestrictions o datatrase indudes seorrity tools to control access, particularly for writing
zz.What are the types of database sYs;tems Tvpes of database svstems
.
several models for databases: o tabular ("flat file') - data in a single table o hierarchical o network o relational
Sixteen marks Ouestions: l.Explain the Various Componenb of GIS 2.Explain tre types
of,
projections and its properties
3.What is meant by DBMS, Explain its concepts and components.
4-WriE brkfiy about process of GIS s.E)Cplain lrleasurement sca les.
6.Descdbe
the projections P"*
used in India
I- ts
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UNIT- IV GEOGRAPI{IC INT,ORMATION SYSTEM
I' what's
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rvhat is rhe purpose ora Map? spatial phenomena by graphically
conveying information about locations and attributes. "A iepresentation, norma,y to scale and on a flat medium, of a serection of materiar or absfuact features on, or in relation to, the surface of the earth.,, A spatial model ofthe real world, but differentiated from it by: abstraction, focus, symboiization. scale, projection, and purpose a). Planimetric (e.g municipal base map) A map designed to represent the horizontal positions of features; vertical information is specifically ignored. b). Topographic (e,g. USGS 7.5 minute quads) A map designed to portmy.feah[es on the surface off the Earth' F,,rh i-^r,,r.:_,_-r: ^,(elevation), including relief hydrography, and cultural feamres c). Cadastral (e.g municipal parcel map)
A map representing boundaies of land related information,
parcers, ownership, rand use, va.luation and other
d). Image (e.g LAAIDSAT image .mep,) A map representing a remotely seosed picturc or reflection of all or part of the Earth,s surface may or may not be orthomorphically
corect
e). Thematic
A map used to visrati some theme or
con""o,,".r.
1.. Visualize
2. 3.
o
ad
ffiaI
A map is a representation of expanded to areas outside ofo Maps arrow us ro
reladonstrips
paltems among information pertaining to'
the feanrres that occur
Ear*r' obviousrv' this can
be
"*;*"m'":#r;:;:*
Information
Obtain the spatial orientation and relariooships present results of analysis
Borderl part ofthe map that extends beyond
ofour
data
the neatline.
P.R.rrroo.thy,as Page
+
*
rNeatLine:thevisualframeforthatmapthatactslikeaframetosetthemapapad' part of the map that helps explain Text Information: text information is a very important
o
what the map is about. It typically includes:
o
Title: describes the general theme or purpose ofthe oReferences:providesthereaderwithinformationabouthowthemapwasputtogethef. or author, the source of the map, projections This would include information such as the map map
datums used.
.Annotation:plovidesinformationaboutindividualfeaturesonamap,suchasthenameof featffes' the states, the names ofrivers, lakes, roads, or other . Date: provides information about when the map was created' This is the central theme of the map' Map tr'igure: shows the primary figure of the map' cannot show all thd features in Inset: often shows another map, especially when the map them' For example' including Alaska and Hawaii one map space, due to the distance between tt " use of insets is to provide a frame of refer:lt" along with the contiguous states' Another and inset on our previous map could show North zoomed in portion of the map For instance' an while the map figure would show the United South America with the United States hightighted,
. o
States at a larger scale.
proper orientation of the map'
the North ArroGraticule: used as a reference to provide this does not always have to be the Most maps are oriented with north at the top' but
.
case'
easVwest orientation' Similarly, the graticule ordinarily run in a north/south'
o
Graticule:
.Legend:providesakeyiowhattheindividualsymboisonthemapmean..Thiscould indicate what the colors mean, or line symbols'
o
ground units and the map units' Scale: a visual expression of the relationship between ,r*
FRarnarnoorthy,Asst.Prof/Civil
i
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En gg
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Prye8.
