Chapter 10
Joins and Overlay
Mastering ArcGIS Pro�Second Edition
Maribeth H. Price
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No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.
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Intro to GIS
Lesson 10: Joins
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What are joins and overlay?
Source: South Dakota Geological Survey
One primary use of G I S is to combine layers of information
Both join and overlay combine the data tables from two sources but differ in treating overlapping features
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Reviewing a table join
Source: Esri
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Spatial joins
In a spatial join, the records are matched using a spatial relationship instead of a key field
The target feature class is copied to a new data set that contains the combined tables
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Spatial join using intersect
Source: City of Austin
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Spatial join using proximity
Source: Esri
Cities is the target layer, so a new feature class of cities is created (a)
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Spatial join using containment
Source: City of Austin
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Comparison of operators
Source: City of Austin
In this example, the intersect and within operators give nearly the same result
They would only differ if a septic landed on a boundary
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Cardinality and spatial joins
Source: Esri
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Managing cardinality
Spatial joins come in two types to offer options for handling a one-to-many cardinality
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Join types
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Cardinality of parcels and zones
Source: City of Austin
In the parcels and zones example, parcels usually lie within a single zone, so the expected cardinality is many to one
A parcel in two zones would be an exception or a logical consistency error
A one to one join works well and no merge rules are needed because only one zoning record is expected to match each parcel
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Cardinality of cities and airports
Source: Esri
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Cardinality of septics and geology
Source: City of Austin
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Cardinality of highways and soils
Source: USGS, Esri
You wish to determine the soil characteristics for each highway to help plan maintenance schedules (some soils degrade roads more quickly)
Each highway is expected to cross multiple soil units, so a one-to-many cardinality is expected
A one to many join type would create multiple copies of each highway to match every soil unit it crosses, which is not very helpful
A one to one join type with merge rules works well for this problem
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Merge rules for a one to one join
Source: USGS, Esri
The Join_Count field indicates how many soil units matched each highway
Numeric fields can have statistical merge rules like Mean or Sum
Text or categorical fields cannot use statistical rules
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Classic overlay 1
Source: South Dakota Geological Survey
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Classic overlay 2
Source: South Dakota Geological Survey
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Types of overlay
Intersect only keeps the areas that overlap
Union keeps all areas from both inputs, whether they overlap or not
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Union example 1
Source: USGS, Black Hills National Forest
In union, the usual goal is to combine all the data and the extent of the data sets is typically the same
The combined table can be queried (pink) for combinations of values that are susceptible to geologic hazards
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Union example 2
Source: USGS, South Dakota Geological Survey, Black Hills National Forest
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Intersection and geometry
Source: USGS, City of Austin
Union can only be performed with two polygon inputs
Intersection can be applied to all geometry types
a) A line-in-polygon intersection can assign geologic unit information to streams
b) A point-in-polygon intersection can assign school district information to houses for sale
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Intersection output geometries
Different output geometries may be chosen depending on the input
The output geometry cannot be higher than the highest input geometry type
a) Intersecting two polygon layers can yield polygons, lines, or points
b) Intersecting two line layers can produce lines or points
c) Intersecting lines and polygons can yield lines or points
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Comparing extraction and overlay
Although the spatial output of intersect and clip look similar, they are not the same
In extraction functions
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Data quality in spatial analysis
Source: Esri
Data quality can significantly impact the results of a spatial analysis
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Using an XY tolerance
Source: Esri
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Areas and lengths
Source: South Dakota Geological Survey
Source: Esri
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Setting up a spatial join
Stepping through this series of questions can help you determine how to set up a join
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Setting up a join 1
Source: Esri
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Setting up a join 2
Source: Esri
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The join result
Source: Esri
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No reproduction or further distribution permitted without the prior written consent of McGraw Hill, LLC.
Because learning changes everything.®
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Accessibility Content: Text Alternatives for Images
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What are joins and overlay? - Text Alternative
The three maps of South Dakota show different information. All three maps lay horizontally one after the other. The first map is labeled 'Slope class' consisting of blue gradients. The second map is labeled competence consisting of yellow gradients. The third map is an overlay of competence and 'Slope class' which appears to be a collage of the first two maps.
