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Announcements
Data
Map of OronoE911 road file for Orono
Tax maps for Orono
Questionaire results
Source
Maine Office of GIS
Maine Office of GIS
Town Office need to
diiti!e
"eed to collect #$
inter%iews
Due next T&ursda$
Data Sources a list of data files and t&eir sources' e((
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) Test 1co%erin c&apters 1*+ and la#s 1*,
"o class on Tuesda$- Oct( ./t&(
Test will #e emailed to all students Sunda$
0Oct( 1+t&- on or #efore 23// 4M
T&e test is open #oo5- open notes(
T&e test s&ould #e emailed #ac5 to me #$
midni&t- Oct( .1st(
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6ecture 1.
7asic Spatial Anal$sis
8&( 9 4art 1
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Spatial data anal$sis
Input * spatial operation* output
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Input Scope
6ocal :point; to :point;
"eior&ood
ad
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Spatial data anal$sis
Usually involves manipulations or calculation of
coordinates or attribute variables with a various operators
(tools), such as:
Measurement
Queries = Selection
>eclassification
7ufferinO%erla$
"etwor5 Anal$sis
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?iure @(1 >aster GIS measurements3 0a 4$t&aorean distance- 0# Man&attan
distance- 0c proximit$ distances and 0d perimeter and area
7.53244 22
11 ==+=BA
2351212723 =+++++++=P
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?iure @(1 >aster GIS measurements3 0a 4$t&aorean distance- 0# Man&attan
distance- 0c proximit$ distances and 0d perimeter and area
7.53244 22
11 ==+=BA
2846126*
2351212723
=+++==
=+++++++=
wlA
P
., B,
., ..
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?iure @(B Cector GIS measurements3 0a distance and 0# area
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Spatial data anal$sis
Usually involves manipulations or calculation of
coordinates or attribute variables with a various operators
(tools), such as:
Measurement
Queries & Selection
>eclassification
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Quer$
) A uestion to t&e data#ase(
) T&e data#ase response is a ta#le(
) T&e ArcGIS data#ase response isselected records( If t&e ta#le is t&e feature
ta#le it also displa$s t&e selection on t&e
map(
) Selected records can #e exported to form
a new s&apefilefeature class(
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T&eme "ame
SQ6
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Set Ale#ra
) Selection 8onditions ma$ #e formali!ed usin
set ale#ra3
S$m#ols3
Ma$ #e applied alone or in com#ination to select
features(
= ,,,,,
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?ield "ames
) T&e ?ield list in t&is dialo automaticall$ listsfields wit& t&e appropriate delimiters for t&e t$peof data $ou are uer$in3
) If $ou are uer$in data in a file eodata#ase-s&apefile- d7ase ta#le- co%erae- I"?O ta#le-t&en field names are enclosed in dou#le uotes3
FA>EA:) If $ou are uer$in data in a personal
eodata#ase t&en field names are enclosed insuare #rac5ets3
A>EAH
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Strins
) Strins must alwa$s #e enclosed wit&in sinle uotes( ?or example3
) FSTATE"AMEF J K8aliforniaK
) Strins in expressions are case sensiti%e- except w&en $ou areuer$in personal eodata#ase feature classes and ta#les( To ma5ea case insensiti%e searc& in ot&er data formats- $ou can use a SQ6function to con%ert all %alues to t&e same case( ?or file*#ased datasources- use eit&er t&e L44E> or 6OE> function(
) ?or example- t&e followin expression will select customers w&oselast name is stored as eit&er Nones or NO"ES3
) L44E>0F6AST"AMEF J KNO"ESK
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Strins
) Lse t&e 6IE operator 0instead of t&e J operator to #uild a partialstrin searc&( ?or example- t&is expression would select Mississippiand Missouri amon t&e LSA state names3
) FSTATE"AMEF 6IE KMissPK
) ou can use reater t&an 0- less t&an 0R- reater t&an or eual 0J-less t&an or eual 0RJ and 7ETEE" operators to select strin%alues #ased on sortin order( ?or example- t&is expression will selectall t&e cities in a co%erae wit& names startin wit& t&e letters M to 3
