lecture 12 basic spatial analysis p1

7/25/2019 Lecture 12 Basic Spatial Analysis P1

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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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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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(tools), such as:

Measurement

Queries & Selection

>eclassification

7ufferinO%erla$

"etwor5 Anal$sis


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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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(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(

?rom ArcGIS 1/ Welp


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Geometric Inter%al


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(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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(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$

lecture 12 basic spatial analysis p1

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