1. Physical Structure of GDB
Geodatabase
Feature datasets
Spatial Reference
Object classes, subtypes
Features classes, subtypes
Raster datasets
Rasters
Relationship classes
Geometric networks
TIN datasets
nodes, edges, faces
Planar topologies
Locators
Domains
Addresses, X.Y location
ZIP Codes, Place names
Validation rules
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2. Geometry of Features Geometry System (6) Components of Shape (3)
Geography, KHU,
Jinmu Choi
Geometry System (6)
Components of Shape (3)
Attributes of Geometry (2)
Geometry Construction (6)
Spatial Relationship (4)
Topological Operator (7)
Summary and Next…
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3. Geometry System
The geometry stored as a special field in a feature class called “shape”
There are two levels of geometry
Feature geometry
Points, multipoints,
polylines, polygons, envelop
Components of
feature geometry
Segments, paths, rings
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4. Points and Polylines Points and multipoints Polylines (multipolylines)
Point is x,y coordinate
Optional Z or M
To represent small features such as wells or survey points
Multipoints are unordered collections of points
Polylines (multipolylines)
Ordered collection of disjoint or connected paths
To represent linear features such as roads, rivers, and contours
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5. Polygons A collection of rings
Ordered by their containment relationships
Representing the geometry of all areal features
When rings are nested, they alternate between interior rings and island rings
Rings can be disjoint but cannot overlap
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6. Envelop To represent the spatial extent of a feature
A rectangle that spans the min. and max. coordinates of a geometry
Parallel to a coordinate system
All geometries have envelops
for rapid display
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7. Multipart Features
Line and polygon features can be created as single or multipart features (multiline and multipolygon)
Multipart features are composed of multiple shapes grouped into a single feature which has only one record in the feature class table
In a multipart line feature, the individual parts are called paths
In a multipart polygon feature, they are called rings
Both paths and rings are composed of segments
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8. Example of Multipart Features
Multipart line (multiline)
Disjoint of a river because of draught
Multipart polygon
The seven larger islands of Hawaii can be stored as a single feature
Area are completely contained within another area, such as an island in a lake
Multipoint feature
Create a feature class with multipoint type, not point type
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9. Components of Shapes
Segments, paths, rings are components of a Geometry (feature shape)
Rings
A path that is closed and has
an unambiguous inside and outside
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10. Segments
Consists of a start, an endpoint and/or a function defining a curve between the points
Line: a straight segment
Circular arc: a portion of a circle
Road curbs at street intersection
Elliptical arc: a portion of an ellipse
Section of a highway ramp
Bezier curve: a parametric curve defined by a set of third-order polynomials
Contours or streams: smoothly varying features
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11. Paths A sequence of connected segments
Segments in a path cannot be intersect
Paths contain combination of 4 segments types
Paths make up polylines
Road comprised of straight lines and circular arcs
When a line and a circular arc in a road join, they are tangent to each other
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12. Attributes of Geometries
Three optional attributes: z, m values, Point IDs
Vertical measurement with z values
You can assign a z value for each point in a point, multipoint, polyline, or polygon
Z values commonly represent elevation
A ridge line that can store individual elevations at each point is a profile along a surface
TIN
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13. Attributes of Geometries
Linear measurements with m values
Linear measurement is based on interpolated distances along paths
Examples, mileposting,
stationing along a road
or canal
Geometry system has the function to interpolate m values for x,y points along a path
Managing points with IDs
Each point collected with a survey instrument has a point number (Unique IDs)
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14. Point Construction 1 Along Angle Bisector Angle Intersection
Given a curve and a distance or ratio, a point is constructed along that curve
Angle Bisector
Given three points, bisects angle subtended by the three points
Angle Intersection
Given two points and angles, place a point at the intersection of the rays
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15. Point Construction 2 Deflection Deflection Intersection Offset
Given baseline, deflection angle, distance
Deflection Intersection
Given baseline and two deflection angles from start and end points
Offset
Given a path, a distance or ratio
along the curve, and
offset distance
Parallel
Given a straight line path, a reference point, and a distance a b
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16. Multipoint Construction 1
Circular Arc Points
Given a circular arc, return 4 points
Divide Equal
Given a curve and
integer number
Divide Length
Given a curve and a length
Implied Intersection
Given two segments,
place points the actual
or extended intersection
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17. Multipoint Construction 2
Intersection
Given two segments,
place points at the actual intersection
Tangent
Given a circular arc and a point
Three Point Resection
Given three points and two angles from a station point
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18. Line and Circular Arc Construction
Line Construct Angle Bisector
Given 3 points and length, bisect that angle and construct a line at that length
Construct Arc Distance
Given a center point, start point, arc distance, build arc in a clockwise direction
Others constructions: pp
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19. Splitting Lines
You can create new features by splitting existing line and polygon features
There are two ways to split a line feature
To split a line manually by clicking it at the point where you want to split it into two lines
To specify where to split a line based on a distance or percentage
With both methods,
the Shape_Length attribute
is automatically calculated
for each new line
To set new attributes,
split policies will be used
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20. Testing Spatial Relationships
Equals
Does the base geometry equal the comparison geometry?