) F8IT"AMEF J KMK
) T&e not eual 0R operator can also #e used w&en uer$in strins(
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Strins
) ildcard 8&aracters
) A wildcard c&aracter is a special s$m#ol t&at stands for one or more c&aracters(
) ?or an$ file*#ased data- KPK means t&at an$t&in is accepta#le in its place3 onec&aracter- a &undred c&aracters- or no c&aracter( Alternati%el$- if $ou want to searc&
wit& a wildcard t&at represents one c&aracter- use KK(
) ?or example- t&is expression would select an$ name startin wit& t&e letters 8at&- suc&as 8at&$- 8at&erine- and 8at&erine Smit&3
) F"AMEF 6IE K8at&PK
) 7ut t&is expression would find 8at&erine Smit& and at&erine Smit&3) FO"E>"AMEF 6IE Kat&erine smit&K
) T&e wildcards $ou use to uer$ personal eodata#ases are KK for an$ num#er ofc&aracters and KK for one c&aracter(
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6IE
ildcards
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T&e "L66 e$word
) "ull %alues are supported in fields for eodata#ases and for data fieldsin s&apefilesd7ASE ta#les and co%eraesI"?O ta#les( If $ou select afield of a t$pe t&at supports null %alues- and if t&at field contains an$ null%alues in t&e records displa$ed #$ t&e Lniue Calues list- $ouKll see a"L66 5e$word at t&e top of t&e Lniue Calues list( ou can dou#le*clic5t&e "L66 5e$word to add it into $our expression- w&ere $ou can use t&e
IS operator to uer$ t&e field to select all its null %alues3
) F4O4L6ATIO"9@F IS "L66
) or IS "OT to select all its %alues t&at arenKt null3
) F4O4L6ATIO"9@F IS "OT "L66
) T&e "L66 5e$word is alwa$s preceded #$ IS or IS "OT(
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IS 5e$word
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Quer$in "um#ers
) ou can uer$ num#ers usin t&e eual
0J- not eual 0R- reater t&an 0- less
t&an 0R- reater t&an or eual 0J- and
less t&an or eual 0RJ operators(
) F4O4L6ATIO"9@F J 2///
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8alculations
) 8alculations can #e included in ueries usin t&ese arit&metic operators3 U*
) 8alculations can #e #etween fields and num#ers(
) ?or example3
) FA>EAF J F4E>IMETE>F 1//
) 8alculations can also #e performed #etween fields(
) ?or example- to find t&e countries wit& a population densit$ of less t&an oreual to .2 people per suare mile- $ou could use t&is expression3
) F4O4199/F FA>EAF RJ .2
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Operator 4recedence
) Expressions e%aluate accordin to standard operator precedencerules( ?or example- t&e part of an expression enclosed inparent&eses is e%aluated #efore t&e part t&at isnVt enclosed(
) T&is example3
) WOLSEWO6DS MA6ES 4O49/SQMI U A>EA
) e%aluates differentl$ from3) WOLSEWO6DS MA6ES 04O49/SQMI U A>EA
) ou can eit&er clic5 to add parent&eses and t&en enter t&eexpression $ou want to enclose- or &i&li&t t&e existin expressiont&at $ou want to enclose and t&en press t&e 4arent&eses #utton toenclose it(
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8om#inin Expressions
) Expressions can #e com#ined toet&er wit& t&e A"D and O> operators(
) A>EA 12// A"D GA>AGE ,
) &en $ou use t&e O> operator- at least one expression of t&e two
expressions separated #$ t&e O> operator must #e true for t&e record to #eselected(
) >AI"?A66 R ./ O> S6O4E ,2
) Lse t&e "OT operator at t&e #einnin of an expression to find features or
records t&at donKt matc& t&e specified expression( "OT expressions can #ecom#ined wit& A"D and O>(
) SL7>EGIO" J K"ew EnlandK A"D "OT STATE"AME J KMaineK
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Spatial Selection 0Select #$ 6ocationIdentif$in features #ased on spatial criteria
Ad
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Ad
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Touc& t&e #oundar$ of
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S&are a line sement wit&
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Spatial SelectionIdentif$in features #ased on spatial criteria
Ad
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Selection #ased