brief note on GIS DATA TYPES & DATA MODELS collected and stored' Data can be described as different observations, which are or solving a problem Digitizing a Information is that data, which is useful in answering queries hours of painstaking works' but large number of maps provides a large amount of data after analysis' the data can only render useful information if it is used in
f,
Write
a
o GIS DATA TYPES:
l.AttributeData:Theattributesrefertothepropertiesofspatialentities.Theyareoften in themselves represent location referred .to as non-spatial data since they do not
spatial features' characteristics can information. This type of data describes characteristics of the is often referred to as tabular data' be quantitative and/or qualitative in natue. Attribute data
2.SpatialData:Geographicpositionreferstothelectthateachfeaturehasalocationthatmust way a coordinate system is be specified in a unique way. To specifu the position in an absolute regular square grid. For larger areas' used. For small areas, the simplest coordinate system is the
Internationally there are certain approved cartographic projections are commonly used' information is provided in maps by rnany different coordinate systems in use. This Locational
are the basic data elements ofa using Points, Lines and Polygons. These geometric descriptions the absolute and relative
map. Thus
spatial
data
describes
locationofgeographicfeatures'Thecoordinatelocationofaforestwouldbespatialdata,while crown closute' height' etc'' would the characteristics of that forest, e.g. cover group, dominant ' data' have be attribute data. Other data types, in particular image and multimedia on the specific content of the become more prevalent with changing technology' Depending photographs' animation' movies' etc'' or data, image data may be considered either spatial' e'g' attribute, e.g. sound, descriptions, narration's, etc'
o GIS DATA N{ODELS: AGlsisbasedondata,hencetherernustbeadatamodelthathastobefollorvedtostandardize procedures. TheY are:
l.
SPatial Data Models
2. Attribute Data Models
oSPATIALDATAMODEIS:Traditiooallyspatialdatahasbeenstoredandpresentedinthe evolved for storing geographic data fonn of a map. Three basic types ofsparial data models have
digitally. These are referred to as:
Pagel
P-Ramamoorthy,Asst.Prof/Civil Engg
1
-- ,& .
Raster Vector
tmage
The selection of a particular data model, vector or raster, is dependent on the source and type of data, as well as the intended use of the data. Certain analltical procedures require raster data while others are better suited to vector data.
Raster Data Formats:
A simple raster
data set is a regular grid of cells divided into rows and columns. In a
raster data set, data values for a given parameter are stored in each cell represent an elevation
in meters above sea level,
-
these values may
a land use class, a plant biomass
in grams per
square meter, and so forth. The spatial resolution of the raster data set is determined by the size
of the cell' For example, Landsat TM satellite imagery data are raster data that are corected to have a cell size of approximaiely 30 meters on a side. However, spatial resolution can be much
finer, or much coarser than 30 meters. In general, spatial resolution is
a
function oithe data
collection techniques used, and the desired outcomes. The size ofcells in a tessellated data structure is selected on the basis
ofthe
data accuracy
and the resolulion needed by the user. There is no explicit coding of geographic coordinates required since that is implicit in the layout of the cells.
P.Ramamoorthy,Asst.Prof/Civil Engg
Page
lo
3
(l4.3 )z"r.a ^a"t,
very early attempts to build GIS began from scratch, using very limited tools like operating systems and compilers. But more recently, GIS have bee, built around existing database management systems (DBMS). The DBMS handles many functions which would otherwise have
to be programmed into the GIS and
nowadays purchase
or
rease
of the DBMS is
a
major part of the system's software cost. Any DBMS makes assumptions about the data which it handles. Certain tlpes of DBMS .ue more suitable for GIS than others because their assurnptions
fit spatial.data
bener.
Two ways to use DBMS within GIS: 1.
Total DBMS solutio,: In this all d,ata are accessed through the DBMS, so
it
must
fit
the
assumptions imposed by the DBMS designer
2' Mixed solution: In this some data (usually attribute tables and relationships) are accessed through the DBMS because they fit the moder wel, while some data (usualy rocations) are accessed directly because they do
iot fit
.
the DBMS model.
GIS as a database problem: some areas of application, notably facilities management deat with very large volumes of data which often have a DBMS solution installed before the GIS is considered. Grs also adds geographical access to existing methods of search and query. Such systems require very fast response to a limited mrmber of queries ad linte analysis. Irr these areas it is often said that GIS is a "database problem" rather than m argorirtm, anarysis, data input or data display probrem. Concepts in Database Svstems:
r A database
is a collection of non-redr.urdant deta which can be shared by different application
systems. It stresses on the importance of multiple applications and data sharing.
o It implies separation of physical storage from ,se of the data by an application program, i.e. program/data independence. The user or lxogrammer or application specialist need not know the details ofhow the data are store4 such details are said to be "transparent to the user".
o Changes can be made to data without afecting olher components of the system. For e.g. * change in the format of ,rate it"ms s,ch as from real to integer, and other arithmetic operations.
t'
Changes
in the file structure such as reorgani zing
data internally
or
char.rging mode
of
access-
P.Ramamoorthy,AssLProf/Civil Engg
ll
Page
l/
{.