Contains
Does the base geometry contain the comparison geometry?
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21. Testing Spatial Relationships
Within
Does the base geometry within the comparison geometry?
Crosses
Does the base geometry cross the comparison geometry?
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22. Testing Spatial Relationships
Disjoint
Does the base geometry disjoint from the comparison geometry?
Overlap
Does the base geometry overlap the comparison geometry?
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23. Testing Spatial Relationships
Touches
Does the base geometry touch the comparison geometry?
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24. Applying Topological Operator
Buffer: Given a geometry and a buffer distance
Clip: Given a geometry and an envelope
Convex hull: Given a geometry
Cut: Given a geometry and a cut curve
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25. Applying Topological Operator
Difference: only in the base, not in the comparison
Intersect: both in the base and comparison
Symmetric difference: Union but exclude intersect
Union: include all together
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26. Splitting Polygons - Cut
To split a polygon feature, you choose the Cut Polygon Features edit task
Then, manually draw a line cutting the polygon into two polygons
The Shape_Area attribute
is automatically calculated
for each new polygons
To set new attributes,
split policies will be used
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27. Combining Features - Merge
The Merge function combines selected line or polygon features into a single new feature
The lines or polygons being merged must exist in the same feature class
Original features are removed and replaced with the new feature for which you have to select which feature's attributes are retained
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28. Combining Features - Union
Union combines features stored in the same feature class or in different feature classes
Although the features may be from different feature classes, their geometry type must be the same, either line or polygon
The output of a Union is a new feature in the layer—the original features are preserved
The new feature has no user-defined attributes
To add the created feature to a new (empty) feature class, you will first need to create the new feature class
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29. Combining Feature - Intersection
As with Union, the result of combining features with the Intersect function is a new feature in the target layer
Intersect creates a new feature from the area where features overlap
In the same or different feature classes, they must be of the same geometry type, either line or polygon
The original features are maintained, and the new feature is created with no user-defined attributes
To add the created feature to a new (empty) feature class, you will first need to create the new feature class
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30. Auto-Complete Polygon
Auto-Complete Polygon to create a new polygon that shares boundaries with one or more existing polygons in the same feature class
To create the new feature
First, select the Auto-Complete Polygon task on the Editor toolbar
Then, draw the polygon boundaries that aren't shared
Auto-Complete Polygon can be used on only one polygon feature class at a time
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31. Summary Geometry system Components of shape Geometry construction
Feature geometry: points, multipoints, polylines, polygons, and envelop
Components of shape
Segments, paths, rings
Attribute of geometry: Z, M, point IDs
Geometry construction
Given line, point, angle….
Spatial Relationships
Equals, Contains, Within, Crosses, Disjoint, Overlap, Touches
Topological Operator
Buffer, Clip, Convex hull, Cut, Difference, Intersect, Union…
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32. Next… Lab. Creating and Editing Features in Geodatabase
Topology and Annotation
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