on spatial andnon*spatial
attri#utes
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Spatial data anal$sis
Usually involves manipulations or calculation of
coordinates or attribute variables with a various operators
(tools), such as:
Measurement
Queries = Selection
Reclassification7ufferin
O%erla$
"etwor5 Anal$sis
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Example34arcels
>eclassified
7$ si!e
Spatial data
anal$sis3>eclassification
An assinment of a class
or %alue #ased on t&eattri#utes or eorap&$ of
an o#
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Spatial data anal$sis3>eclassification
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>eclassif$ in ArcGIS
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"atural 7rea5s 0Nen5s
)"atural 7rea5s classes are #ased on natural roupinsin&erent in t&e data()8lass #rea5s are identified t&at #est roup similar
%alues and t&at maximi!e t&e differences #etween
classes()T&e features are di%ided into classes w&ose #oundaries
are set w&ere t&ere are relati%el$ #i differences in t&e
data %alues()"atural #rea5s are data*specific classifications and not
useful for comparin multiple maps #uilt from different
underl$in information(
?rom ArcGIS 1/ Welp
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"atural 7rea5s
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Eual Inter%al
) Eual inter%al di%ides t&e rane of attri#ute %alues intoeual*si!ed su#ranes(
) T&is allows $ou to specif$ t&e num#er of inter%als- andArcGIS will automaticall$ determine t&e class #rea5s#ased on t&e %alue rane( ?or example- if $ou specif$t&ree classes for a field w&ose %alues rane from / to,//- ArcGIS will create t&ree classes wit& ranes of /1//- 1/1.//- and ./1,//(
) Eual inter%al is #est applied to familiar data ranes-suc& as percentaes and temperature(
) T&is met&od emp&asi!es t&e amount of an attri#ute%alue relati%e to ot&er %alues( ?or example- it will s&owt&at a store is part of t&e roup of stores t&at ma5e upt&e top one*t&ird of all sales(
?rom ArcGIS 1/ Welp
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Eual Inter%al
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Quantile
) Eac& class contains an eual num#er of
features(
) A uantile classification is well suited to
linearl$ distri#uted data(
) Quantile assins t&e same num#er of data
%alues to eac& class(
) T&ere are no empt$ classes or classes
wit& too few or too man$ %alues(
?rom ArcGIS 1/ Welp
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Quantile
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Standard De%iation
) T&e Standard de%iation classification met&ods&ows $ou &ow muc& a featureKs attri#ute %alue%aries from t&e mean(
)ArcMap calculates t&e mean and standardde%iation( 8lass #rea5s are created wit& eual%alue ranes t&at are a proportion of t&estandard de%iationXusuall$ at inter%als of 1-Y-Z- or [ standard de%iations usin mean %aluesand t&e standard de%iations from t&e mean(
) A two*color ramp &elps emp&asi!e %alues a#o%et&e mean and %alues #elow t&e mean(
?rom ArcGIS 1/ Welp
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Standard De%iation
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Geometric Inter%al
) T&e eometrical inter%al classification sc&eme creates class#rea5s #ased on class inter%als t&at &a%e a eometricalseries( T&e eometrical coefficient in t&is classifier canc&ane once 0to its in%erse to optimi!e t&e class ranes(
) T&e alorit&m creates eometrical inter%als #$ minimi!in
t&e suare sum of elements per class( T&is ensures t&ateac& class rane &as approximatel$ t&e same num#er of%alues wit& eac& class and t&at t&e c&ane #etweeninter%als is fairl$ consistent(
) T&is alorit&m was specificall$ desined to accommodate
continuous data( It produces a result t&at is %isuall$appealin and cartorap&icall$ compre&ensi%e( It minimi!es%ariance wit&in classes and can e%en wor5 reasona#l$ wellon data t&at is not normall$ distri#uted(
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Geometric Inter%al
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Spatial data anal$sis
Usually involves manipulations or calculation of