Relocating from one device to another, e.g. lrom optical to magnetic storage or from tape to disk.
Advantages of Database Approach:
{'
Reduction in data redundancy - the databases are shared rather than independent and this reduces problems of inconsistencies
in stored information, e.g. different
addresses in
different departments for the same customer.
*
Maintenance of dara integrjty and quAlly
'1. Data are self-documented
or
self-descriptive
-
as information on the meaning or
interpretation of the data can be stored in the database, e.g. names of items, metadata.
{.
Avoidance
of
inconsistencies making
the data follow prescribed models, rules
and
standards.
'l'
Reduced cost of software development
-
as many fundamental operations are taken care
of, however DBMS softrvare can be expensive to install and maintain.
i'
Security restrictions - database includes security tools to control access, particularly for
writing.
P.Ramamoorthy,Asst.Prof/Civil Engg
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..:----_:_:.: GIS TECHNIQUESAND DAT.A
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is a graphic representation of a portion of the earth,s surface drawn uses coiorg symbols, ar.d iabels io r€present features found on the
'rap
to scale. It
,j
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i.
ground The ideal representation woulh be realized if every feature of the area being mapped could be shown in true shape. Obviously this is impossible, ancl
an attempt to piot each feature true b sale would resrrlt in a procluct impossible to read even with the aid of a uugnifyirg glass-
'.
,
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b
The po'h'ayar oi rnany t'*at,r'es re'ufues simirar. exaggeraticn. Theref,;re, the seleciion oI feafure-s io ire sfrc,.nt as;:yell as thei: oortrayal_ is in ;1.:cciii-.i riuiiir the guidance established by the Defien_se F_{apping Agency.
A
map is a visual representation of an area a symbolic depiction highJighting relationships betr,veen elesrents of that space such as objects,
regions, and themes.
r13
dimensional. Although most cdrnmonly used to depict geography, maps , represent any space, real or imagrned, without regard to context or S..ale; e.g Brain mapping, DNA mappirrg. anLl e\rraterreskial mapping.
landownersfiip. For attributes such :rs soil type or land use (,,norninal,,variables), shaded maps that highlight regions i',polygons,') by emoloying different colors or patterns is generally *.anted. Fcr cther ath.ibuies (like
population ciersi*.._
a
"metric" variabre), a sha-ded map in r^',hich each shade corresponcls to a range of population densities is generally wanted. Thematic maps are used
to clisplay
geographical concepts such as deraih,,
distribution, relative magnitucles, gradients, spatial relatiorrships and movements. Also called geographic, special purpose, distribution, parametric, or planirneiric nraps.
ar+
"A topogrdphie map is a detailed and acanr. ate graphic representation of and na.hrral featar* on the ground_
lsa
aitural
find mineral resources, oil, and gravel deposits.AI"o, you want to know what type of rock you are buildin o" or else you might have a Leaning Tower of Pisa or a pile of rubble after a
,o:rng earthquake.
practice, of crafting
who makes maps is
4. BIO-GEOGRAPHTCAL
MAre
Scientists involved ir the sfudy shrrtr, a{ of animals, ^_:_, r plants, atlLt omer r\qlto' and other llvine living organisms ;r." u$e use maps ,-n.6- r^ :nlush'ate whqe b in tlee groups Iive or migrate. j5 It important imDortanf *n *^-_. zoologisb _- r . to many to krnw wirqe the to organisms -o--qe'r'o Lr.or that they Lltey s.,dy study hv€ live and where they move peornrc to- nple who r.,h.. monibr r endangered -^-.species need to know if the ranges ra.,.,-. of .. . ^r*._ migration have
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grazing land, ocean floors. and ocean sediments could be inciuded in this large grouping.
Meteorological maps that show climate, weather and wind are types of
environmental maps. Meteorologists, oceanographers, geographers, city planners, and many other professionals depend greatly on these maps to record and forecast their specific field.
Ei3
: :l
S,POLITICAL MAPS
Political maps show boundaries that dn,itle one po.litical entity from another, such as townships, counties, cities, and states. Some maps emphasize the boundaries by printing the areas of each political division in different colors, for example world maps usually show each country in a different cotor_
tg'
A political map can be made of any area from the local atl the way up ro the worrd level. rn generar, ,""r fewer being produced as physical
-;::tJ'o:;;:I:lX1::
maps.
