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 GIS Project

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… GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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) GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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. 108-109 GIS Project

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 GIS Project

Testing Spatial Relationships Equals Does the base geometry equal the comparison geometry? Contains Does the base geometry contain the comparison geometry? GIS Project

Testing Spatial Relationships Within Does the base geometry within the comparison geometry? Crosses Does the base geometry cross the comparison geometry? GIS Project

Testing Spatial Relationships Disjoint Does the base geometry disjoint from the comparison geometry? Overlap Does the base geometry overlap the comparison geometry? GIS Project

Testing Spatial Relationships Touches Does the base geometry touch the comparison geometry? GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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 GIS Project

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… GIS Project

Next… Lab. Creating and Editing Features in Geodatabase Topology and Annotation GIS Project