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Reviewing a table join - Text Alternative
The first table titled US states is the target table which consists of four columns and seven rows. The data given in the table are as follows: Column 1, OBJ: 1, 2, 3, 4, 5, 6. Column 2, Shape: Polygon, Polygon, Polygon, Polygon, Polygon, and Polygon. Column 3, NAME: Hawaii, Washington, Montana, Maine, North Dakota, South Dakota. Column 4, STATE underscore FIPS: 15, 53, 30, 23, 38, and 46. The second table titled Pop data is the join table which consists of four columns and seven rows. The data given in the table are as follows: Column 1, STATE underscore FIPS: 13, 15, 16, 17, 18, and 19. Column 2, POP 2000: 8186453, 1211537. The other data in the column is not visible as a box reading ‘Join tables on common field’ is present. Column 3, POP2010: 10014045, 1309580, 1581697, 13089726, 6479832, 3057995. Column 4, W..: 532, 29, 117, 912, 532, 274. The right end of this column is not visible as the table has reached its end. Upon joining, the third table titled the 'US States' is created. The table consists of seven columns and seven rows. The data given in the table are as follows: Column 1, OBJ: 1, 2, 3, 4, 5, 6. Column 2, Shape: Polygon, Polygon, Polygon, Polygon, Polygon, and Polygon. Column 3, NAME: Hawaii, Washington, Montana, Maine, North Dakota, South Dakota. Column 4, STATE underscore FIPS: 15, 53, 30, 23, 38, and 46. Column 5, POP 2000: 1211537, 5894121, 902195, 1274923, 642200, 754844. Column 6, POP… (not visible,: 13… (not visible), 6756150, 983932, 1338645, 662194, 827263. The two invisible cells are hidden as a box reading ‘Joined table’ is present on them. Column 7, header is not visible: 294102, 4821823, 817229, 1236014, 593181, and 669404.
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Spatial joins - Text Alternative
The first illustration of the target feature class shows a pink cylinder labeled cities and a pink blank sheet. The second illustration of the join feature class shows a green cylinder labeled airports and a green blank sheet. The third illustration of the output feature class shows a pink cylinder labeled cities2 and the empty pink and green sheets joined to form a single structure.
Intersection: intersect, proximity: within a distance geodesic and containment: contains. Intersection: Intersect 3 D, proximity: within a distance, and containment: completely contains. Intersection: Are identical to, Proximity: within a distance 3 D; and Containment: contains Clementini. Intersection: Boundary touches, proximity: closest geodesic; and containment: within. Intersection: Share a line segment with; proximity: closest; and containment: completely within. Intersection: crossed by the outline of having their center in; proximity: closest; and containment: within Clementini.
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Spatial join using intersect - Text Alternative
The illustration shows an aerial view of what appears like a map. The map consists of several zones represented in different colors. The first table titled Parcels consists of five rows and five columns. The data given in the table are as follows: Column 1, BLOC: A, B, 8, C. Column 2, LOT: 2, 2, 22, 2. Column 3, ADDRESS: 614, 205, 402, and 205. Column 4, STREET underscore NAM: BISSONNET, CROSLIN, BLACKSON, and O DELL. Column 5, PARCEL underscore ID: 0234111302, 0232120702, 0231140418, and 0232120902. The second table titled Zoning consists of five rows and three columns. The data given in the table are as follows: Column 1, Zone: Residential L, Residential L, Residential H, Residential L. Column 2, Setback: 10, 10, 5, 10. Column 3, Tax Rate: 0.5, 0.5, 0.6, 0.5. The first and second tables are joined together to form the third table which has a single structure.
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Spatial join using proximity - Text Alternative
Part a consists of three tables. The first table has two columns and six rows. The data given in the table are as follows: Column 1, Name: Adair Village, Adams, Adrian, Albany, and Aloha. Column 2, POP2007: 594, 309, 144, 44957, 48048. The second table has two columns and six rows. The data given in the table are as follows: Column 1, Name: Astoria Regional, Eastern Oregon Regional, Klamath Falls International, Mahlon Sweet Field, Mcnary field. Column 2, Type: Regional, Regional, International, Blank, Blank. The first and second tables join together to form the third table with five columns and six rows. The data given in the table are as follows: Column 1, Name: Adair Village, Adams, Adrian, Albany, and Aloha. Column 2, POP2007: 594, 309, 144, 44957, 48048. Column 3, airports underscore NAME: Mcnary Field, Eastern Oregon Regional, Eastern Oregon Regional, Mcnary Field, Portland Intl. Column 4, TYPE: Blank, Regional, Regional, Blank, International. Column 5, Distance: 31539, 23161, 258469, 31420, 24056. Part b shows a map of an area with seven plane symbols at various locations and tiny plots scattered all over the map. Part c shows the same map of Part b with seven plane symbols at various locations. The tiny plots are relatively larger in this map and are scattered all over it.