9.RELIEF MAPS: Shaded Relief and Raised
l{elief
Relief maps are maps that show relief data usi ng contour Iines' colors' and/or shading to evidence thu elevation.
10. ROAD MAPS
Michelin in France
a
to encourage people to ,.rnd maps were usuarryfree charge for their
Gulf
oil in America produced
Ji"Tm;;Hll:: r7l+ wnen
maps.
.s
the first roarl maps
r'*
and oir. such
service stations began to
11
I
t
i
maPs - such as a topographic map, a Gem Trek map, Trails lllustratedmap, or DeLomte Atlas and Gazelteer _ will show ,ni_prorr"d .oudr. Some road maps specify distances between various points on the map. others
show various culfural geography features such as colleges and universities, historical sishts; and inrormation
;r;" ;;.;;;;"
1""'ms'
,1'11,"^lllinteresting.
You will .discover several publishers that have. produced maps for given regions.'Exampies include ,Michelin the
Mairs series for Germany.
chqice for two, Elain
universities.Geo
hic inJormation
investigations,.resource
technol
managemen
elyggnoe4talimpaql
assessment, urban planning,.cartoqraphy, criminology, history. sales, marketin&
-and logistics,) For example, GIS might allow emergency planners to easily calculate emergency response times in the event of a nafural disaster, GIS might be used to find wetrands that need protection from porutiory or GIS can be used by a company to site a ne' business ,ocation to take advantage of a previously underserved market.
Gta .-
f
D al
E. W. Gilbert,s version (195g) of John Snow,s 1g55 map
I
of the Soho cholera outbreak showing the clusters o{ cholera cases in the London epidemic of 1g54 l4il,rile the basic elements of topology
and theme existed previously in cartography, the John Snow nrap was unique, usjng cartographic methods rrot
only to depict but also
to
analyze clusters
of
geographically dependent
phenomena for the first time. The early 20th century saw the development of ,,photo lithography,, where maps \dere separated into layers. Computer
hardware development spurred by
l I
l
i I I
i
I
l
[itl: ll
rl. .:i
rating classification factor was ajso added to permit analysis. CGIS ',rras the t,r,orldls first ,,s;rsts11,, anrl ,azas
arr irr,proverneni over
"::rapoing" appiications as ii orovjcred capabiiities foi: o..terra,y',measurerarnr., arrii oigitizing/Scanning' It supported a national coordi,ate system that spanned the conii.ent, coded lines as "arcs" rraving a true embedcred toporogy, and it stored tire aiiribute and locationar in{ormation in separate f es. As a resuit of ihis, Tom'linson has become known as trre "father oI GIg" particulariy for his use of overlays in promoting the spatial analysis of convergent geograpfuc data. CG1S
lasted into the 1990s and built the rargest digitar .rantl resource database in Canada lt was deveroped as a mairframe based system in support of federar a,rd Pl0vincial rgqource pranning and management. its strength was
;l
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.
6D a-r
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analysis of comprex data sets The CGIS was never avairabre in a commercial form.
In
7964,
Howard T Fislrer formed the Labordtoryfor Computer Craphics and spariar Anarysis at the Harvard Gracruate schoor of Design (LCGSA 1g651991), wher.e a number of ir rvere deveropecr,
""d
*hi.i:;;T:
ffi ::':ffi;, j#,:Jl:l:]o:
and systems, such as,syMAp,, ,GRID',
and,oDyssEy _;;;r";;';";r".r; and inspirational sources ror. subsequent commercial ,"r";.;;;-
__";
universities, research centers, and corporations worldrvide.
M&s Compuring (tater rntergraph), Environmental Ir"rl^:1lr.re80s, j:t::_:"":.h rasritute (ESRr) and cARrs Com;;;;';'""*.e
::::::;:,:::l'
l*u:s"a successfuliy incorporating many
sencrafi^n
:::i:: .,
T*"*
as commercia, Dvrtware/ ;;,t, """***; of the cGIS feafurs, combining
to separation of spariar and anribute
F.
t. l,'
;#on;,
{tdra rnto databasq+'trucfureii. ih rrarallel ,r.- j1.^r^--., - - " -'o -'urvurE of a publc doinain GIS was *""
,lt 4''", c.;a "r -u"s".*i,i ;;"; I. L"
the first
need
of the United
beg_un eeryn
;
States
military for softr*,are i". envircnmental planningThe larcr 19g0s and 1g0s
spurred on by the growing use of CIS on lJnix rvor.j computer. By the end of t centur/. the rapid had beer.r consoridated
-.1"'* werebegi*inr,oor*'jlH:f
iii u
t4SZ b, tli.H82 bv tlte
O"O"^r"rr.*;;;:; industry growth
wer.e
ffiT"T:::::;:"j'
:r".:,.'_'::":t"t:;,:,::,:ff
requiring data format and h-ansfo. ci_-,J^_r number or r,"",
op*;;:T,:;":::#
there is a growing
_".-trv. n{urge
systems and can be customized to perform specifi.,uru".
