GUS: 0262 Fundamentals of GIS

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GUS 0262Fundamentals of GIS

• Lecture Presentation 4
• Vector Data Model
• Jeremy Mennis
• Department of Geography and Urban Studies
• Temple University

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Spatial Data Models
Raster exhaustive regular or irregular
partitioning of space associated with the field
view location-based Vector points, lines,
polygons associated with the object
view object-based
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Spatial Data Models
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Spaghetti Vector Data Model
Each point, line, or polygon is stored as a
record in a file that consists of that entitys
ID and a list of coordinates that define geometry.
For Points

• ID Coordinates
• 3,4
• 5,5

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1
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Spaghetti Vector Data Model
Each point, line, or polygon is stored as a
record in a file that consists of that entitys
ID and a list of coordinates that define geometry.
For Lines

• ID Coordinates
• (0,1), (3,4), (5,6)
• (3,1), (5,2), (4,3)

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Spaghetti Vector Data Model
Each point, line, or polygon is stored as a
record in a file that consists of that entitys
ID and a list of coordinates that define geometry.
For Polygons

• ID Coordinates
• (2,4), (4,3), (3,6) , (2,4),
• (3,1), (5,2), (4,3), (3,2), (3,1)

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Spaghetti Vector Data Model
Advantages simple efficient for display and
plotting Disadvantages inefficient for most
types of spatial analysis
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Vector Topologic Data Model
Composed of points, lines, and polygons Node a
point at the intersection of three or more
lines In addition to coordinate locations, the
topologic relationships among geometric features
are explicitly recorded
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Vector Topologic Data Model
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Vector Topologic Data Model
Planar Enforcement No two individual features
can overlap. There are no holes or íslands
that are not themselves features. Every feature
is represented as a record in the attribute
table.
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Vector Topologic vs. Spaghetti
Spaghetti can encode as 2 or 3 polygons (and
have 2 or 3 records in the attribute
table) Topologic must be encoded as 3 polygons
(and have 3 records in the attribute table)
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Triangulated Irregular Network (TIN)
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Triangulated Irregular Network (TIN)
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Hybrid vs. Integrated Approaches
Hybrid Approach stores spatial data and
attribute data in different data models
(typically relational data model for attribute
data and proprietary data structure for spatial
data). Integrated Approach stores spatial and
attribute data using the same data model
(typically using the relational data model in a
single RDBMS).
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ESRI Shapefile
Designed by ESRI for ArcView Implementation of
the spaghetti vector model An individual layer
stores a single type of geometry (i.e. point,
line, polygon) No topology (but it can be
calculated on the fly...) Draws relatively
fast Open file format
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ESRI Shapefile
Three primary files in a shapefile .shp, .shx,
and .dbf All files must share the same prefix
for one shapefile, e.g. road.shp, road.shx, and
road.dbf .shp stores the feature geometry
(binary) .shx index for .shp file .dbf
attribute data stored in dBASE format
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ESRI Shapefile
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ESRI Coverage
Designed by ESRI for ArcInfo Implementation of
the vector topologic data model Closed file
format Each coverage is a directory, with
numerous files that store feature geometry,
projection, registration, etc. Attribute data is
stored in a separate INFO directory, which stores
all attribute data for all coverages in its
parent directory.
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ESRI Geodatabase
Designed by ESRI for ArcGIS Integrated approach
implementing spaghetti vector data model in a
relational DBMS (for vector) RDBMS is powered by
Microsoft Jet (Access) or other DBMS Topology is
generated on the fly Supports versioning,
multi-user edits, client-server architecture,
other mainstream database functionality