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Spatial join using containment - Text Alternative
The gradient map consists of regions represented by different colors. The areas of light brown color are marked as ‘Qt.’ Three plots, 800, 836, and 839 are located on the map. The first table titled ‘Septics’ consists of four columns and four rows. The data given in the table are as follows: Column 1, ID with a star symbol: 800, 836, and 839. Column 2, cntycode: 453, 453, 453. Column 3, basin: 14, 14, 14. Column 4, gma: 8, 8, 8. The second table titled ‘Geology’ consists of two columns and four rows. The data given in the table are as follows: Column 1, LABEL: Kpg, Knb, Qt. Column 2, NAME: Pecan Gap Chalk, Navarro Group, Terrace deposits. The first and second tables join to form the third table consisting of a single structure. The data given in the table are as follows: Column 1, ID: 800, 836, and 839. Column 2, cntycode: 453, 453, 453. Column 3, basin: 14, 14, 14. Column 4, gma: 8, 8, 8. Column 5, LABEL: Qt, Knb, and Knb. Column 6: NAME: Terrace deposits, Navarro Group, Navarro Group.
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Comparison of operators - Text Alternative
The gradient map consists of regions represented by different colors. The areas of light brown color are marked as ‘Qt.’ Three plots, 800, 836, and 839 are located on the map. The first table titled ‘Septics’ consists of four columns and four rows. The data given in the table are as follows: Column 1, ID with a star symbol: 800, 836, and 839. Column 2, cntycode: 453, 453, 453. Column 3, basin: 14, 14, 14. Column 4, gma: 8, 8, 8. The second table titled ‘Geology’ consists of two columns and four rows. The data given in the table are as follows: Column 1, LABEL: Kpg, Knb, Qt. Column 2, NAME: Pecan Gap Chalk, Navarro Group, Terrace deposits. The first and second tables join to form the third table consisting of a single structure. The data given in the table are as follows: Column 1, ID: 800, 836, and 839. Column 2, cntycode: 453, 453, 453. Column 3, basin: 14, 14, 14. Column 4, gma: 8, 8, 8. Column 5, LABEL: Qt, Knb, and Knb. Column 6: NAME: Terrace deposits, Navarro Group, Navarro Group.
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Cardinality and spatial joins - Text Alternative
The target table is titled ‘States’ and consists of three columns and eight rows. The data given in the table are as follows: Column 1, Shape: Polygon, Polygon, Polygon, Polygon, Polygon, Polygon, and Polygon. Column 2, STATE underscore NAME: Hawaii, Washington, Montana, Maine, North Dakota, and South Dakota. Column 3, STATE underscore FIPS: 15, 53, 30, 23, 38, and 46. The join table is titled ‘Counties’ and consists of three columns and eight rows. The data given in the table are as follows: Column 1, Shape: Polygon, Polygon, Polygon, Polygon, Polygon, Polygon, and Polygon. Column 2, NAME: Lake of the Wood, Ferry, Stevens, Okanogan, Pend Oreille, Boundary, Lincoln. Column 3, STATE underscore NAME: Minnesota, Washington, Washington, Washington, Washington, Idaho, and Montana. Column 4, FIPS: 27077, 53019, 53065, 53047, 53051, 16021, 30053. The rows 3 to 6 from column 1 to column 3 of the join table are outlined and directed towards the second row of the target table.
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Managing cardinality - Text Alternative
The first illustration represents Input features. Three round structures representing Join features lead to a single round structure representing the target feature. The second illustration represents Multiple copies join type. Three round structures representing Join features lead to three round structures representing target features individually. The third illustration represents the Merge rule join type. Three round structures representing Join features merge to form a single round structure representing a join feature. The single join feature leads to a single round structure representing the target feature.
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Join types - Text Alternative
The first illustration represents Input features. Three round structures representing Join features lead to a single round structure representing the target feature. The second illustration represents Multiple copies join type. Three round structures representing Join features lead to three round structures representing target features individually. The third illustration represents the Merge rule join type. Three round structures representing Join features merge to form a single round structure representing a join feature. The single join feature leads to a single round structure representing the target feature.
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Cardinality of parcels and zones - Text Alternative
One end of the illustration is labeled Parcels while the other end is labeled Zoning. The illustration shows an aerial view of what appears like a map. The map consists of several zones represented in different colors such as pink, orange, yellow, and blue.
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Cardinality of cities and airports - Text Alternative
The illustration shows a map of an area with seven plane symbols present at various locations. Tiny plots are scattered all over the area on the map. The plane symbols represent airports while the plots represent cities.