----/
a. a3
J:J:;
of operating
.nl
/
alt'r'r[ c''n?s"'o'']s AdrEuqri,o \/
*f
619
2
Mo-XfJu'rw-eo14
/ CoMPONENTS OF A GrS 1A CIS can be divided into tive components: \ Ieople, Data, Hardware, S=Ho ancl Pjgcgdy.fH...All of these componenrs need to be in balance for the system to be successful. No one part can r-un without the other.
PEOPLE
The people are the component who actually makes the GIS. work. They include a plethora of positions including GIS managers, database administrators, application specialists, systems analysts, and programmers. They are responsible
for maintenance of the geographic ,latabase and provide technical support.
i..,
:.r,
.,j::,
professional s3-rr'&Es, and gaki::g degisions. They irclui{e
lesource rnanag'ert planners, enfre
t-.rl..u
e
sllgirlllg
lecilitv managers, engineers, iawl,ers, L-.!rsin,_,ss-
rs. et(:.
GIS speciaiists ale the people w-ho make thc GIS v;ork. They include GIS managers, database
adminis
,
E sJrtg*l ur*-l),stl u"d for the rnaintenance of ihe geographic
Spplglgry
Progranlmers. They a.re responsible
database ancl the provision of technical support to the other two classes of users.
(Lo,7002)
a^eq
,ri. L-"-
.
Fi.
{snli::
p.lr, -*:a
i!,'
:I:
PROCEDURES Procedures include how the rh^ data ,.r^.^ stored, managea, nu.,rro.,
will
nalyzed'''"d
The procedures
,r" ,n" ,**"0'l rhe abi,*y or a Grs ," wha
be retrie
fi"'x;
;:::j::T::jr"fir:
#jI;j;X;::."T::T:""*
f differentiates this type of system from a", The transformadon
coordinare system, setting set' and converting data
i I F
li t: i
c 4r-
u".",or,.a r,
"rn*,*.t-",,1, ;;;1r*r
iffi::l ::H#
fiom yector to raster
to
j_:,.:T::TTri:;
or raster to vector. (Carver,
lgg').
The producers and the main products of GIS Software are the follo,,ving: n_1, Environmental Sysierns Research Institute ( ESRI Arclnfo, ArcView. ):
., . 1 Autodesk: 2. ^, , .
3.
AutoCAD
N4ap
Clark Labs: IDRISI
4. International Institute for 5. Mapinfo Corporation: ,.j;.*-" 6. Bentley Systems: Microstation. 7. PCI Geomatics; pAMAp
turvey
ancr
Earth sciences: ILWIS
B. TYDAC Inc, : SPANS DATA Perhaps the most time consuming ancl costly aspect of initiating a GIS is creating a database. There are several
things to corsider befc
:"", l :::::
is cruciar to check the qualit-y of the set;an add many unpteasant and
data;:;::;:t.T,T:i:
costl;r,r"rr.
GIS
.r_i,";";;;'"; will
be
Attribute Accuracy _ An attribute is a fact about some location, set of locations' or
l.l ;:l
i'
i.
,
feafures on the srirface of the earth. This infornration ,-.ite:: i;i:r:;.i.. measurements of some sort, such as temperafure or ele'ation or a lairi r,i a piacr name. The source of errorr usually lies within the collection of ihese:acts, It is ..:a^t , ,, v rtd{ i'.: ,ne rnalysis a
aa6
that
The conversion or abstraction of the earth and it,l defines locarion and properries of indivicruar ,.u*.oooto,o.,il::1.4
Definition
about
,
database
2:
Duplicating the real world i,", rh- ^^*-
things,",
;;
;;":#; :l:;:;0,".
a?-
bv core*ins information
:
!!-ci-n!enfl1- B.e-g-{ Iggg"tce !f,.youshqs,.,e_tg keep it up to date. rtial Data = Sphial (Where) + Dara (I/\hat)
a
r
" '-;-;
NON-fl'ATIAL I
-
DATAS
\n-spatiar
t1"'r'.4'-4 Pi$"'iL'i '-'r#"-1 t,'-( :-l' :t iv.:#<}t
dara may be loiiJa
,t g."."0"0'ir""s wirh marching a*ribures
and displayed, as regr:lar maps. This is common
in
Geographic Information
Systems (CfS).JFor example census information ....vrrrrq,urr such uucn as race . / data, can be displayed as maps.
