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Spatial Data Model: Basic Data Types

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Spatial Data Model: Basic Data Types 2 basic spatial data models exist vector: based on geometry of points lines Polygons raster: based on geometry of – PowerPoint PPT presentation

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Title: Spatial Data Model: Basic Data Types


1
Spatial Data Model Basic Data Types
  • 2 basic spatial data models exist
  • vector based on geometry of
  • points
  • lines
  • Polygons
  • raster based on geometry of
  • grid cells (images, bitmaps, DEMs)

2
Vector Data
3
Vector Data Model
Points represent discrete point features
each point locationhas a record in thetable
airports are point features each point is stored
as a coordinate pair
4
Vector Data Model
Lines represent linear features
each road segmenthas a record in thetable
5
Vector Data Model
node
node
  • Lines start and end at nodes
  • line 1 goes from node 2 to node 1
  • Vertices determine shape of line
  • Nodes and vertices are stored as coordinate pairs

6
Vector Data Model
Polygons represent bounded areas
each bounded polygonhas a record in thetable
landforms and water are polygonal features
7
Vector Data Model
  • Points are discreet
  • Nodes
  • Vertices
  • Lines
  • Nodes
  • Vertices
  • Arcs
  • Closed area (Lines points ) polygons

8
Vector Data Model
Vector data formats available in ArcGIS ESRI
GeoDatabases ESRI shapefiles ArcInfo coverages
and libraries CAD files (AutoCAD DWG, DXF
microstation DGN) StreetMap files Spatial
Database Engine (SDE) data ASCII point coordinate
data Linear measure (route) data
9
Vector Data Model
ESRI Geodatabases Geodatabase can store many
files from many source formats 1st preferred
vector format in ArcGIS Rapid display Fully
editable (coordinate and tabular) in
ArcGIS Convenient storage format Data sets are
either point or line or polygon
10
Vector Data Model
  • ESRI shapefiles
  • 2nd preferred vector format in ArcGIS
  • Rapid display
  • Fully editable (coordinate and tabular) in ArcGIS
  • Simple in structure
  • Do not use arc-node topology
  • Connected lines do not necessarily share a
    common node
  • Adjacent polygons do not share common bounding
    arcs
  • Data sets are either point or line or polygon

11
Vector Data Model
Shapefile polygon spatial data model
  • less complex data model
  • polygons do not share bounding lines

12
Vector Data Model
ArcInfo coverages Commonly found format (due to
ArcInfo market dominance) Data model more
complex Display more slowly in ArcGIS Coordinate
data not editable in ArcGIS Polymorphic
(point/line/polygon/route/annotation/) Problemati
c OS file structure
13
Vector Data Model
ArcInfo coverage spatial data model
  • polygons share bounding lines
  • same topological rules can be built into
    Geodatabase

14
Vector Data Model
  • ASCII coordinate data
  • Easy to obtain from a variety of sources
  • GPS
  • Traverse (survey)
  • Direct reading
  • OS and application independent

15
Vector Data Model
Characteristics Features are positioned
accurately Shape of features can be represented
correctly Features are represented discretely
(no fuzzy boundaries) Not good for representing
spatially continuous phenomena Potentially
complex data structure (especially for polygons)
- can lead to long processing time for
analytical operations
16
Raster Data
17
Raster Data Model
origin is set explicitly cell size is always
known cell references (row/column
locations)are known cell values are
referencedto row/column location values
represent numerical phenomena orindex codes for
non-numerical phenomena
18
Raster Data Model
A few different types of raster data
  • digital elevation model (DEM)

19
Raster Data Model
Characteristics Rectangular grid of square
cells Shape of discrete polygonal features
generalized by cells Continuous (surface) data
represented easily Simple data structure
20
Raster Data Model
Good at representing continuous phenomena, e.g.,
Wind speed Elevation, slope, aspect Chemical
concentration Likelihood of existence of a
certain species Electromagnetic reflectance
(photographic or satellite imagery)
21
Ecological Applications Vol. 17, No. 2, pp.
508526. LINKING OCCURRENCE AND FITNESS TO
PERSISTENCE HABITAT-BASED APPROACH FOR
ENDANGERED GREATER SAGE-GROUSE Cameron L.
Aldridge and Mark S. Boyce
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Well_dst 10m cont. distance to nearest standing
energy well Rd_dst 10m cont. distance to
nearest road SB 10m cont. sagebrush cover
determined from a.p. Crop_dst 10m cont. distance
to nearest cultivated land pCrop 10m
cont. prop. of crop in a 1-km moving window
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Homework
  • Read getting data into ArcGIS Maps, displaying
    layers, changing layer display properties,
    project and data management, sample data,
    data export
  • Assignment 2. Introduction to GIS
  • (due January 22)
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