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Cardinality of septics and geology - Text Alternative
The gradient map consists of regions represented by different colors. The areas of light brown color are marked as ‘Qt.’ The area in a relatively darker brown is marked as ‘Knb.’ Three plots, 800, 836, and 839 are located on the map.
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Cardinality of highways and soils - Text Alternative
The gradient map consists of regions represented by different colors. Several pathways are located on the map along with plots such as 730, 84, 207, 74, 206, and 207.
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Merge rules for a one to one join - Text Alternative
The gradient map consists of regions represented by different colors. Several pathways are located on the map along with plots such as 730, 84, 207, 74, 206, and 207. The table consists of eight columns and six rows. The data given in the table are as follows: Column 1, Join underscore Count: 3, 3, 3, 3, 3, 2. Column 2, TARGET underscore FID: 638, 665, 676, 681, and 640. Column 3, HWY: 206, 74, 207, 74, 206. Column 4, MUID: OR148, OR153, OR153, OR160, OR160. Column 5, CLAY: 23.3; 9.6; 9.6; 15.8; 17.9. Column 6, SLOPE: 23.3; 9.1; 9.1; 5.8; 8.2. Column 7, HYDGRP: D, B, B, B, B. Column 8, HYDJOIN: D, C, C; B, B, B; B, B, B; B, B, C; B, C. Column 8 is outlined.
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Classic overlay 1 - Text Alternative
The three maps of South Dakota show different information. All three maps lay horizontally one after the other. The first map is labeled 'Slope class' consisting of blue gradients. The second map is labeled competence consisting of yellow gradients. The third map is an overlay of competence and 'Slope class' which appears to be a collage of the first two maps. The menu box titled ‘geohazard – White River Gr…’ shows the following data: OBJECTID: 2788, FID underscore SD geology: 104, Symbol: Tw, Infiltration: Low, Competence: Low, Unit Name: White River Group, Rock Type: Siltstone, FID underscore Slope class: 1937, and Slope class: 1.
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Classic overlay 2 - Text Alternative
The three maps of South Dakota show different information. All three maps lay horizontally one after the other. The first map is labeled 'Slope class' consisting of blue gradients. The second map is labeled competence consisting of yellow gradients. The third map is an overlay of competence and 'Slope class' which appears to be a collage of the first two maps. The menu box titled ‘geohazard – White River Gr…’ shows the following data: OBJECTID: 2788, FID underscore SD geology: 104, Symbol: Tw, Infiltration: Low, Competence: Low, Unit Name: White River Group, Rock Type: Siltstone, FID underscore Slope class: 1937, and Slope class: 1.
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Types of overlay - Text Alternative
Attributes joined intersect, input 1 a rectangle with two diagonal lines, input 2 a concentric circle, and output a concentric circle with two diagonal lines. Attributes joined the union, input 1 a rectangle with two diagonal lines, input 2 a concentric circle, and output a concentric circle inside the rectangle with two diagonal lines.
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Union example 1 - Text Alternative
The menu box titled ‘geohazard – White River Gr…’ shows the following data: OBJECTID: 2788, FID underscore SD geology: 104, Symbol: Tw, Infiltration: Low, Competence: Low, Unit Name: White River Group, Rock Type: Siltstone, FID underscore Slope class: 1937, and Slope class: 1. The second illustration shows the map of the Black Hills National Forest. The background of the area is orange while the surface consists of several streaks of red. A few locations are marked in tiny pink polygons. The third illustration shows a map of the Black Hills National Forest. The areas are represented in three different colors, yellow, orange, and red. The map legend states the following: Yellow: Sink, Orange: Rockfall, Red: Landslide.
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Union example 2 - Text Alternative
The first map shows areas represented in brown, yellow, and green. The map is labeled Elevation range. The second map shows areas represented in violet on a white background. The map is labeled Limestone. The third map shows several minute areas represented in green on a white background. The map is labeled Dense conifer. The fourth map shows areas represented in light yellow and violet with several minute areas in dark pink. All three areas in different colors are located on a white background. The map is labeled Snail habitat. After the third map is a right arrow that points towards the fourth map. The fourth map appears to be a collage or overlay of firth three maps.
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Intersection and geometry - Text Alternative
The first map consists of several regions represented in gradients of blue and green. On the surface of the areas, several streaks in dark blue are located. The second map consists of several regions represented in solid colors. Several tiny, rhombus-shaped plots are present in various locations of the region.