1",.":n,
or income,
non-
UnJerumatdy fton_spatial data
"Ortal
SPATIAT ANALYSIS WITH GIS
Civen the vast range of spatiai analysis tecliniques that have
been
developed over the past half century, an)/ summary o. ..rri"* .r;;"r;;;;;; subje'ct to a limited depth' This is a rapidry changing fierd, and GIS packages are increasingry incruding anaryticar toors as standard bu,t-in fac,ities or as optionar tool"rtr' add-ins or 'anarysts'' In many instances such fac,ities are providecr b,v the oriqinal software suppliers (commercial vendors or collaboratrve non cwrmercial development tearns), -"vhiist in i:ther
.rr", ,".r;;;t;;
c ag.-
developed and are provide
software deveropment
o'
ur,'
support, scrip ting r".,,, o"r'^
t,t
-
parties' Furtherrr
'n"o
o"oo'
l"'
;;;
t,:I}"j:tJ
t"r;
""r'
r',o
xmfu**":*ffi.:#[!*;; srve
guide to the subject.
LINE SEGMENTS
In geomehy, ? ljne sesrrro-+ ;^ ^
_
;iil"T;:ii,:::::f ff '' rvq" Iil;":TiI1*;:'T.:]*;:#.f of line segmer urr me Irn€ between its end points,
Examples
generauy,when the
::,n*
l
edge (of
ooo of a biangre or
square.-rr4orb
;ilffJ*;x,x:i:Til"T"J:,."T:J;
When the end points both lie on a cutve such as a circle, a chord (of that a Iine segment
.*r".-."n is ca.lled
.
""a r",l:,:1']::'
.'nu
curve).
E w. rr a plane
figure that is bounded by
I"h:"#:;. ;":;::,'1"' ;?1-- ;ii: - ' -- -r' y "', ;H'ff us u arr two Usually Evo
is
not strarght
or c'rneis rhe in'ferior
o
;r
rumoer of dimensions. r'-o''
oo"t meedng *'^l:.'"* edg, " at a corner e rr
".''
are re
-"' ;.*";;.T;#.:;::X;TJ1 segments
ourrrl, \ - // v'rt(:r wls9 the ling
single e.tge. ' singreetrge''herwise
*"
'rrt6re tni
' -'- 'rotion has been adapbd -ur in V?flous ^.v. l'urPoses ways to suit particular For example in thu ffi'. ".,,'.-._._-.-wu 1. generafion) field' oi"" o'.u slightly the Hi,*," rt up" is srored rerated ro rhe u.,, .,ranipurated way ffi-,itru
S.;,
orrr..nl,
Hpin
ffi:l ffir) kA,
ffi*
ffi ffi'
ff*,.
t-
l'L:,-*t'eaptu"" altered;";*"'"
_,"";";;;rrr".lore
4
DATA REPRESENTATION real world objects (roads, rand use, erevation) r'irh into hvo abstractions: discrete obje*s (a r,o,,"; 1!(5. (ra1n fall amount or ele'ation). trvo broad methods Th--r-e are -^ ,rr., to store used ",__^',ciata in a GIS for both abstractions: Raster !,ector. anil
o,n,r,lll"'ot"j":*:**
u.,loJl1;?:::;;[ffi.
VECTOR
A simple vectc
,"r,;;r'J#:.:i:1":'""
rines ror rivers,
In a GIg
vector eremenrs: points ror wers.
geographical features are oft
considering those featL are expressed
o,
0o,".;,
;.ffi,.,nJ:
;orilHT:;ff-r".":,
POINTS Zero-dimensiona be expresseti
o,
;;,'"p;fi;:""."ir;:,.r:,phical ^
reature,s rrrar can best
words' simple Iocation example, the loca For h.ons of u'ells, peak e.revafions; feah of interest or trailheads' iroints convey the "" ]east a L'i iiLarmant"t or *t"' be rrsed to ."p."r".,, ur"u,*ouni a iriap of the worrd nleasuremenrs
"." ._-i,rqEs oR
ilisplal'ed
", "
*,or]*""
r.r,,0,":':;..fi.l,;:*:'
"rr";:":"J::::#::::::
pcints rather ihan porl,goi.rs. rJo
POLYLXNES
I
.