coordinates or attribute variables with a various operators
(tools), such as:
Measurement
Queries = Selection
>eclassificationBuffering
O%erla$
"etwor5 Anal$sis
7 ff i d t& 4 i it ? ti
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7ufferin and ot&er 4roximit$ ?unctions
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Mec&anics of 4oint and 6ine 7ufferin
7 ff i C i t i t # ff l
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7ufferin Cariants3 point #uffer examples
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>eions in 7ufferin inside- outside- enclosed
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Spatial data anal$sis
Usually involves manipulations or calculation of
coordinates or attribute variables with a various operators
(tools), such as:
Measurement
Queries = Selection
>eclassification
7ufferin
Overlay
"etwor5 Anal$sis
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O%erla$
8om#ination of different
data la$ers
7ot& spatial and attri#utedata is com#ined
>euires t&at data la$ersuse a common coordinate
s$stem
A new data la$er is created
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Vector Overlay
)Topolo$ is li5el$ to #e different)Cector o%erla$s often identif$ line intersection points
automaticall$(
)Intersectin lines are split and a node placed at t&eintersection point)Topolo$ must #e recreated for later processin
An$ t$pe of %ector ma$ #e o%erlain wit& an$ ot&er t$pe
Output t$picall$ ta5es t&e lowest dimension of t&e inputs
For example: Point on Polygon results in a point
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Am#iuous
result
Ln*
am#iuousresult
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Vector verlay0common wa$s applied
)86I4)I"TE>SE8TIO")L"IO"
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86I4
)8oo5ie cutter approac&)7oundin pol$on defines t&e clipped second
la$er)"eit&er t&e #oundin pol$on attri#utes nor
eorap&ic 0spatial data are included in t&e
output la$er
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I"TE>SE8TIO"
)8om#ines data from #ot& la$ers #ut onl$ for t&e
#oundin area
(!ounding polygon also defines the output layer"ata from both layers are combined
"ata outside the bounding layer (#stlayer) is
discarded)
)Order of intersection is important
($ to ! or ! to $)
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L"IO"
)Includes all data from #ot& t&e #oundin and
data la$ers
)"ew pol$ons are formed #$ t&e
com#inations of t&e coordinate data from
eac& la$er
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%hy do buffering and vector overlay often ta&e
so long'
!ecause a time consuming line intersection test
must be performed for all lines in the data layers
hen, inside vs outside regions must beidentified for all new polygons
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n n g t e n t e r o r: s a p o n t n s e a p o y g o n
P o t e n t ia l p o in t
A lg o r i t h m :
c o u n t l in e c ro s s in g s t o o u t s id e o f c o n v e x h u l l, i f t h e y is a n o d d n u m b e r t h e p o in t is in s id e , i f e v e n n u m b e r, p o in t o u t s id e
n = 2 , o u t
n = , o u t
n = ! , in
n = " , in
Alorit&m3
4ic5 a direction
(*ast (right) in the example)8ount line crossins to t&e
outside of con%ex &ull (shadedpolygon)
If odd num#er t&en t&e point is
inside
If e%en- t&e point is outside
?indin t&e interior3 Is a point inside a pol$on (shaded)
4otential point
Vector verlay
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Vector verlay
8ommon features in Cector o%erla$s create
:Sli%ers; or :Sli%er pol$ons;
A common feature in #ot& la$ers( T&e pro#lem is
t&at eac& definition is %er$ su#tl$ different (different
time, source, materials)so t&e pol$ons donVt line up(T&e$ can onl$ #e seen a %er$ lare displa$ scale
#ut can represent o%er &alf t&e output pol$ons(
T&e$ ta5e %er$ little space #ut affect anal$tical
results(
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Methods to reduce/remove slivers:)>edefine t&e common #oundaries wit&
&i&est coordinate accurac$ and replace
t&em in all la$ers #efore o%erla$
)Manuall$ identif$ and remo%e
)Lse snap distance durin o%erla$