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Intersection output geometries - Text Alternative
Part a shows two shaded circles intersecting one another. This produces the shaded-intersecting part devoid of the circles, non-shaded intersecting part, and the two end plots of the intersecting part. Part b shows two streaks of blue and orange intersecting at one segment. This produces the streak of the intersecting segment and the plots of the streak on either end. Part c shows a shaded circle within several black streaks. This produces plots around the circumference of the circle and one section of the streaks.
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Comparing extraction and overlay - Text Alternative
Attributes joined intersect, input 1 a rectangle with two diagonal lines, input 2 a concentric circle, and output a concentric circle with two diagonal lines. Attributes joined the union, input 1 a rectangle with two diagonal lines, input 2 a concentric circle, and output a concentric circle inside the rectangle with two diagonal lines. Attributes not joined, clip input 1 a rectangle with two diagonal lines, input 2 a concentric circle, and output a circle with two diagonal lines. Attributes not joined, erase input 1 a rectangle with two diagonal lines, input 2 a concentric circle, and output a circle inside the rectangle with four lines on the corners to the circle.
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Data quality in spatial analysis - Text Alternative
The illustration of the map shows an unnamed location. The map consists of several areas represented in different colors. A pink region towards the left is labeled as Tract. A red pathway on the tract region is labeled as slivers. The tract region is separated from other areas by a county boundary. One of the areas consists of a circular mark which is labeled s XY tolerance.
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Using an XY tolerance - Text Alternative
The illustration of the map shows an unnamed location. The map consists of several areas represented in different colors. A pink region towards the left is labeled as Tract. A red pathway on the tract region is labeled as slivers. The tract region is separated from other areas by a county boundary. One of the areas consists of a circular mark which is labeled s XY tolerance.
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Areas and lengths - Text Alternative
The three maps of South Dakota show different information. All three maps lay horizontally one after the other. The first map is labeled 'Slope class' consisting of blue gradients. The second map is labeled competence consisting of yellow gradients. The third map is an overlay of competence and 'Slope class' which appears to be a collage of the first two maps. The dialogue box is titled ‘Calculate Geometry Attributes.’ Under the title, two major options Parameters and Environments are given. The option ‘Parameters’ is selected. Under ‘Parameters,’ options such as Input features: streets, Geometry Property, Length Unit: Miles (United States), and Coordinate system: NAD underscore 1983 underscore State Plane underscore Texas underscore Central underscore along with the globe icon are given. Under the option ‘Geometry Property,’ two options such as ‘Target field’ with a dropdown icon and ‘Property’ are given in the same row. Below the Target field, two drop-boxes, MILES and blank are given. Below Property, two drop-boxes, Length, and blank are given.
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Setting up a join 1 - Text Alternative
Cd114. District 0101, state AL, name Bradley Byne, and Party republican. District 0102, state AL, name Martha Roby, and Party republican. District 0103, state AL, the name Mike Rogers and Party republican. Quakehis. State MO, deaths 7, damage 0, MAG 7.88, MMI, 12, and LOC – incomplete. State, SN, deaths 51, damage 0, MAG 7.36, MMI 12, and LOC – incomplete. State, AK, deaths 0, damage 0, MAG 8.15, MMI 11, and LOC incomplete.
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Setting up a join 2 - Text Alternative
Parameters: Target features Cd114. Join features, quakehis. Output feature class, quake impacts. Join Operation, join one-to-one. Checkbox labeled keep all target features checked. Field map of join features. Output fields. Last name, party, semi, shape length, shape area, state, depth, deaths, damage, MAG, MMI, match option intersect, search radius, and meters. Source properties, merge rule sum, quakehis deaths, add a new source.
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The join result - Text Alternative
The table consists of eight columns and nine rows. The data given in the table are as follows: Column 1, Join underscore Count: 0, 0, 0, 1, 4, 1, and 29. Column 2, TARGET underscore FID: 1, 2, 3, 4, 5, 6, 7, 8. Column 3, DISTRICT: 0101, 0102, 0103, 0104, 0105, 0106, 0107, and 0200. Column 4, STATE: AL, AL, AL, AL, AL, AL, AL, AK. Column 5, NAME: Bradly Byrne, Martha Roby, Mike Rogers, Robert B. Aderholt, Mo Brooks, Gary J. Palmer, Terri A. Sewell, Don Young. Column 6, Party: Republican, Republican, Republican, Republican, Republican, Republican, Democrat, Republican. Column 7, DEATHS: <NULL>, <NULL>, <NULL>, 0, 0, 0, 0, 125. Column 8, DAMAGE: <NULL>, <NULL>, <NULL>, 0, 0, 0, 0, 31100000.
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