One-dimensionai
rinear rea'[ures such
ff:}:}H*;:i:'::'H:'##:1'' u,l ffi i,:: i.'.#:,f ffi
rea tu
res,u,u..,n u,,
:
3o
rlr
as
"l::, ::-T
LYGONS
Two-dimensional
polygons are ,so,-{ r^used for geographical features that cover particular area of ."" the uu.r] a boundaries, 0,,,,,,*;. incrude rakes, park
l
;; ;;::"T
:;::::::may
uses. r,orygons amounr of irLformafion convey rhe most of the .e file types. ,,::: polygo, ;^,,",," feafures can measure perimeter and a.rea.
-
coloured depending on level
" Beomgqyl that are within r tugh ley..et of polturion.
,;;;
,,.
. ,,t-*'"
'-.. "u
qsE(r
to rdentj
(1'6 km) of a lake (polygon g
,
E a
?.:.
:.
.
:',rr,,""*,^;,,,J; '
:
. Vector features
through il"::*:: r",rr*;T:,.1_,:::T,, must not overlap'.
the
can also be used to .epresent vector daia continuously vary and tuiangurareo """-,:-::;1t"ns ing phenome,a. Contour o."rriJ"ll, lines oiher to represenr
conrin,*r";:;r"
*;::1ff1.:; ",","*; ". -, **" ;: varues at point iocations, which .- ._-
are connected by Iines to forr,, rriangtes
*o*r.",,n",";t
mesh of biangtes. an"
l;;_,**lar
,u.. or-*"
VECTOR
A raster data fpe ig in esser,". u.t, . --.. rype of digitar irnage. iar wirh 0,r,", Anyone who is on"#i"u"tt recognize -- 'Lrl,Bruze the vidual tr,e pixel iduar unit p;rei as the sma]les unir of an image. imase A , these.exers wir nct,frsm ,n.".,-.*"n, ^ creare an
", ;" ,;;r,
-^:,.-l
;;;I::":1r
vector modet. tr{&ire a cligirar image
im4ge
,, ;;;;
o3r
1",,n ,n" outpur
as
a discrete vaiue,
ora e-xien.1eo 6_1. uSing raster bands co.iormaps ia mapping behveen a
coiors,
:-a;^-.. ..--ri. .i,., ranie rr.itlr onc ro!\ lor p.trlt unique teli :asrer Cata set is its cell width in gro.,r",.l ,.,it . Raster data is stored in variorrs
j:i:..!.::.
The resolution
formats; from
a standard binary Iarr,,c objecr (BLOB) data si,:_:.,!: -::r.-: rrlanagem_ent systern (RDBIV{S) similar :.-,^._
ol TIF, JpEG, eic.
tcr
tr
p3? I: :
oi thr
..
lacl ):um*4"1)
are advantages and disa
a
using a .raster or vector. data
rnuitituije of :, ,i..
much :.Smaller.
ritr
storage
data can
and marnraine.
.,; ,ll ]"llj,]r,rr,,:: rne fraster image will have to ho -^*_r^, ";;;;
;j;#,;:::#,
,"",,,;:;;il;JJ.:,;::;H:,_"::,:"J::j:H::,;.::,::; ,
anarysis capabirity esf".ialry
;. as roads, .:1r1"::l]::-:.n:*" porver, rair, te]ecommunications,
t:"
etc- For
ex
,,ne6a6,1,,, for sucl '"' rterworKs" ,,..1.,
characterisrics
or roads. 0..,", A::::::: duuws tyst to query for the best route .1r hdll.^ r r _ ""0'1*;:l;,"j:::
Lne
j;,;.,'-::;"::*'J:X;'H::;
;:,,':1:::T';"';;"'..""
es and a conaecting road
ls at least hro lane highrt-a., ie,featu,*..;r;l--;-- ,-, -.-'.. i{'.'5f'!'-"I:qeftry+
a3:
,,', ''":: ',.'...: ",'::,'-
